FINAL TECHNICAL REPORT CONTRACT N° : FIKW-CT2000-00088 CALIXPART SELECTIVE EXTRACTION OF MINOR ACTINIDES FROM HIGH ACTIVITY LIQUID WASTE BY ORGANISED MATRICES PROJECT CO-ORDINATOR : Karine LIGER - Jean-François DOZOL CEA Cadarache (France) PARTNERS : F. Arnaud-Neu 1 , V. Böhmer 2 , B. Casensky 3 , A. Casnati 4 , J-F Desreux 5 , B. Gruner 6 , C. Grüttner 7 , J. De Mendoza 8 , G. Pina 9 , P. Selucky 10 , W. Verboom 11 , G. Wipff 12 1 ECPM Strasbourg (France) 2 Johannes Gutenberg Universität Mainz (Germany) 3 Katchem Ltd (Czech Republic) 4 Universita degli Studi di Parma (Italy) 5 University of Liège (Belgium) 6 Institute of Inorganic Chemistry (Czech Republic) 7 Micromod GmbH (Germany) 8 Universidad Autonoma de Madrid (Spain) 9 CIEMAT (Spain) 10 Nuclear Research Institute (Czech Republic) 11 University of Twente 12 Université L. Pasteur Strasbourg PROJECT START DATE : September 2000 DURATION : 40 months
Transcript
FINAL TECHNICAL REPORT
CONTRACT N° : FIKW-CT2000-00088
CALIXPART
SELECTIVE EXTRACTION OF MINOR ACTINIDES FROM HIGH ACTIVITY LIQUID WASTE BY ORGANISED MATRICES
ANNEX 1: List of compounds synthesised during the project 97
ANNEX 2: Synthesis Schemes from Mainz University 127
ANNEX 3: Extraction results from CEA Cadarache 132
ANNEX 4: Complexation studies (ECPM) 150
ANNEX 5: Novel Extractants (Micromod) 156
3
ANNEX 6: Publications, lectures, oral communications, posters and patent related to the contract 166
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1 AIMS OF THE PROJECT
1.1 INTRODUCTION The fission of uranium or more generally of transuranium elements in reactors is an important source
of energy. The spent fuels contain fissile and fertile residues of significant energy value and
radioactive products (alpha, beta, gamma emitters). The radiotoxicity of these fuels can last for
millions of years and reprocessing appears to be of great interest to:
recover plutonium and uranium in order to be recycled
optimise the conditioning of waste
Because of its high radiotoxicity, the spent fuel is stored for several years before reprocessing.
Reprocessing (PUREX process) consists in dissolution of the spent fuel in high concentrated nitric
acid and then in an extraction step of uranium and plutonium by tri-n-butylphosphate (TBP).
Acidic solution coming from the PUREX process contains minor actinides (Neptunium, Americium,
Curium) and 99% of the non gaseous fission products. Some of the radionuclides have long half lives,
mainly beta and gamma emitters (such as minor actinides, caesium, strontium).
The present strategy is to concentrate and vitrify these high level activity liquid wastes for disposal in
long term storage. Nevertheless, this treatment leads to large volumes of concentrate composed of
active and inactive salts (as the matrix).
An alternative strategy could be to separate the minor actinides and long lived fission products (such
as 90Sr, 137Cs) from these wastes and destroy them by transmutation. Hence, a large part of the initial
wastes could be directed to a subsurface repository and a very small part containing most of the long
lived radionuclides to be disposed of, after conditioning, in geological formation.
One way to separate long lived activity elements from high activity liquid wastes is to use liquid-liquid
extraction process using functionalised macrocyclic compounds and then back extract the
concentrated elements in deionised water.
1.2 SUMMARY OF PREVIOUS CONTRACTS Previous contracts were devoted to find selective extractants optimised to separate 90Sr and 137Cs from
high activity liquid wastes coming from the PUREX process.
Among all synthetised calixarenes, dialkoxy calix[4]arenes crown-6 fixed in the 1,3 alternate
conformation (see Figure I) display the highest distribution coefficients for caesium. Removal of 137Cs
is particularly of interest because of its long half life and its assumed high mobility in nuclear waste
repository.
5
OO
R
O O
O O
O O
R
Figure I. : dialkoxy calix[4]arenes crown 6
Removal of 90Sr using liquid-liquid extraction was obtained with high efficiency using calix[8]arenes
bearing diethyl amide units (see Figure II).
8
PhO
O
NEt
EtO
Figure II. : Octa amide calix[8]arenes
Concerning extraction of minor actinides, promising results were obtained using functionalised
calixarenes bearing CMPO moieties. Nevertheless, lots of work to optimise the extractant were still
needed.
Hence the purpose of the present contract is to focus on selective extractants for removal of minor
actinides from high activity liquid wastes. Specially, the main challenge is to find a molecules able to
separate minor actinides from lanthanides, as the chemical behaviour of these 2 classes of
compounds is similar. In addition, attention will be paid on the possibility of industrial use of the
extractant. As an example, the extractant should
resist to radiolysis and hydrolysis
be soluble enough to minimise the volume of organic phase needed
present a good affinity for actinides and very low affinity for lanthanides
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In this contract, promising compounds are expected to be tested on simulated effluent from PUREX
process and if conclusive, on real high activity liquid waste.
1.3 ROLE OF THE DIFFERENT GROUPS INVOLVED IN THE PROJECT
The project is composed of 13 partners, 3 of them (NRI, IIC and Katchem) having joined the contract
for the last 16 months.
The Figure III represents the collaboration between each team during the project.
Figure III. Organisation of the contract
1.3.1 Role of CEA CadaracheCadarache coordinated the project and also tested the extraction ability of compounds synthesised by
the different teams. Hence, it helped to determine the ways of investigation to follow.
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Tests consisted in determination of distribution coefficients of different cations (Americium, Curium and
Europium) in order to find a selective extractant of minor actinides. Promising compounds were also
tested on simulated outlets from PUREX process. These measurements required implementation of
different analytical devices such as spectrometry alpha, spectrometry gamma, liquid scintillation and
ICP-MS.
1.3.2 Role of CIEMATThe role of CIEMAT was to verify the industrial interest of the promising molecules. Indeed,
extractants should not be sensible to hydrolysis and radiolysis. Hence, promising compounds were
sent to CIEMAT in order to test their resistance under hydrolysis and radiolysis. Tests consisted in
observing the effect of hydrolysis and high integrated gamma doses on the stability of selected
compounds. Attempts were made to identify degradation products and to quantify them.
1.3.3 Role of ECPMECPM performed complexation and extraction studies on molecules sent by the different teams
involved in synthesis tasks in order to acquire basic knowledge on the coordination properties in
solution of the new ligands synthesized towards lanthanides. The three lanthanides La3+, Eu3+ and Yb3+
were chosen as representative cations of the series and could also be considered as models for
trivalent actinides.Determination of complexes stoichiometry was also done and stability constants
were measured when the extraction was efficient.
1.3.4 Role of IICThe role of IIC was to synthesise new extractants linking cobalt bis(dicabollide)(1-) ion closo-[(1,2-
C2B9H12)-3,3’-Co]- (COSAN) to different functionalised calixarenes or cavitands, having initially a low
extraction ability but an interesting selectivity.
Indeed, the role of COSAN anion is to reduce or compensate the charge of the target cation on a short
distance within single complex particle. The resulting charge compensation would minimize the Gibbs
energy necessary for the cation transfer to the low polar organic phase.
COSAN starting materials were synthesised by Katchem and functionalised platforms were provided
by Mainz, Twente and Parma.
All the compounds synthesised were sent to NRI for extraction tests.
1.3.5 Role of KatchemKatchem has provided starting materials (i.e. parent COSAN or COSAN dioxanate…) to IIC group for
attachment on functionalised platforms.
1.3.6 Role of LiègeLiege has used crystallography and NMR spectroscopy to elucidate the structures of calixarene
metallic complexes. The aggregation of extracted complexes has been investigated by measuring the
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nuclear magnetic relaxation dispersion (NMRD) of organic solutions of calix[4]arenes synthesized by
Mainz University. These solution studies have been carried out in collaboration with ULP (stability
constants and quantum modeling). Furthermore, the Liege team has synthesized calixarenes
substituted by various sulfur containing functions. Extraction results have been collected for these
macrocyclic ligands and their monomeric analogues.
1.3.7 Role of MadridThe role of Madrid was to synthesised functionalised calix[6],[8]arenes bearing malonamide and
diglycolamides ligands under different conformation. The compounds obtained were sent to CEA
Cadarache for extraction tests.
1.3.8 Role of MainzMainz university prepared several calix[4]arenes bearing CMPO or mixed ligating sites under different
conformation. Mainz also focused on dendrimers bearing CMPO or functionalised calix[4]arenes,
which were the basis of a patent filed by CEA Cadarache.
In collaboration with Micromod, Mainz has also developed magnetic particles covered with moieties or
functionalised platforms.
All the compounds synthesised were sent to CEA Cadarache for extraction tests.
1.3.9 Role of MicromodMicromod synthesised new kind of extractants based on magnetic particles coated with a ligand. The
synthesis is done in collaboration with the partners involved in synthesis works and who provided
starting materials which Micromod can graft on particles. The novel extractant obtained were sent to
Cadarache so that extraction ability could be tested through liquid-solid extraction process.
1.3.10 Role of NRIThe role of NRI was to perform extraction tests on compounds containing COSAN and synthesised by
IIC (in collaboration with Katchem, Twente, Parma). Tests consisted in determination of distribution
coefficients of different cations (Americium, Europium) in order to find a selective extractant of minor
actinides.
1.3.11 Role of ParmaParma university provided platforms (calix[n]arenes, CTV) bearing hard and/or soft donor groups, like
picolinamide, TTFA, CMPO…. All the compounds synthesised were sent to CEA Cadarache for
extraction tests. Parma group has also sent starting materials (compounds with poor extraction ability
but high selectivity) to IIC, in order to graft COSAN. The compounds coming from these collaborations
were sent to NRI for extraction tests.
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1.3.12 Role of Twente The Twente group focused on the design of rigid resorcin[4]arene-based cavitands and flexible
tripodal compounds bearing different ligating sites (mixed oxygen sulphur or sulphur sites). All the
compounds synthesised were sent to CEA Cadarache for extraction tests. Twente university has also
provided starting materials to IIC for COSAN attachment. The molecules coming from this
collaboration were sent to NRI to test their extraction abilities.
1.3.13 Role of ULPThe role of ULP was to analyse at the microscopic level some key factors which are involved in the
efficient and selective extraction of cations by suitable ligands, by using computer simulations
(molecular dynamics simulations or quantum mechanical studies). Interfacial phenomena, interactions
between cations and ligands and role of the solvent were invertigated to improve general knowledge of
the phenomenon taking part in extraction process.
1.4 COMPOUNDS STUDIED
More than 160 compounds were synthesised, combined and tested since the beginning of the
contract.
They are composed of ligands:
- CMPO - acylurea
- CMP - acylthiourea
- picolinamide - TTFA
- picolinthioamide - pyridine
- malonamide - mixed CMPO-acetamide
- glycolamide - mixed CMPO-picolinamide
- mixed picolinamide
diethylaminocarbonylmethoxy
- mixed CMPO-picolinthioamide
- mixed picolinthioamide
diethylaminothiocarbonylmethoxy
- mixed picolinamide
hydroxycarbonylmethylaminoethyloxy
- mixed CMPO
hydroxycarbonylmethylaminoethyloxy
- COSAN
Fixed on several platforms:
- Calix[4]arene - Magnetic beads
- Calix[6]arene - Dendrimer
- Calix[8]arene - Cyclotriveratrylene
- Cavitand
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Different conformation were also studied as well as the chain length between the platform and the
ligand.
The complete list of compounds synthesised during this contract is given in annex 1.
A list of publications, lectures and oral communications, posters and patent related to the contract is
given in annex 6.
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2 SYNTHESIS This part concerns results obtained by organisms devoted to synthesis of new extractants:
- Institute of Inorganic Chemistry dealing with covalent linking of COSAN on macrocycles
- Katchem Ltd providing COSAN synthons
- Madrid University synthesising malonamide and glycolamide derivatives
- Mainz University focusing on CMPO group attached on various basic skeletons alone and in
combination with other functional groups
- Parma University providing compounds based on hard and soft donor groups
- Twente University synthesising extractants based on cavitands and tripodal compounds.
2.1 COVALENT LINKING OF COSAN ON DIFFERENTS PLATFORMS ( I nstitute of Inorganic Chemistry )
IIC dealed with calixarenes and cavitands functionalised with cobalt bis(dicarbollide)ions, which
starting materials were provided by Katchem Ltd.
2.1.1 Development of the ionic calixarene-Cosan carriers Some of the calixarenes substituted with metal binding groups at the geometrically optimised sites
proved outstanding selective extraction of actinides from lanthanides. Even good selectivity actinide vs
lanthanide can be reached. The selectivity is done by incorporation of several selective groups on the
wide and/or narrow rim of the calixarene or cavitand platform, producing arrangement of several metal
binding moieties in the favourable geometric arrangement and distances. On the other hand, nature of
the calixarenes or cavitands corresponds to uncharged organic compounds. Hence, the resulting
metal complexes are always charged. This, in fact, effects inhered co-transport of nitrate ions together
with the metal cation during the extraction process, in the first or second coordination sphere of the
metal complex. Tests of the synergic effect of the Cobalt bis(dicarbollide) anions [(C2B9H11)2Co]-
(Cosan) (E178) on the extraction with modified calixarenes proved often positive effect. Cosans are
known as a powerful class of extraction agents, especially for Cs+ and Sr2+ radionuclides1. Recently,
under previous EEC Project IC15-CT98-0221, new extraction agents based on covalent bonding of
CMPO groups on COSAN were prepared2, which have been highly effective for the extraction of the
whole class of lanthanides and actinides, however without selectivity Ln vs. Ac. Creating novel anionic
molecules based on Cosan substituted calixarenes is expected to lead to qualitatively new properties,
i.e. better encapsulation of the metal inside the hydrophobic complex. Eventually, the solubility of such
species in NPOE and NPHE and other solvents and stability of the extraction system may be positively
changed. This can improve the efficiency of the process and minimize the costs.
The novel idea of combination of calixarene and COSAN was born from discussion between CEA,
Parma, Twente , Mainz and IIC Groups, before involvement of IIC in this Project in 2002. However
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practical implications raised from combination of two so different classes of compounds has not meant
trivial synthetic problems and the time to reach the results was relatively short. The synthetic
methodology has been based on the use of COSAN synthons with simple reactive functional groups.
These included [8-O(CH2CH2)2O(+)-1,2-C2B9H10)-(C2B9H11)] “COSAN-dioxane” (E181)3, [8-(n-BuNH2-
Figure IV. [8,8’-μ-CH2-O(CH3)<(1,2-C2B9H10)2-3-Co]- (E187)
Synthetic procedure to new reactive cobalt bis(dicarbollide) reagent [8,8’-μ-CH2-O(CH3)<(1,2-
C2B9H10)2-3-Co]- E187 has been recently developed (see Figure IV) under this Project. Acid catalyzed
condensation reaction of anion E178 with formaldehyde provide zwitterionic derivative with diatomic
bridge –O(+)(CH3)-CH2- between boron positions 8,8’ of the dicarbollide ligands in ca 45% yield.
Bridging group can be easily cleaved between -CH2- and –O- atom by a Lewis base L, similarly as that
of E181, but even milder conditions can be applied. Resulting products are typically 8-MeO-, 8’-CH2-L
derivatives. This provided new procedure useful in tuning up the distance calixarene-dicarbollide or
CMPO-dicarbollide in the applications bellow. Presence of the -OCH3 moiety in position B(8’) protects
the second most reactive site and may provide additional donor atom for metal bonding. The scaling
up of the preparative methods leading to synthons E181-E187 was tested in collaboration with
Katchem Ltd.
With the exception of t-bu-calix[4]arene, all calixarene and cavitand precursors were prepared and
supplied by three partners from University of Twente, University of Parma and JGU Mainz and the
peculiarities of the calixarene-COSAN chemistry were solved in close cooperation with these Groups.
The samples supplied by the three Groups included modified resorcin[4]arene cavitands and narrow
and wide rim calix[4]arenes with either OH, COOH or NH2 groups or groups bonded via spacer.
Those allowed study of the attachment of the COSAN on a longer or shorter distance. The list of
compounds is given in annex I.
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2.1.1.1 Calixarenes functionalized with COSAN anionic moieties
Synthetic study of methods for the covalent bonding of the COSAN on the calixarene platform was
performed using narrow or wide rim calixarenes or resorcin[4]arene cavitands with two and four
reactive sites available for bonding of COSAN supplied by all three above Groups and also on the
commercially available parent calix[4]arene. Resulting series of compounds has not contained other
selective groups on the platform, except the anion E178. However, their synthesis had to be
performed to accumulate sufficient experimental knowledge in the development of the appropriate
reaction conditions, set up product isolation procedures (e.g. analytical and preparative
chromatographic conditions), and better understanding of factors like the solubility characteristics,
solution behaviour, and effect in the NMR spectral patterns raising from combination from both
moieties.
Good results were obtained considering the reactions of the resorcin[4]arene cavitands from Twente
Group. Reactions of two obtained samples of E169 and E170, both containing four OH or -CH2OH
groups on wide rim carried out with E181 in the ratios 1:3 or 1:2, respectively. Similar reactions in the
1: 2 and 1:4 ratios were tested with sample E171 comprising hydroxy groups attached via longer
spacer on the narrow rim of the resorcin[4]arene cavitands. Only this type of bonding via
diethyleneglycol chain was studied due to limited amount of the chemicals available and high reliability
of this procedure proven for a large variety of the simpler substituents. Typical reaction conditions for
the cleavage of the dioxane ring were used, i.e. reaction of the cavitands deprotonized with NaH in
THF or DME. All reactions proceeded smoothly and the respective products in substatially pure form
were obtained after purification by multiple chromatography and characterized by NMR methods
(E108, E109, E110 and E111, see the Annex 1 and the Figure V). The relative easiness in isolation of
the products can be attributed to the rigidity of the resorcin[4]arene-cavitand platform with almost no
possibility of the conformational changes and a larger distance of the bonding sites in comparison with
the respective calix[4]arene molecules. This apparently decreases the steric strain or ion repulsion,
and according to NMR results, allows also for bonding of more than two Cosan moieties on the
platform. Compounds E109, E110 from this series containing two Cosan anions and two unsubstituted
OH groups can eventually serve for attachment of organic metal binding moieties.
Figure V. : Synthesis of E110
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Grafting of COSAN on the calixarene wide rim was tested using two samples of the calix[4]arenes
functionalised with two (in positions 1,3) or four COOH groups from Parma University. Carboxilic
groups were converted to acylchloride derivatives using known procedure supplied by Parma Group
with the chemicals. The 1,3-dichloride was reacted with bridged H2N(1,2-C2B9H10)2-3-Co] E182 and
non bridged E185 aminoderivatives of Cosan under variety of reaction conditions. Good reaction
conditions were found after discussion with Parma Group, and the coupling of Cosan via amidic bonds
to the calixarene platform was achieved. Compound substituted with two Cosan moieties was
successfully obtained in the reasonable yield as the main product from the reaction of the former
derivative, along with a minorite quantity of monosubstituted product (E115, see Figure VI, and E114)
from the list of compounds. Both compounds were characterized by NMR and Mass Spectrometry.
Similar reaction with the E185 was more difficult to carry out and apparently, only poorly characterised
monosubstituted product (E116) resulted based on the NMR evidence only. Reactions of the tetraacid
or its respective chloroderivative led under variety of the reaction conditions to rich mixtures of
products unseparable by chromatographic methods. Probably too high steric crowding can be
assumed as preventing tetrasubstitution in good yield.
Figure VI. Synthesis of E115
Development of the reaction condition and methods for product isolation arising from narrow rim
calix[4]arene class of compounds has been comparatively the most difficult task in the series.
Substitution on the narrow rim calixarenes were studied on the 1,3-dipropoxy-calixarene[4] supplied by
University at Mainz as the model compound containing 1,3 sites blocked with propyl groups. This is
known to limit conformational flexibility. First reactions were carried out with the new boron synthon
E187 and the almost pure disubstituted main product in cone conformation with two Cosans attached
by CH2- moiety was obtained as the main product, after tedious purification procedure. The possible
explanation of the encountered difficulties has been found only very recently upon summarizing the
experimental and spectral evidence from the wider interplay with the reaction conditions and isolation
and characterization of the products from the reactions with synthon E181. It lies in the conformational
changes under the reaction conditions and presence of several conformers in the product mixture
which was difficult to separate due to the dinegative charge of the compounds. Reaction of the 1,3-
dipropoxy-calix[4]arene with E181 in the ratio 1:2 led to the mixture of two products in the ratio equal
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almost to 1:1 (see Figure VII). The first product was isolated by multiple chromatography in
substantially pure form and characterized by its NMR as the calixarene substituted with two Cosan
anions in cone conformation (E113A). Second almost pure compound was obtained by crystallization
of Cs+ salts from the chromatographically enriched fractions and its NMR spectrum can be assigned to
the COSAN disubstituted calixarene in the 1,3-alternate conformation (E113B). The conformational
changes proceeded even under relatively mild reaction conditions at lower temperatures and hence, it
seems to difficult to eliminate them.
Figure VII. Synthesis of E113A and E113B
Presence of the conformational changes created also problems in the isolation of pure products from
the reactions of unsubstituted calix[4]arene attempted with Cosan-dioxane E181 in various ratios 1:1
to 1:4 in course of the first experiments carried out under this Project (E112). On the other hand,
surprisingly, recent application of milder reaction conditions, which have been developed in the
meantime after discussion with Mainz Group, led to smooth formation of the Cosan 1,3-disubstituted
parent calixarene in the cone conformation in very good yield and purity after re-crystallization (E112).
Comparison of this and above results indicates that even presence of propoxy group at the narrow rim
may promote rather than blocks change of conformation due to higher steric overcrowding or ionic
repulsion. On the other hand, no conformational changes were observed for the Cosan substituted
products changing the counter cations or heating these compounds in solution or as solids up to
100oC. Last product will be available easily in multigram quantities and can be considered to serve
directly for the subsequent introduction of metal binding groups due to presence of two available
bonding sites (see Figure VIII).
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Figure VIII. : Sythesis of E112
Several samples from the above series were supplied to NRI (see Annex 1) to study their solubility in
the common solvents used for extraction, their stabilities and extraction properties.
2.1.1.2 Bonding of Cosan on calixarenes and cavitands with metal selective groups
Several attempts were carried out to reach substitution of the resorcin[4]arene or calix[4]arene
molecules with CMPO groups already attached at the platform.
Two compounds of this class containing amino groups for COSAN attachment were supplied by
JGUM Mainz. Sample E167 contained two CMPO moieties and two NH2 groups, attached to the
narrow rim calix[4]arene via n-butyl spacer. Second calixarene sample E168 had three CMPO groups
bonded and one free NH2 group attached directly to phenyl ring at the wide rim of the calix[4]arene
molecule. First, model reactions were carried out using starting material E181. The respective samples
(E141, E142) were isolated by multiple chromatography, but their purities remained dubious.
Reactions with the [8,8’-μ-P(O)Cl<(1,2-C2B9H10)-3-Co]- E186 as the Cosan synthon were attempted to
create anionic compounds more suitable for extraction purposes. According to NMR results, the
products contained Cosan bonded on the calixarene platform, however, these reactions led always to
complex mixtures of products and difficulties in their separation and characterization. Only poorly
defined species resulted (E143). Considering the larger number of binding sites available in such
platforms inclusive acidic sites at CMPO moiety, this seems to be an inevitable problem. Indeed, in
some instances, NMR signals corresponding to CMPO moiety were affected by substitution. Most of
the above samples proved good Eu3+ extraction properties from 1M nitric acid, according preliminary
extraction tests at NRI. This seems to indicate good potential of such compounds.
However, is seems that the issue of perfect purity cannot be solved without changing the overall
reaction scheme. Scheme designed with JGUM Mainz includes (see Figure IX) : i. bonding of two
protected amino group on the narrow rim calix[4]arene, ii. reactions of E181 or E187 synthons with
two remaining OH groups at the platform, iii. de-protection, iv. reaction of the NH2 groups with the
reactive nitrophenylester of the phosphorylacetic acid to introduce two CMPO groups.
Study of this approach is currently in progress. The narrow rim calixarene with two phtalimido groups
was reacted with Cosan-dioxane synthons E181 and E187 to obtain longer and shorter connection.
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However, yields of the respective bonded products were low, especially for the second case, where
ring of E187 was cleaved mostly without bond formation and salt composed of a protonized calixarene
cation and Cosan anion resulted as the main product. An interplay with the origin and bulkiness of
protective groups and dislocation of the OH groups outside of the platform or at the second rim would
be helpful to limit steric factors.
Co
O O
O
O
O OO O
PhtPhtCo
O O
Co
Co
O O
O
O
O OO O
NH HN
C O
P OPh
Ph
CO
PO
Ph Ph
OO
H(CH2)3
N
tButBu
OO
Co
5
3`3
i. n NaH, DME/Toluene, ambient temperature
ii.
5
2
2
2
LW-6
5
1,3-di-Pr-calix(4)arene
?
i. deprotection, H 2
N-NH 2.H 2
O
ii. NO 2
C 4H 4
-O-C(O)CH 2P(O)(C 6
H 5) 2
5
2
5
2-
Chart 1
(CH2)3(CH2)3
(CH2)3(H2C)3
Figure IX. Reaction scheme proposed by Mainz University
Another possible way is lies in the work up of the recently obtained 1,3-Cosan substituted calixarene
E112. This is considered to give the defined mixed substitution with CMPO and Cosan moieties after
three additional reaction steps (see Figure X).
Co
O O
O
O
O OO O
PhtPht
Co
Co
Co
O O
O
O
O OO O
NH NH
C O
P OPh
Ph
CO
PO
Ph Ph
O O
O
O
O OHHO O
Co
Co i. 2 NaH, DME/Toluene,
ii.
5
i. deprotection, H 2
N-NH 2.H 2
O
ii. NO 2
C 4H 4
-O-C(O)CH 2P(O)(C 6
H 5) 2
5
5
2-
Chart 2
5
5
21
5
R-DX-1-3
2 BrBuPht
Figure X. Reaction scheme proposed by Mainz University
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E112
Two samples of resorcin[4]arene cavitands which have four selective CMPO (E172) and ethylester of
thiourea (E173) at the lower rim and four OH groups at the opposite upper rim obtained from Twente
Group were modified by Cosan substitution. Due to limited amount of the starting material (82 and 46
mg), only one reaction in the ratio 1:2 was tested for each particular derivative. E172 was reacted with
E187 (see Figure XI) and E173 with E181 under mild conditions to create compounds with shorter and
longer bond of the Cosan to the platform. A relatively cleaner reactions were observed, which can be
attributed to the presence of the reactive sites at the opposite rim of the cavitand and their bonding on
a larger distance from the platform. Compounds (E139 and E140) were isolated from these reactions
and characterized by NMR. However, a need for their better characterization by other methods still
persists. Samples were submitted to NRI for the extraction tests.
Figure XI. Synthesis of E139
2.1.2 New Progress in the Cosan-CMPO-like compoundsBefore the end of the previous Project, IIC has developed synthetic route to bridge substituted anion
E178 derivative of the formula [(8,8’-Ph2P(O)CH2C(O)N<(1,2-C2B9H10)2-3-Co]- (R7)2. The known and
readily available bridged zwitterionic amino derivative E182 was used as the starting material in the
synthesis. Bridging >NH2 groups of this series of compounds are prone for easy substitution by a
variety of organic groups. Typically, zwitterionic, charge neutral, compounds are formed in the amine
derivative series. Such bi-polar compounds are considered as not suitable for extraction. In contrast,
the nitrogen atom of the amidic moiety does not tend to be protonized and the cobalt bis(dicarbollide)
(1-) charge is preserved. Resulting compound exhibited good extraction properties for Eu3+. In
comparison of the previous series of anion E178 derivatives, where whole “classical” CMPO moiety
was bonded via longer chain, this compound allows easier re-extraction. The molecular structure of
Cs+ salt was determined by single crystal X-Ray diffraction under this Project. In this structure (see
Figure XII), the almost linear chain of cesium atoms is surrounded with anionic ligands, which form
19
E172
walls of a channel structure. Cs+ cations are coordinated to oxygen atoms via P(O) and C(O) groups.
Interesting is the almost perpendicular position of two sets of phenyl rings of the diphenylphosphine
moiety, which may account for complete repulsion of the hydratation water of the cations from the
metal coordination sphere.
Figure XII. Structure of the complex form with Cs+
Considering the extraction properties, more interesting is the molecular structure of the (R7)3Eu3+
complex. Unfortunately, the structure could not be fully refined due to asymmetry of the nitrogen
substitution and presence of both, dextrorotary and levorotary arrangement of terminal phosphine
oxide phenyl substituents in the crystal. On the other hand, arrangement around the central metal
atom could be clearly resolved. A 3:1 complex resulted (see Figure XIII), in which Eu3+ atom is tightly
coordinated to six P(O) and C(O) functionalities. Three molecules of water complete the coordination
number 9. Important feature is the ability of the anionic ligand to displace completely the nitrate ions
from the metal primary coordination sphere. This effect not observed in classical CMPO series is
apparently caused by inherent charge compensation by three Cosan anions present in the proximity of
the cation.
Figure XIII. : Structure of the (R7)3Eu3+ complex
Similar product of the reaction of asymmetric aminoderivative E183 has been studied for comparison.
This has been carried with the aim to prove if mixture E182 and E183, arising from the same reaction,
could be eventually used as whole without isolation of particular isomers, if some need for larger scale
production arises. Surprisingly, [(4,8’-(Ph2P(O)CH2C(O)N) < (1,2-C2B9H10)2-3,3’-Co]- R7 proved
significantly increased extraction properties (DEu 602 from 1M HNO3, 0.01M extractant in toluene).
The reason for this behaviour is still not known. Unfortunately, the crystals of Eu3+ complex obtained
were disordered. Possible formation of B(8’)-HM bonds may account for a stronger metal bonding.
20
The compounds R7 and E117 represent first members of novel family, where the “classical” CMPO
molecule was modified by a substantial manner (i.e. the ionic boron cage forms an inherent part of this
moiety). Bridge substituent gives rise to stable rigid arrangement around the nitrogen atom. This is
reflected in an easier crystallization and purification and blocks the most reactive sites of the cobalt
bis(dicarbollide) ion otherwise prone to attack by the nitric acid in the extraction process. The
extraction ability is about three orders of magnitude higher than for the best “classical” CMPO
extractants and is still higher than that found for synergic mixtures of CMPO and brominated cobalt
bis(dicarbollide). For compound R7 these decrease steeply, indicating an easier back-extraction than
in the previous series of compounds with spacer-bonded CMPO.
The new CMPO-like derivatives (E118 and E119) were synthesized based on the new boron reagent
E187 using two-step procedure. These compounds were submitted to extraction tests at NRI. Only
compound E119, where R´= benzyl, proved good extraction properties for M3+ and forms alternative to
two previously prepared Cosan-CMPO series.
2.1.3 Conclusions Large synthetic effort has been spent to prepare mono- , di- COSAN calix[4]arene or di-, tri- and
tetra- functionalised cavitands. With the exception of parent calix[4]arene, all calixarene and cavitand
precursors were prepared and supplied by three partners from University of Twente, University of
Parma and JGU Mainz and discussions with these Groups were helpful for overcoming main
difficulties in this chemistry.
Collaboration of the synthetic Groups within the Project confirmed feasibility of COSAN anion
attachment on calixarenes and cavitands.
Various synthetic methods for the attachment were tested
Basics insight on the methods of preparation, isolation and purification of such supramolecular ionic
compounds was obtained along with preliminary information about solubility and extraction properties.
Compounds from both series of calix[4]arenes and resorcin[4]arene cavitands functionalised with
COSANs were prepared, even if, in some instances, need for their additional purification and
characterization, especially by M.S. persists.
Both, upper and lower rim substituted calixarenes were obtained. Several modes of bonding were
achieved using either long flexible spacer or shorter bonding.
The reactions performed on the resorcin[4] arene cavitands seemed to proceed relatively smoothly,
also the product isolations were easier. This is probably due to rigidity of this platform and a larger
diameter of the rim. More difficult seems to reach substitution at the narrow-rim calix[4]arenes,
apparently due to conformational changes and steric effects.
Substitution of the calix[4]arene modified with CMPO groups already prior bonding of Cosan has
proven to be difficult due to larger number of binding sites available in such molecule. Reactions with
such species lead to mixtures of products and difficulties in their separation. For this reason, model
reactions were studied on the 1,3-di-propyl-calix[4]arene supplied by JGU Mainz and expected
products were isolated. Reaction conditions were subsequently extended on 1,3-phtalimide protected
calixarene. The products are assumed to serve, after de-protection, for bonding of CMPO groups.
21
This synthetic knowledge shall serve for design of more sophisticated extractants – anionic
calixarenes functionalized with metal selective groups in the future.
Also some results belonging to chemistry of simpler Cosan derivatives for extraction purposes have
been obtained. To these belongs structural characterization of the previously studied bridged CMPO
species [(8,8’-(Ph2P(O)CH2C(O)N) < (1,2-C2B9H10)2-3,3’-Co]Cs, synthesis of the [(4,8’-
(Ph2P(O)CH2C(O)N) < (1,2-C2B9H10)2-3,3’-Co]- asymmetric isomer with higher extraction ability and [(8-
CH2R-1,2-C2B9H10)(8’-OCH3 –1’,2’-C2B9H10)-3,3’-Co]- (R= tolyl, benzyl) Later compound proved good
extraction properties for M3+ class.
22
2.2 SYNTHESIS OF BORANE CLUSTERS ( Katchem Ltd ) The main objectives of Katchem Ltd. in Calixpart project concerned:
Production and supply of currently commercially unavailable borane cluster materials to
individual project partners.
These materials were prepared in laboratory - scale quantities for research within the
scope of project.
Elaboration of large-scale preparation of selected materials for the testing.
Besides these basic tasks, Katchem Ltd. resolved a number of other tasks such as examining the
yields and reproducibility of the suggested synthetic procedures, suggesting a suitable analytical
method of identification and assessing whether the synthetic procedures provide unique products.
Katchem Ltd. has provided the samples specified below for research and tests within the framework of
project tasks, which have been gradually refined during the course of the project:
Tri Methylamonium 8,8’-μ-Phospho-oxychloride[commo-3,3’-cobalta-bis(1,2-dicarba-
closo-dodecaborane)]
(C6H5)2POCH2CO2-C6H4-NO2 (E188)
p-nitrophenylester of diphenyl phosphorylacetic acid
2.2.1 Preparation of Cosan Cs (E178)
40 g of solid NaOH were added to 43 g o-carborane dissolved in 250 ml of methanol. The temperature
of the reaction mixture was gradually increased, and after ca.15 min. the boiling point was reached
23
accompanied by the evolution of hydrogen gas. After ca.30 min. an homogeneous solution emerged,
which was heated for another 2 hours. 300 ml of water were then added and methanol was distilled
off. 70 g of CoCl2.6H2O in 100 ml of water were added to the continuously stirred solution.
Subsequently, 40 g of NaOH in 100 ml water and 40 g of solid NaOH were added stepwise. The
reaction mixture was stirred at 100°C for 1 hour, becoming cloudy due to the precipitation of cobalt
during this period. The reaction mixture was diluted with 200 ml of water and filtered with the
temperature at 50°C. The solid residue was washed twice with 50 ml of water at 50°C. The clear
orange filtrate was precipitated using 25,3 g of CsCl in 100 ml of water. After the suspension of the Cs
salt had been cooled to 50°C, it was filtered and washed twice with 50 ml of water of the same
temperature. 58,4 g of the product was obtained by crystallization from a boiling 30% solution of
methanol (250 ml of water, 120 ml of CH3OH), representing a yield of 85% based on the amount of o-
carborane taken.
2.2.2 Preparation of methyl o-carborane (E179)
A mixture of 50 g of B10H14, 35 ml of CH3CN, and 300 ml of benzene was refluxed in 1 l flask furnished
with a magnetic stirrer for 2 hours. A 42,5 ml portion of a 80 % toluene solution of propargyl bromide
was carefully added dropwise to the mixture. After the mixture had been refluxed for another 35 hours,
it was cooled to room temperature and solvents were evaporated under vacuum. The solid
evaporation residue was extracted three times with 100 ml of hexane and the combined hexane
extracts were agitated four times with 50 ml of 10% NaOH and with water. The yellowish hexane
solution was dried with anhydrous MgSO4 and filtered, and the hexane was evaporated under vacuum.
85 g of 1-CH2Br-1,2-C2B10H11 were obtained by distillation under vacuum from an oil bath, representing
a yield of 80 % based on the amount of B10H14 taken.
In a 1 l flask furnished with a magnetic stirrer a solution of 85 g of 1-CH2Br-1,2-C2B10H11 in 300 ml of
anhydrous diethyl ether was added to a 10 g suspension of metallic Mg. After the reaction mixture had
been refluxed for three hours, it was cooled to room temperature and poured onto crushed ice. After
the vigorous reaction had finished, 125 ml of 3 N NCl were added to the mixture. The etheric layer was
separated, dried with anhydrous MgSO4, filtered, and the ether was evaporated under vacuum. The
crude 1-CH3-1,2-C2B10H11 was dissolved in benzene and filtered through a silica gel column. The
benzene was evaporated under vacuum and the pure -CH3-1,2-C2B10H11 was dried in an oil pump. An
amount of 52 g was obtained, which represents yields of 92% and 80% with regard to the initial
amounts of 1-CH2Br-1,2-C2B10H11 and B10H14, respectively.
2.2.3 Preparation of phenyl o-carborane (E180)
A mixture of 100 g of B10H14, 70 ml of CH3CN, and 600 ml of benzene was refluxed in a 2 l flask
furnished with a magnetic stirrer over a period of 2 hours. 100 ml portion of freshly-distilled
phenylacetylene was carefully added dropwise to the mixture. After the reaction mixture was refluxed
for 48 hours, it was cooled to ambient temperature and the solvents were evaporated under vacuum.
24
O O
12`
7 8
9
10126
2`1`
3`
4`
4
5`6`
11
11`
1
5
8`
9`
Co
COSDIOX
10`
32
7`
12`
7 8
9
10126
2`1`
3`
4`
4
5`6`
11
11`
1
5
8`
9`
Co
10`
32
7`
O
O+
excess
The brown viscous evaporation residue was extracted three times with 250 ml of hexane. The
combined hexane extracts were concentrated to half volume and this solution was poured on a silica
gel column. Hexane was used as an eluent for obtaining a crude product. After the hexane was
evaporated, 102 g of 1-C6H5-1,2-C2B10H11 were obtained, representing a yield of 57% based on an
initial amount of B10H14 taken.
2.2.4 Preparation of [8-C4H8O2)(C2B9H12)2Co] (E181)
A slightly modified procedure described in literature12 is used.
Cosan (40.5g) was dissolved in dried dioxane (120ml). Then Me2SO4 was added and the reaction
mixture was heated on an oil bath at 80-90°C for 3h. After cooling down, 30% ethanol was added
(140ml) under vigorous stirring continued for 1h. Then, the precipitate was allowed to settle down
during 30min., sucked off and washed with 50% ethanol (3x 30ml). Product is dried on the air for 24h
and then in vacuum at 60°C for 8h. Yield 18,0g.
2.2.5 Preparation of 8,8'-μ(NH2)(C2B9H10)2Co (E182)
To the suspension of (C2B9H11)2Co(-)Cs(+) (4.6 g, 0.01 mol) in 50 ml of benzene and 50 ml of
concentrated H2SO4, cooled to the semo-solid slurry stage, Na NO2 (1.4 g, 0.02 mol) was added in
one portion. The mixture was stirred for 1 h at +5° C, 3 h at room temperature and left to stand
overnight. The red benzene layer was separated, poured onto a column of 200 ml of silica geland
eluted with benzene until the front reached the bottom of the column. The distinct layer at RF 0.4 was
removed mechanically, extracted with 200 ml of benzene , the extract concentrated to 50 ml, covered
carefully with a layer of 200 ml hexane and left to stand overnight. Red needles of product (1.72 g,
50.4 % yield on the COSAN) separated. Two more by-products were present in the reaction mixture
that were separated on the column as orange layers at RF = 0.06 and 0.17 (benzene).
2.2.6 Preparation of dihydroxy-Cosan (E184)
A stirred suspension of COSAN.Cs (10 g, 2.2 mmol) in 80% aqueous sulphuric acid (100 ml) was
heated in a 140°C bath with gradual dissolution of the major part of solids. The reaction was
monitored in 30 min intervals by HPLC with UV detection at 302 nm; when COSAN.Cs was no more
detectable (after 24 h), the mixture was cooled down. At this moment the product contained 94 % of
main product and 6 % of two other anions with k' values < 1.0. The mixture was diluted with water (100
ml), the conjugate acids were extracted three times with Et2O (30 ml portions). To the combined ether
25
extracts water (20 ml) was added and Et2O was stripped off. Product was easily converted to the more
convenient 3-HNMe3 salt with a slight excess salt Me3N.HCl in hot 50% aqueous EtOH. Yield was
8,55 g, 94%.
2.2.7 Preparation of [8,8'- μ–O2 P(O)Cl-(1,2-C2B9H10)-3,3'-Co]-[Me3NH]+
(E186)
To a suspension of the Et3NH+ salt of Dihydroxy-COSAN (4g, 8.7 mmol) in chloroform (30 ml), POCl3
was added (2.52 g, 16.5 mmol) and the slurry was stirred 2 h at ambient temperature. An evolution of
gaseous HCl occurred along with temporary dissolution of solids and precipitation at the end of this
period. Then triethylamine (3 ml, 20.6 mmol) was dropwise added during 20 minand the mixture was
stirred for additional 2 h during which period solids dissolved again. An addition of P(O)Cl 3 (0.8 g, 5
mmol) and 1.0 ml (6.8 mmol) of Et3N was repeated again and the reaction mixture was stirred for
additional 2 h. The reaction was quenched by a careful addition of water (50 ml) and the bi-layer
system was stirred for 2 h. During this period the main portion of the product precipitated. Solids were
filtered, washed with two portions of chloroform (10 ml) and dried; 3.12 g (78 %) of the essentially pure
product were obtained. An additional quantity (0.1 g) was obtained from the combined chloroform
extracts and washings by evaporation of the solvent and repeated recrystallization of the solid residue
from hot 60% aqueous ethanol. Overall yield of was 3.18 g, 79 %.
2.2.8 Preparation of (C6H5)2POCH2CO2-C6H4-NO2 (E188)To dried hexane (480ml) dry isopropanol was added (17.2 ml) followed with Et3N (34.2 ml)13. The
solution was cooled down on an ice bath, and then chlorodiphenylphosphine (40 ml) was added
through a septum from syringe. The reaction mixture was stirred 30 min. at the bath, then 4h at room
temperature. Then, solids were filtered off on a glass filter under argon atmosphere. The precipitate
was washed with hexane (twice 50 ml) and discarded. The solution was evaporated on the vacuum
line until a viscous liquid resulted 43,2g (79%). The flask was filled with argon and opened, and 12,4
ml of BrCH2COOEt was added in one portion. The flask was cooled at the beginning by a water bath,
and then left to worm up by an exothermic reaction. Then the content of the flask was heated at bath
worm 110oC for 1h. The flask was equipped by reflux condenser and nitrogen inlet and then 36 g of
NaOH in water-ethanol mixture 1:1 (275 ml), and was added and heated at 75 oC warm bath for three
days. After cooling down, ethanol was evaporated off and water (250 ml) was added. The solution was
extracted with chloroform (twice with 80 ml) and the chloroform extracts were discarded. The pH of the
solution was adjusted to 1 with 6M HCl and the product was extracted to CHCl 3 (three times 200ml).
Chloroform extracts were evaporated to dryness and the diphenylphosphonylacetic acid was dried in
vacuum over P2O5. Yield 41,2g.
Diphenylphosphonic acid 41.2g and p-nitrophenol 21,7g were dissolved in dry chloroform (dried over
P2O5 and distilled, 240ml) and thionyl chloride (18.6 ml) was added dropwise through septum. The
mixture was kept at 50oC (bath temperature) for 12 h under argon atmosphere. Then chloroform
(160ml) was added and washed with 0oC cold 5% solution of NaHCO3 in water in the separatory
26
funnel. Then, the chloroform layer was washed three times with water (200 ml) and the chloroform
was then evaporated and dried in vacuum. Then the crude nitrophenylester was treated with
ethylacetate (180 ml) at room temperature for 1h and then cooled down overnight. Precipitate was
filtered off and washed several times with cold ethylacetate (25 ml). Mother liquors were concentrated
and left to crystallize in the fridge giving second crop of the product. The combined crops were
recrystallized once more from ethylacetate. Overall yield 26.4 g, yellowish solid.
2.2.9 Results and conclusionKatchem Ltd. in cooperation with IIC verified the designed methods of syntheses. These new methods
were used for preparation of larger quantities of described chemicals in experimental part.
These chemicals were used as intergrades for other syntheses in frame of project research.
Exactingness of syntheses would take further optimization of reactive conditions at realization in
industrial scale.
Katchem Ltd. in close cooperation with IIC verified the laboratory methods of syntheses for potentiality
of their using in larger scale and prepared series of commercially unavailable boron clusters for further
research. Within the work on project the available analytical methods were also verified for
determination of purity grade. The achieved results corresponded to the amount of prepared
specimens.
Katchem Ltd. carried out its tasks in project and prepared series of specimens for research of the
other partners. Katchem Ltd. is ready to use existing results of project for large-scale preparation of
specimens for testing in practice.
27
2.3 MALONAMIDE AND GLYCOLAMIDE DERIVATIVES ( Universidad Autónoma De Madrid )
2.3.1 Malonamide extractantsLipophilic malonamides have been employed successfully as extractants for lanthanide and actinide
cations from strongly acidic media in aliphatic solvents (DIAMEX process)14. Many complexes between
malonamides and lanthanide/actinide cations have been studied by different techniques. It has been
observed in X-ray structures15 that two malonamide ligands participate in the complexation of different
lanthanide cations, and by other studies, that two or more ligands participate in the cation extraction 16.
Preorganization of two or three malonamide ligands into a molecular platform could both enhance the
extraction efficiency due to chelate effects and increase its selectivity through their specific
geometrical arrangement
N NC8H17
O OC8H17
Me MeOC6H13
Figure XIV. Example of malonamide ligand [DMDOMA= Dimethyldioctylmalonamide]
At the end of the last project several calix[6]arene functionalized with malonic derivatives had already
been synthesized. These products were only soluble in CH2Cl2 and no extraction was observed.
Based on these considerations, Madrid team suggested the synthesis of calix[4]arenes and
calix[6]arenes functionalized with malonamide derivatives and highly lipophilic chains on the platform
and/or the ligand.
On the other hand, studies in recent years have shown that compounds containing soft donor atoms,
such as N and S, can provide higher selectivity for Am(III) over Ln(III) (CYANEX 301)17. In order to
increase the extraction for the minor actinides, the synthesis of thiomalonamide moieties attached to
the corresponding calixarene platforms was proposed.
N NR
S SR
R RR
Figure XV. General structure of thiomalonamide ligand
The whole list of compounds synthesised by Madrid team is given in Annex 1.
2.3.2 Calix[4]arenesThe proposed calix[4]arenes were substituted either at the upper rim or at the lower rim, both of them
in either cone or 1,3-alternate conformation. In this kind of structures, it was planned to attach the
malonamide moiety through the central carbon.
28
OROO OOR
C8H17
C8H17 R
X X tButBu
OO OO
tButBu
RR
XX
OROR
XX
XX
OR O
OO
O
X
XX
X
N NOO
X =Me
C8H17
Me
C8H17
The synthesis of E67 and E65 (cone conformation) was completed following the same strategy:
N NO- O
C8H17 C8H17
Li+
DMF 70ºC
R3 R4
O O22
R1 R2
R1=R3=R4= H R2= C8H17
R1=R2=R3=R4= H
R3
O O22
R1 R2
NI
ii )MeI,DMF
i) Me2NH; CH2O THF or Dioxane
R1=R3= H R2= C8H17
R1=R2= H R3=
R3
O O22
R1 R2
OO
N
NC8H17
C8H17
R1=R3= H R2= C8H17
R1=R2= H R3=NCH2
IO O
N NMe
C8H17 C8H17
Me
The extraction experiments with already delivered compounds E67 and E65 resulted in very low
values for the distribution coefficients of Eu and Am. This lack of activity might be due to the presence
of free phenol groups. Attempts to alkylate E65 in order to fix the 1,3 alternate conformation were
performed, but the expected compound E66 could not be isolated from the other conformers.
The synthetic strategy proposed for compounds 2 and 3 relied on the reaction of calixarene bearing a
good leaving groups with the malonamide enolate.
OO OO
RR
XX
N
O O
NC8H17
C8H17
M
+
OO OO
RR
OO
NN
C8H17
C8H17
OO
N
NC8H17
C8H17
X= Br, I, OMs
R=C3H9 or (CH2)2OEt or Me
R= (CH2)2X
R=C3H9 or (CH2)2OEt or Me
R= O O
NNC8H17 C8H17
A variety of good leaving group precursors of 2 in cone conformation with two of the distal positions
functionalized with methyl, propyl or ethoxyethyl groups was prepared. Unfortunately, in neither case
the expected disubstituted compound could be detected, the starting calixarene being recovered in
most instances and only a small amount of monosubstituted compound could be isolated in the case
of a precursor with two methyl groups in distal positions.
29
R=H E67 R=H E65
3
E65
2
3
2
In the case of compound 3 several routes to alkylate it with the appropriate four carbon linker in the
1,3-conformation were attempted without apparent success (direct reaction or stepwise). Therefore, an
alkylating agent with a shorter linker, namely a two carbon chain, was used. Finally we synthesized a
precursor bearing a good leaving group, although the final reaction gave a complex mixture of partially
alkylated compounds.
Due to these unexpected negative results, it was decided to change the synthetic strategy, attaching
the linker on the malonamide moiety and leaving the calixarene alkylations for the final steps.
However, monoalkylation of malonamide enolate, deprotection of hydroxy group and introduction of a
leaving group (by bromination or mesylation) failed in all cases and only lactone 4 could be isolated.
Consequently, this approach had to be abandoned too.
N
O O
NC8H17
C8H17
i) LDA , THF TsOCH2CH2OAll
ii) Pd (C), TsOH EtOH / H2O /
N
O O
NC8H17 C8H17
OH
PPh3, CBr4,CH2Cl2
or
NMM, (Ms)2O, CH2Cl2
O
O O
NC8H17
2.3.3 Calix[6]arenesThe synthesis of the different substituted calix[6]arenes at the lower rim (E68, E70 and E72) was
completed:
t-But-Bu
O
t-Bu
O
t-Bu
OOO
t-Bu
O
t-Bu
Z
ZZ
ZZ Z
t-But-Bu
O
t-Bu
OMe
t-Bu
OO
O
t-Bu
O
t-Bu
Me MeMe
t-But-Bu
O
t-Bu
O
t-Bu
OOO
t-Bu
O
t-Bu
Me MeMe
HN NC8H17
Me
OOZ=
ZZ ZZ Z
Following a similar scheme: alkylation of the selected phenolic positions with a propylphthalimide as
linker, deprotection of amine group and acylation with the appropriate malonic acid:
t-Bu t-Bu
O Omn
R1 R2
i) NaH
Br NPhth
t-Bu t-Bu
O Omn
R2
NH2
ii ) NH2NH2HCl EtOH, HO N C8H17
O O
PyBOP or (ClCO)2
n=m=3
n=2, m=4
n=m=3
R1= H R2= Me
R1=H R2= Me
R1=R2= H
R2= Me
R2= Me
R2= NH2
R2= Me
R2= Me
R2= NH
t-Bu t-Bu
O Omn
R2
HN
N
OO
C8H17
O ON C8H17
n=m=3
n=2, m=4
n=m=3
n=m=3
n=2, m=4
n=m=3
30
E68 E72E70
E70
E68
E72
4
The malonic moieties were selected by comparison with the extraction results described for the simple
DIAMEX malonamides, but longer aliphatic chains at amide end or at central carbon gave poor
extraction efficiencies18.
Attempts to synthesize calix[6]arenes endowed with more lipophilic chains (butyl or octyl groups) over
the platform failed because of the steric hindrance on the substrate.
The synthesis of some proposed upper rim substituted calix[6]arenes was successfully achieved:
Zt-Bu
O
t-Bu
O
t-Bu
OO
O
Z
O
Z
H17C8C8H17
C8H17MeMeMe
t-BuZ
OMe
t-Bu
OMe
t-Bu
OOO
Z
O
t-Bu
Me MeMeMe
HN NC8H17
Me
OOZ=
The synthetic steps were similar in both cases; starting from the appropriated functionalized platform,
nitration at the para positions of the aromatic ring with the free phenolic positions, alkylation of these
hydroxyl groups, reduction of nitro groups to amine and acylation with the malonic derivative. In this
series, the related hexasubstituted calixarene could not be obtained due to the poor yields in the
nitration and reduction steps.
t-Bu t-Bu
O Omn
R1 R2
i) HNO3/ H2SO4 1:1
NO2 t-Bu
O Omn
R1 R2
ii ) NaH, R1X
HO N C8H17
O O
iv) PyBOP or (ClCO)2
n=m=3
n=2, m=4
R1= H R2= Me
R1=H R2= Me
R1= C8H17 R2= Me
R1=R2= Me
R1= C8H17 R2= Me
R2= Me
NH t-Bu
O Omn
R1 R2
n=m=3
n=2, m=4
n=m=3
n=2, m=4
ii ) NH2NH2HCl Pd(C), ROH,
NO
O
C8H17
These upper rim calixarenes are more rigid than the related lower rim calixarenes, and it was
proposed to use more flexible upper rim platforms in order to obtain better extraction results. The
compounds have a methylene group at the para position as spacer, but the synthesis of the
corresponding precursors was unsuccessful.
The last products have the malonamide moieties attached through an amide nitrogen. The spatial
disposition of the ligands was in the same direction than the aromatic ring but the real arrangement
around the cation is not known. In order to find the best orientation for the ligands, it was suggested to
prepare compounds 5, 6 and 7, which have the corresponding malonamides linked through the
central carbon:
31
E71 E69
E71
t-Bu
O
t-Bu
O
t-Bu
OO O
XX
MeOMeMe MeMe Me
X
O OO
OO
O
XX X
MeMeMeMe Me
Me
X XX
N NOO
X =Me
C8H17
Me
C8H17
t-But-Bu
O
t-Bu
OMe
t-Bu
OOO
t-Bu
O
t-Bu
Me MeMe
X X
The synthetic strategy for compound 5 relied on the reaction between a calixarene bearing a good
leaving group and a malonamide enolate. Owing to its low reactivity only a small percent of
monosubstituted compound could be isolated. As for calix[4]arenes E67 and E65, the first step in the
synthesis of compounds 6 and 7 was the introduction of aminomethyl groups vía a Mannich reaction
with dimethylamine and formaldehyde. The reaction failed in the case of 7 but worked well with 6,
whose synthesis was finished at the end of the project.
After the dissapointing results in the distribution coefficients for Am(III) and Eu (III) obtained with the
malonamide derivatives, Madrid team decided not to synthesize the thiomalonamides analogues.
2.3.4 Diglycolamide extractantsIn the last years several extraction studies were made with diglycolamide derivatives. The first results
obtained with compounds containing this moiety showed to be better extractants than related
malonamides and higher selectivities were observed19,20,21.
NO
OC8H17
C8H17
N
OC8H17
C8H17
Figure XVI. Example of diglycolammide ligand (TODGA= tetraoctyldiglycolamide)
Taking into account the poor extraction results obtained for the platforms with malonamides, we
proposed the synthesis of diglycolamide moieties linked to a calixarene platform. The selected
compounds were calix[4]arene-and calix[6]arene-diglycolamide conjugates attached through the
amide nitrogen.
t-But-Bu
O
t-Bu
O
t-Bu
OOO
t-Bu
O
t-Bu
Me MeMe
Z=
ZZ Z
Zt-Bu
O
t-Bu
O
t-Bu
OO
O
Z
O
Z
H17C8C8H17
C8H17MeMeMe
ZZ
OO OO
ZZ
RR
RRO
ZZ
OO
Z ZO
HNO
NH
O OC4H9
C8H17C8H17
C8H17
C8H17
32
R= C3H7 E73
R= C8H17 E74
E77
5 6 7
E75
E76
The synthetic scheme for E73, E74 and E75 consisted of; alkylation, nitration, reduction and finally
acylation with the ligand.
t-Bu
O4
R1
ii) HNO3/ H2SO4 1:1
NO2
O4
R1
i ) NaH, R1X
iv) PyBOP or EDC HCl
R1= C3H9
R1= C8H17 (cone)
R1= C8H17 (1,3-alternate)
NH
O4
R1
ii ) SnCl2, EtOH
HNO
NH
O OC4H9
OO
O HN
C4H9
E76 and E79 were synthesized with a similar protocol as for E69 and E68, respectively, but not
extraction resulted from E73, E74, E74 and E76 due to the low solubility of all these compounds in
NPHE. Probably the problem was the number of aliphatic chains of the diglycolamide moieties.
Results with tertiary amides were better than with secondary amides.
No positive results were obtained for E79, which was sent to CIEMAT for extraction determination, due
to its insolubility.
After this outcome, Madrid team proposed the same platforms with a similar diglycolamide moieties,
but with ligands bearing a tertiary amide:
t-But-Bu
O
t-Bu
OMe
t-Bu
OO
O
t-Bu
O
t-Bu
Me MeMe
ZZ
t-BuZ
OMe
t-Bu
OMe
t-Bu
OOO
Z
O
t-Bu
Me MeMeMe
t-But-Bu
O
t-Bu
O
t-Bu
OOO
t-Bu
O
t-Bu
Me MeMe
Z= ZZ Z
Zt-Bu
O
t-Bu
O
t-Bu
OO
O
Z
O
Z
H17C8C8H17
C8H17MeMeMe
HNO
N
O OC4H9
At the end of the project, the synthesis of the proposed ligands was completed and only E77 and E78 have been sent to CIEMAT for extraction experiments affording low distribution coefficients.
The contribution of the research group in Mainz consisted of the development of new ligands for
actinides and lanthanides. In coordination with the other synthetic groups, Mainz University focused on
the CMPO (carbamoylmethylphosphine oxide) group as ligating group, which was attached to various
basic skeletons alone and in combination with other functional groups. The structure of each
compounds synthesised is given in Annex 1.
2.4.1 CMPO-Functionalized Dendrimers
Following the idea, that a high local concentration of CMPO-functions would be beneficial, dendritic
polyamines of the poly(propylene imine) (PPI) and of the polyamidoamine (PAMAM) type (both up to
the 5th generation) were reacted with the known active ester AE to obtain dendritic poly-CMPOs with
up to 64 CMPO-functions on the surface (Compounds E31, E32, E33, E34 (2nd to 5th generation of
the PPI-series) and E38, E39 4th/5th generation of PAMAM). For the PPI-series also a statistical
combination of 80% to 60% of CMPO-functions with 20% to 40% acetamide groups was checked (E35
– E36).
The solubility of these dendrimers in water limits their use in liquid/liquid extraction, but suggests their
application in homogeneous aqueous phase, where a separation by membrane filtration is possible for
polymeric ligands. (A patent was filed by CEA Cadarache22).
It could be shown, that also highly branched polyglycerols could be converted into polyamines by
reaction with N-bromo-propylphthalimide followed by hydrazinolysis (E37). Thus a cheaper starting
material for the synthesis of poly-CMPOs is available.
2.4.2 Dendritic Octa-CMPO-Calix[4]arenes
Calix[4]arene derivatives in the cone conformation with eight CMPO-functions attached to the narrow
rim (E41, E42) or to the wide rim (two types, E43, E48) were also prepared (see Scheme 1 in Annex
2). Their extraction behavior is poor in comparison to wide or narrow rim tetra-CMPOs. NMR-relaxivity
studies (see 3.5 p: 72) which suggest the formation of oligomeric species for the wide rim tetra-CMPO
revealed a 1:2 complex (ligand to metal) for a wide rim octa-CMPO (E44) with Gd(III).23
If only two phenolic OH-groups are used to attach four CMPO-functions (like in E40) the other two OH-
groups may be used in principle for the attachement of further functions.
2.4.3 Tetra-CMPOs, Functionalized for Covalent Attachment
In order to attach wide rim tetra-CMPOs to the surface of (magnetic) particles aminoalkyl ether
derivatives were synthesized bearing one, two or four aminoalkyl ether groups (of different length) on
the narrow rim. The synthetic sequence (for an example see Scheme 2 in Annex 2) starts with the
preparation of (propyl/ω-phthalimidoalkyl) ethers of t-butylcalix[4]arene in the cone-conformtion,
followed by ipso-nitration, reduction of the nitrogroups, acylation by the active ester AE and
34
deprotection of the amino-function on the narrow rim (compounds: E152, one aminopentyl arm; E149,
E150, E151, two aminoalkyl arms of different length; E154, four aminopropyl arms). Analogues
consisting of a single phenolic unit were also synthesized as models (compounds E144, E145).
Covalent attachment to the particle surface was achieved by reaction with cyanyrchloride functions
linked to the particles before (see 3.3 p: 60) and led to a complete covering of the available surface.
Extraction studies (see 3.1 p:45) revealed the advantage of the preorganisation of CMPO-functions on
the calixarene platform prior to the fixation to the particle surface.
Further amino-CMPOs for attachement: E143 and E147.
2.4.4 N-Methyl CMPO-Calix[4]arenes
N-Methyl analogues of the wide rim tetra-CMPO calix[4]arenes (E10, E11) were prepared for the first
time as examples for tertiary amides. Starting with a tetramino tetraether in the cone-conformation
acylation with BOC-anhydride, N-alkylation with MeI and deprotection led to the tetra-methylamino
substituted calix[4]arene (other strategies to synthesize such secondary amines failed) which was
finally acylated by the active ester AE (see Scheme 3 in Annex 2). These tertiary CMPOs show a
lower, but still interesting extraction ability, but seem to be more stable during long time contact with
nitric acid. Surprisingly they form even larger oligomeric assemblies (inspite of the absence of
hydrogen bonding NH-groups) with lanthanide ions than the NH-compounds, as shown by relaxivity
studies and by light scattering (see 3.5 p: 72).24
Attempted N-methylation of a wide rim tetra-CMPO lead to the completely N,C-alkylated compound
E12, which did not show remarkable extraction properties.
2.4.5 CMPO-Compounds for Stability Studies
Two wide rim tetra-CMPOs (the NH and N-Me derivatives E9 and E10 respectively) and a narrow rim
tetra-CMPO (MZ37) were resynthesized in larger quantities. Their stability towards nitric acid and
irradiation was studied in detail by CIEMAT (Madrid). Model compounds for the repeating phenolic
unit (MZ34, MZ41 and MZ38), as well as a dimer (MZ35) and a trimer (MZ36) of the wide rim NH-
CMPO series were also prepared. They should lead to an understanding of the structural changes
which might occur under working conditions (irradiation, contact with nitric acid) and consequently to
an improved design of ligands.
2.4.6 Calixarenes with Mixed Ligating Functions
Various calix[4]arenes in the cone conformation, bearing CMPO-functions in combination with other
ligating functions on the wide (E122, E123, E124) or narrow rim (E128, E132, E125, E126, E133,
E127) have been prepared. Among them the combination CMPO/picolylamide (E129, E131) should be
especially mentioned which were explored in close collaboration with Parma.
Up to now the most remarkable result is a high Am over Eu selectivity (in extractions from strong nitric
acid) found accidentally for a wide rim tri-CMPO-mono-acetamide (E122, E121). Its synthesis (see
35
Scheme 4 in Annex 2) may serve as an example how the wide rim derivatives are obtained, using
BOC-protection of amino groups. (Analogous compounds with alternating order of two ligating
functions on the wide rim are not available in this way, and an improved synthesis of a dinitro-diamino
derivative was developed25.) The synthesis of derivatives with different ligating functions on the narrow
rim is illustrated by the example of Scheme 5 in Annex 2.
Wide rim mono- and tri-CMPO derivatives (E13, E14), synthesized and studied to complete a whole
series of these compounds should be mentioned here also.26 The combination of CMPO-functions with
cosan residues (collaboration with Rez) must be also seen in this connection and NH2/CMPO-
derivatives (E120, MZ55) were checked for the attachement of cosan (Rez).
2.4.7 CMPO-Calix[4]arenes in the 1,3-Alternate Conformation
Mainz University have started also to explore the calix[4]arene skeleton fixed in the 1,3-alternate
conformation as a platform, to which four CMPO-groups or two CMPO-groups in combination with two
other ligating functions may be attached. To point in the same direction two of these groups have to be
fixed at the wide and two on the narrow rim (using spacers of different length). The synthetic strategy
is demonstrated in Scheme 6 in Annex 2, in which the O-alkylation of the nitrophenol units is the
crucial step. To obtain the 1,3-alternate conformation (cone and partial cone are always formed as
side products) Cs2CO3 must be used, while the low nucleophilicity of the nitrophenolate requires the
reactive allylbromide. Reduction of the allylether and the nitro groups can be achieved in one
subsequent step.
The platform of the 1,3-alternate calix[4]arene can be used also to attach other ligating functions as
amides, and also combinations of functional groups.
2.4.8 Octa-CMPO-Calix[4]arenes
As mentioned above, conformational isomers may be obtained as side product especially during the
formation of tetraethers in the 1,3-alternate conference. As an extension of its programme, Mainz
University thus decided to attach eight CMPO-groups to a calix[4]arene skeleton fixed in the four basic
conformations. Four of these groups are directly bound to the wide rim and four via a C 3-spacer to the
narrow rim. From the four conformational isomers possible for these octa-CMPO-compounds (see
Scheme 7 in Annex 2) the cone and partial cone derivative are presently under purification.
Surprisingly, the 1,2-alternate derivative (E20) shows an interesting selectivity within the lanthanide
series (results from Strasbourg see:3.2 p:54), and this conformation probably should be realized also
for tetra-CMPO derivatives.
36
2.5 EXTRACTANTS BASED ON HARD AND SOFT DONOR GROUPS ( P arma University )
The structure of the compounds synthesised by the Parma group is given in Annex 1.
2.5.1 Synthesis of calixarene bearing picolinamide binding groupsThere are quite few works in the literature on the use of alkyl picolinamides1;2 for the selective
separation of actinides from lanthanide, however, it is reported that, in some cases, they can give rise
to a promising An/Ln selectivity.1 In this project, Parma team explored whether the introduction of
several picolinamide moieties on the calixarene macrocycle backbones could result in a cooperative
action of these binding groups, thus increasing the efficiency and selectivity in the binding of actinide
ions from acidic radioactive waste.
It was therefore studied the best way to form the amide bond of picolinamides by using different
strategies. All of these strategies require, however, the reaction of an amine with an activated picolinic
acid. Different types of activation were required such as acyl chloride, pentafluorophenyl active ester
or in situ use of coupling reagents such as HBTU or HATU.
The results show that picolinic acid chloride give good yields on simple alkyl amines, but when
calixarene ethers are used, it also brings to a considerable amount of ether cleavage which a
significant decrease of the acylation yield. Therefore it was establish that the best way to acylate
amine derivatives of calixarene ethers is to use the pentafluorophenyl ester of picolinic acid. 3 In order
to study the cooperative effect of different binding groups on a single calixarene scaffold it was also
synthesised the monomeric N-butyl picolinamide (E50) from butylamine and the chloride of picolinic
acid.
On the other hand, several calix[n]arene ligands (n = 4, 6, 8) having picolinamide at the upper or lower
rim and different conformational properties were synthesised by reacting the calixarene amines with
pentafluorophenyl active ester of picolinic acid in dry dichloromethane (DCM). Therefore,
calix[4]arenes bearing 4 picolinamides at the lower rim and in the cone conformation (E52, E53 and
E54) were prepared. They differ for the length of the spacer between the calix and the binding group
or for the substituent at the upper rim.
Three calix[6]arene (E57, E58, E59) bearing 6 picolinamides and two calix[8]arenes (E60 and E61)
having 8 binding groups were also prepared. E59 and E61 bear tert-butyl and benzyloxy groups in
para position, respectively. Most of them are conformationally mobile in solution while E59, because of
the presence of the bulky alkyl groups at the upper rim, is present in a mixture of conformation in
DMSO solution slowly interconverting on the NMR time-scale. The main conformer present is the
1,2,3-alternate, which has three adjacent phenolic nuclei pointing up and three down. Also E58,
analogous to E59 but with no t-butyls at the upper rim and therefore conformationally mobile in
solution, in the solid state shows this 1,2,3-alternate structure as depicted from X-ray diffraction
studies on a single crystal.
Calix[4]arene E55 and E56 having 4 picolinamides linked to the amide N atom directly or through a
methylene spacer at the upper rim were also prepared.
37
As a preliminary check of the potentiality to have terpyridine groups on a calixarene scaffold for the
selective extraction of actinides, Parma team has also synthesised a calix[4]arene (E87) fixed in the
cone conformation and bearing 4 terpyridines at the lower rim. An easy way to introduce terpyridines
on a calixarene scaffold was achieved by reacting the tetra(4-bromobutyloxy)-p-tert-butylcalix[4]arene
with a terpyridine, the (2,6-bis(pyridin-2-yl)-4-hydroxy-pyridine, having an OH group in para position of
the central pyridine nucleus.
2.5.2 Synthesis of calixarenes bearing both hard and soft donors groupsIt is commonly accepted that the use of donor atoms softer than oxygen, especially N and S can afford
a higher selectivity for similarly sized actinides over lanthanides. However, these softer donor atoms
often give rise to less stable complexes. In order to find a good compromise between efficiency and
selectivity, the possibility to introduce on the calixarene scaffold both soft and hard donor atoms was
explored.
Therefore were synthesised calix[4]arenes having, besides the picolinamide binding groups, also
harder groups such as acetamide or iminodiacetic moieties. E134 bears two picolinamide and two
acetamide groups in distal (1,3) positions at the lower rim of p-tert-butylcalix[4]arene. E135 has the
same structure but the Oxygen atoms of the carbonyl groups of acetamide and picolinamide are
substituted with Sulphur atoms.
Another approach to have ligand with mixed hard and soft donor groups consists in the insertion on
the calix[4]arene scaffold of iminodiacetic units through a multistep synthesis4. Compounds E136 bears two picolinamide groups close to two iminodiacetic units. The latter binding groups are usually
quite efficient in the complexation of di- and trivalent cations and have widely been used in
coordination chemistry of lanthanide ions.5 Another calixarene ligand which possesses two
iminodiacetic units is E137 which also bears two CMPO binding groups in distal (1,3) positions.
2.5.3 synthesis of calixarenes and CTVs bearing 3 or 4 thenoyl trifluoroacetone (TTFA) or CMPO moieties
It is well established from literature data that thenoyltrifluoroacetone [4,4,4-trifluoro-1-(2-thienyl)-1,3-
butanedione] forms 3:1 complexes with actinides and lanthanides, acting as a beta-diketone chelating
agent, and that it can be used as reagent for their determination. It was therefore evaluated the
possibility to insert this binding site, through its heterocycle side, onto pre-formed macrocyclic
platforms.
Because of the lack of literature data on functionalization reaction of this type of heterocycle, a
preliminary study on the electrophilic aromatic substitution of the commercially available
thenoyltrifluoroacetone was carried out. It was found that chlorosulfonation reaction can be carried our
in a regio-controlled manner by the careful choice of reaction condition and ratio between reagents. In
particular, it was verified that the direct chlorosulfonation of thenoyltrifuoroacetone with neat
chlorosulfuric acid gave 33% overall yield of chlorosulfonated compound that was directly reacted with
p-octyloxyaniline to give the corresponding sulfonamide. However, a detailed structural analysis of this
product showed the presence of two isomers identified as the 5-(4,4,4-trifluoro-3-oxobutyl)-thiophene-
38
2-sulfonic acid-(4-octyloxyphenyl)amide and 5-(4,4,4-trifluoro-3-oxobutyl)-thiophene-3-sulfonic acid-
(4-octyloxyphenyl)amide in 75/25 ratio respectively. The mixture of these two isomers was sent for
extraction experiments as E88. On the other hand, as confirmed also by X-ray analysis (see Figure
XVII), the reaction of thenoyltrifluoroacetone with 5 equivalents of chlorosulfonic acid in
dichloromethane at room temperature, followed by reaction with 4-octyloxyaniline, gave exclusively the
5-(4,4,4-trifluoro-3-oxobutyl)-thiophene-2-sulfonic acid-(4-octyloxyphenyl)amide isomer in 45% yield.6
Extraction experiments showed that E88 is quite efficient, although not selective in the extraction of Eu
and Am ions.
a) b)
Figure XVII. a) X-Ray crystal structure of compound E58; b) X-Ray crystal structure of
This hypothesis is confirmed by using different ”generation” dendrimers and hence of size, distribution
coefficients are independent of the dendrimer size and also of cation concentration (experiments of
filtration series).
3.1.1.3 Operating conditions for solid-liquid extraction tests
Magnetic and non-magnetic microparticles with selective chelators for radionuclides on the surface
have been tested for the selective removal of radionuclides in solid-liquid extraction system as
alternative procedure to the liquid-liquid extraction systems.
After magnetic separation of the radioactive particles the radionuclides can be back extracted. Thus
the chelator containing particles can be re-used in the extraction process.
47
For complexation experiments, a known mass of functionalised magnetic beads was put in the
aqueous phase containing actinides. After magnetic separation, the filtrate was recovered and
analysed.
The beads could, then, be put in fresh water for back extraction so that they could be re-used in the
extraction process.
Distribution coefficients (Kd) were determined from the following relation:
Equation 2
Where :
Cin : Initial concentration (or activity) of nuclides.
Cfin : Initial concentration (or activity) of nuclides.
V : Volume of aqueous phase (ml)
Mext : Mass of beads (g)
Kd: distribution coefficient (ml/g)
3.1.2 Results and discussion on screening testsResults concerning most of the extractant except beads and cosan derivatives are summarized in
Annex 3. Extraction results on magnetic particle are given in §3.3p: 60, those on cosan derivatives in
§3.4 p:67 and those on pyrazolone in §3.5 p:72.
3.1.2.1 CMPO derivatives
In previous contract, it was established that CMPO could be a promising moiety for selective
separation of actinides from lanthanides. Hence, this way of investigation was continued with several
goals like improvement of:
The extraction behaviour
The stability of the molecules towards hydrolysis and hydrolysis
The yields of synthesis in the scope of high scale production of the extractant
For starting point of this contract, a CMPO monomer (E1) was tested to remind the potentialities of this
molecule. Indeed, it shows an interesting extraction ability in NPHE among the whole range of pH, with
a slightly constant selectivity of about 2.
Different conformation of calix[4]arenes bearing CMPO moieties were studied in order to determine
the most efficient structure.
Narrow rim substituted calix[4]arenes were studied and at first, a narrow rim tetra CMPO calix[4]arene
was tested (E3). An extraction ability similar to the CMPO monomer (E1) was obtained. The effect of
the length of the spacers as well as the presence of different spacer lengths were studied in ECPM
(see §3.2 p:54). It seems that an optimum for (CH2)4 spacer is obtained. Nevertheless, the distribution
48
coefficients obtained for the narrow rim substituted compounds are quite low (about 2 for Eu3+ and 4
for Am3+).
Wide rim substituted calix[4]arenes bearing different number of CMPOs (E9, E13, E14) were studied.
It appears that tetraCMPO calix[4]arene is most efficient than compounds bearing less CMPO.
In order to understand the role of the NH groups on the extraction properties of N-CMPO-calixarenes,
N-methylated compound E10 was also synthesised. Extraction ability of the compounds decreases
drastically compare to the one of E9 with NH group, but selectivity is still interesting.
In contrast to calixarenes bearing CMPO on the narrow rim, those bearing on the wide rim such as
CMPO functions are not stable when they are put in contact with concentrated nitric acid for a long
time. After two weeks, E9 distribution coefficients decrease tenfold when in contact with HNO3 3M. On
the other hand, no decrease of distribution coefficients is observed for E10 after 22 days of contact of
this compound with nitric acid 3M (table 3).
Table 3 : Stability studies on E10
E10
(10-3M)
Nitric acid concentration : 3M
Days 1 2 3 4 5 8 15 22
DEu 0,146 0,143 0,148 0,141 0,140 0,133 0,144 0,146
Hence, N-methylated compound is very interesting because of its stability but shows a drastic
decrease of its extraction ability compared to N-CMPO-calixarenes. Other tests were also done on
methylated CMPO calix[4]arene (E12), which presents a very poor extraction ability.
In order to exploit the possibility of calixarene to adopt other conformation, 1,3 alternate CMPO
calixarene in cone conformation was tested. But, the distribution coefficient and selectivity of this kind
of compound are much lower than tetra CMPO calixarene substituted on the wide rim.
Larger cages were also tested like calix[6],[8]arenes bearing CMPOs either on the narrow (E23, E24,
E26) or the wide (E25) rim. Functionalised calix[8]arene had a poor solubility and a third phase
appeared during extraction experiments.
Among functionalised calix[6]arene, E23 (narrow rim hexa CMPO calixarene) seems to be the most
promising one with high very distribution coefficients, especially at high acidities, and also a interesting
selectivity between Am and Eu. E23 is surely one of the best efficient compound of this contract.
Hence, it was sent to CIEMAT for stability tests. Unfortunately, not enough product was available to
test it under simulated outlets from PUREX process.
Tetra CMPO cavitands were studied. In general, distribution coefficients obtained are in the same
order of magnitude than the one of tetra CMPO calix[4]arene and very lower than the ones of the hexa
CMPO calix[6]arene (E23). The selectivity of functionalised cavitand is a little bit higher than the one of
tetra CMPO calix[4]arene. Attempts on extending the chain length between the moieties and the
cavitand were not successful as a third phase appeared during extraction tests.
49
To improve distribution coefficient, Br Cosan or LiNO3 were added either in the organic phase or in the
aqueous phase. Br Cosan enhances the extraction ability of the extractants at low pH (from pH 3 to 1)
but has no effect on the selectivity. Concerning LiNO3, no effect was observed.
3.1.2.2 Dendrimers
Different generation of dendrimers (polypropylenimine) containing CMPO were synthesised (E31; E33,
E34). Distribution coefficients were found to be independent of the dendrimer size and and also of
cation concentration. Due to the positive results obtained with CMPO-dendrimers, magnetic and non-
magnetic silica particles coated with dendritic CMPO structures were prepared at Micromod.
Dendrimer with mixed CMPO and acetamide moieties were tested but selectivities were lower that the
ones with CMPO dendrimers.
A series of CMPO Polyamidoamine (PAMAM), corresponding to E38 and E39 were tested under
acidic conditions ([HNO3] 3M) and filtered using a 0.22 m filter. A sufficient efficiency is observed but
a poor selectivity is obtained compared to the one obtained with CMPO Poly(propylenimine) (PPI).
Mainz University has also synthesised a highly branched CMPO polyglycerols (E37), which is a
polymeric product with a narrow molecular weight distribution. The advantage of this compound is its
good solubility in aqueous phase. The selectivity of this compound is in the same order of magnitude
of selectivities obtained with CMPO PPI.
Due to interesting results obtained on CMPO PPI, it was decided to combine this type of compound
with a calix[4]arene structure (E40, E41, E42, E43, E44). Except E40 (di CMPO dendrimer
calix[4]arene), the other structures lead to formation of a third phase during extraction experiments.
E40 had a poor extraction ability even if selectivities are in the same order of magnitude than
tetraCMPO calix[4]arene.
3.1.2.3 CMP derivatives
CMP cavitands were synthesized in Twente but for all the compounds tested except E46 (N-
propylated CMPO cavitand), a third phase preventing from the separation of phases, appears.
Unfortunately, E46, for which extraction tests were possible, presents no selectivity Am/Eu. Third
phase or precipitation was also observed with a tetra CMPO calix[4]arene (wide rim), synthesized by
Mainz University (E49).
One attempt on tripodal CMP was also done. This compound was poorly soluble and third phase
appears during extraction tests. But, as far as the mass balance was respected, this compound seems
interesting as it presents a very poor affinity for Eu and quite good one for Am. Nevertheless, the third
phase is a problem for an industrial use of an extractant and effort should be done to keep the
extraction characteristics of this compounds, while improving its structure to minimize third phase
appearance. Anyway, this compound was sent to CIEMAT for stability tests.
3.1.2.4 Picolinamide and picolinthioamide derivatives
Tests on picolinamide monomer (E50) showed that this kind of moieties are very sensible to the pH of
the aqueous phase. Indeed, no extraction efficiency were observed at high pH.
50
In general, tests were done on the picolinamide and picolinthioamide derivatives under different
conditions (presence of LiNO3 in the aqueous phase, presence of BrCosan in the organic phase…).
Hence, it was proved that the presence of LiNO3 in the aqueous phase reduces drastically the
extraction ability of the ligand. On the contrary, adding BrCosan in the organic phase enhances the
efficiency of the extraction at low pH but has no effect on the selectivities.
One tripodal picolinamide was synthesized by Twente but presented no extraction ability among the
whole range of pH.
Different structure of calix[n]arene bearing picolinamide either on the wide or the narrow rim were
synthesized by Parma group. In general, a very high selectivity (about 12) but low distribution
coefficient is observed at low pH. Hence, adding BrCosan in the organic phase is necessary to permit
an efficient extraction.
For calix[4]arene substituted with tetra picolinamide, better extraction ability is obtained when moieties
are fixed on the wide rim. In general, increasing the chain length between the ligand and the
calixarene seems to reduce the selectivity but enhances the distribution coefficients.
For narrow rim substituted compounds (E53,E54), adding an tertianary alkyl chain on the wide rim
increases the distribution coefficients obtained.
For calix[6]arene substituted on the narrow rim, increasing the chain length between the ligand and the
calixarene tends to reduce the selectivity and the distribution coefficients. Adding a tertianary alkyl
chain on the wide rim increases the distribution coefficient but lowers drastically the selectivity.
Comparing narrow rim substituted derivatives (E57, E52, E60), it appears that better results are
obtained with narrow rim hexa CMPO calix[6]arene or octa CMPO calix[8]arene.
Less interesting results were obtained with octa CMPO calixarene bearing benzyloxy group in para
position or cavitand.
Attempts on picolinthioamide derivatives were not conclusive as no selectivity is obtained.
3.1.2.5 Malonamides and glycolamide moieties
Different structures of calix[4], [6]arenes bearing malonamides moieties synthesized by the Madrid
team (E65,E66,E67,E68,E69,E70,E71,E72). In general, the compounds had a poor affinity for Eu and
Am. Furthermore, the selectivity observed SAm/Eu (when possible) is lower than 1, which is not in the
good way for an Am removal.
Considering the disappointing results on malonamides derivatives, Madrid University change of way of
investigation and synthesized glycolamide derivatives (E73,E74,E75,E76). Unfortunately, for
compounds enabling extraction tests without third phase appearance, distribution coefficients were
very low and selectivities were poor.
3.1.2.6 TTFA derivatives
Parma university focused also on TTFA derivatives and had synthesized different structures of
calix[n]arene (n from 3 to 6). Good distribution coefficients were obtained with TTFA monomer at low
51
pH with a selectivity of about 2. Rigidified calix[4]arene (E92) as well as wide rim tri TTFA calix[6]arene
lead to third phase appearance during extraction tests.
Narrow rim tetra TTFA calix[4]arene shows no extraction ability along the whole range of pH, whereas
wide rim tetra TTFA calix[4]arene, wide rim tri TTFA calix[6]arene and tri TTFA CTV show high
distribution coefficients (selectivity could not be measured) at low acidity only. Nevertheless, for the
compounds with extraction ability, selectivity observed is below 1, which is a problem for extracting
selectively Am (or light actinides) from Eu (or most generally Lanthanides).
3.1.2.7 N-acylurea and N-acylthiourea derivatives
Concerning the N-acylurea binding groups, the extraction ability of the compounds synthesised by
Twente university is very low, except when BrCo is added in the organic phase. In general, selectivity
could not be estimated for most of these compounds and when it was, a slight selectivity is observed
(about 1.5).
Compounds containing N-acylthiourea binding groups (E95, E102 and the former E103 and E105)
show poor extraction ability except when BrCo is added in the organic phase. In this case, a slight
selectivity is obtained at low acidity (pH 3 and 2).
Tripodal derivatives were also synthesised but no extraction ability was observed for all of the
compounds tested.
3.1.2.8 Mixed ligating sites derivatives
During this contract, combination of different ligands presenting either good extraction ability and/or
good selectivities was fixed on calix[4]arene.
Hence, mixed CMPO-acetamide derivatives were synthesized by Mainz University.
For wide rim substituted derivatives, the influence of the number of each ligand as well as the effect of
the amido group structure was studied. The structure of the amino group tested does not seem to
have an influence on the extraction results. The best extraction results were obtained for tri CMPO-
monoacetamide calixarene, with high distribution coefficient and a very good selectivity (about 12 at
high acidity). Tests on simultated outlets from PUREX process were done using E122 (see Annex 3)
For narrow rim substituted calixarene, lower extraction ability is observed. The chain length between
the ligands and the calixarene does not have an effect on the extraction properties of the molecules.
Mixed CMPO-picolinamide as well as mixed CMPO-picolinthioamide calix[4]arenes were also
synthesized by Mainz university, in order to combine the interesting extraction ability of CMPO and the
selectivity of picolinamide. Unfortunately, the extraction results were not conclusive and in the most
favorable case, only a selectivity of 2 is observed with low distribution coefficient (about 2 for Eu).
Parma university combined both hard and soft donor groups on calix[4]arene but no good extraction
results were obtained on the compounds tested.
52
3.1.3 Conclusion on promising compoundsDuring the contract, almost compounds were synthesized for extraction tests. 99 (not considering the
magnetic particle from Micromod) of them were tested in cadarache. Among all these compounds, 3
could be highlighted as they present interesting extraction ability with high selectivities:
E122 or E121. This compound presents a good affinity for Am and selectivities up to 10-12 at
high acidity. MZ8 was tested on simulated outlets from PUREX process
E23: This compound has good extraction but should be slightly less efficient than E122 as
E23 has a higher affinity for Eu.
E48. This compound is particularly interesting as it presents a very low affinity for Eu. But, the
major problem is the formation of a third phase during extraction and its low solubility in
NPHE. Hence, this compound could not be used easily for liquid-liquid extraction process and
must be improved.
These 3 compounds were sent to CIEMAT for stability tests. Among them, E122 appears to be the
most promising and it was decided to test it on simulated outlets from PUREX process (see paragraph
3.1.4). E23 and E48 could not be tested as there was not enough amount available (a few mg) to
perform the tests on simulated outlets, which required about 1g of extractants.
3.1.4 Additional works on promising compoundsCurrently the best promising compound is E122, which is a triCMPO mono acetamide calix[4]arene.
Good extraction ability and selectivities of about 10 (Am over Eu) were observed. Hence, this
compound was tested on simulated outlets coming from the PUREX process.
The simulated effluent differs from the real one by the concentration of Pr, Ru, Zr because of
experimental dilution errors and by the concentration of Am and Cm because of the limit of activity
which can be manipulated in the laboratory.
Extraction experiments were performed using equal volumes of organic and aqueous phases and a
concentration of E122 about 10-3M, which corresponds to the limit of solubility of E122 in NPHE. It
appears that no extraction could be measured (see Annex 3). The most likely explanation is that the
solubility of E122 is too low comparing to the sum of concentration of species which could be extracted
Additional experiment was performed under different conditions to increase the amount of E122. The
distribution coefficients of Am, Eu and Cm were increased but this is not sufficient for an industrial use
of E122 as extractant.
Hence, it appears important that effort should be done on synthesizing an extractant having:
- A good solubility
- A good extraction ability
- A good stability towards hydrolysis and radiolysis
- A possible high scale synthesis
Regarding all these constraints, the synthesis of a tri N-methylated CMPO- monoacetamide
calix[4]arene with long alkyl chain in para position was discussed with Mainz university. But, this
molecule could not be synthesized easily and instead of it, E121 was proposed. Unfortunately, E121 was not more soluble than E122 either in NPHE or TBP.
53
3.2 COMPLEXATION STUDIES (ECPM) During this contract, the contribution of ECPM-Strasbourg was to acquire basic knowledge on the
coordination properties in solution of the new ligands synthesized towards lanthanides, after selection
by CEA Cadarache of the most promising ones for the purpose of the contract. The three lanthanides
La3+, Eu3+ and Yb3+ were chosen as representative cations of the series and could also be considered
as models for trivalent actinides. Some data have been collected also for the actinide Th 4+. Three main
classes of ligands were investigated. They derived from calix[4]arenes (or resorcinarenes) substituted
with functional groups known for their binding abilities for these cations: acyl(thio)pyrazolones,
carbamoylmethylphosphine oxides, picolinamides
3.2.1 Experimental Two main approaches were used: liquid-liquid extraction experiments and stability constant
determination in a single medium.
3.2.1.1 Lanthanide and thorium nitrate extraction
The conditions of a standard experiment were the following: the aqueous phase consisted of solutions
of lanthanide or thorium nitrates (10-4M) in 1M HNO3; the organic phase was a solution of calixarene in
dichloromethane. 1 ml of each phase was stirred in a stoppered tube at 20°C during 12 hours. After
separation of the two phases, the concentration of the cation remaining in the aqueous phase was
monitored spectrophotometrically using Arsenazo(III) (2,2’-[1,8-dihydroxy-3,6-disulpho-2,7-
naphtalenebis(azo)]-dibenzenearsenic acid) as coloured reagent. 5 ml of a 6 10-4M arsenazo
solution were added to a 0.65 ml aliquot of the aqueous phase and the volume was finally adjusted to
50 ml with a sodium formiate-formic acid buffer (pH 2.80). The absorbances A were then determined
at 665 nm for thorium and 655 nm for the lanthanides. Since the concentration of arsenazo (III) is at
least 30 times higher than the concentration of the cation, complete complexation of the cation can be
assumed. The extraction percentage was derived from equation below:
% E = 100[1-(A-A°)/(A1-A°)] Equation 3
where A° is the absorbance of the arsenazo solution without the cation and A1 the absorbance of
arsenazo solution containing a known concentration of cation.
In order to characterize the extracted complex, the dependence of the distribution coefficient D of a
cation between the two phases upon the calixarene concentration has been examined. If the general
equilibrium is assumed to be :
Equation 4
With the overlined species referring to species in the organic phase, the overall extraction equilibrium
constant is expressed as :
54
Equation 5
Introducing the distribution coefficient D = %E/(100 - %E):
Equation 6
one obtains :
log D = log Kex[NO-3]x + n log Equation 7
With these assumptions, a plot of a log D vs. Log should be linear and its slope equal to the
number n of ligand molecules per cation in the extracted species.
3.2.1.2 Stability constant determination
The stability constants of the complexes are the best physicochemical characteristics representative of
the intrinsic affinity of a ligand for a cation in a given medium. They enable the comparison of the
different ligands betwen them, without any interference of their lipophilicity differences, as well as the
comparison with other more classical macrocycles such as cryptands and crown-ethers. The stability
constants xy of the complexes, expressed as concentration ratios [MxLy]/[M]x[L]y, refer to the general
complexation equilibrium :
xMm+ + yL MxLyxm+ Equation 8
with Mm+ = metal ion, L = neutral ligand. They were determined in methanol, at 25°C and constant ionic
strength 0.05 M in Et4NNO3 or Et4NCl, by UV spectrophotometry. The values given in the various
tables (Annex 4) correspond to the arithmetic means of at least three independent determinations.
When the ligand presented an acid base behaviour, pH-metric measurements were performed.
Direct spectrophotometry.
Upon complexation, the UV spectrum of the ligand very often undergoes small changes, from 250 to
300 nm, which in most cases, are sufficient to allow a multiwavelength treatment of the data by
computer programs like Sirko41 or Specfit42.
pH-metry
The complexing properties of ligands with acid-base properties are pH dependent and were followed
in methanol using a competition between the proton and the metal ion. Acidic solutions of the ligand in
the presence of various amounts of the metal ions were titrated by a strong base (Et4NOH). The pH
lowering with respect to the titrations curves of the ligand alone is indicative of the extent of
complexation. The protonation constants of the ligands, necessary for the interpretation of the data by
the program Sirko, were determined in a first step from the titration curves of the ligands alone.
3.2.2 Calix[4]arene tetraacyl-pyrazolonesOne calix[4]acylpyrazolone (E82) and one calix[4]acylthiopyrazolone (E84) as well as their
corresponding subunits E80 and E83 have been studied.
55
The values of the four pKa of E82 determined in methanol by pH-metry in presence of Et4NClO4 10-2M
are the following : pKa1 = 5.0, pKa2 = 6.2, pKa3 = 7.6 and pKa4 = 9.1. They show the rather strong acidic
character of this ligand. For comparison, the pKa values of the related tetracarboxylic calix[4]arene
derivative were previously found to be higher : pKa1 = 8.25, pKa2 = 9.19, pKa3 = 10.89 and pKa4
=13.39.43 The pKa of the subunit E80 was found to be pKa = 7.27 in the same medium, thus less acidic
than the corresponding calixarene E82. Complexation of the three lanthanides has also been followed by pH-metry. The titration curves
exhibiting significant drop in pH in presence of metal indicated strong complexation and were
interpreted by the formation of the mononuclear complexes LnL- and the corresponding neutral
protonated complexes LnLH. The stability constants are annexed in Annex 4 :Table 1. Actually
compound E82 revealed to contain a certain amount of Na+ cations, which were shown to have an
important role in the formation of the ytterbium complex (see the contribution of Liege University).
Further experiments are planned to investigate the behaviour of the sodium free ligand which has
been obtained since.
Formation of two complexes of 1:2 and 1:3 stoichiometries was observed with the subunit E80. In
contrast to the corresponding calixarene which forms 1:1 complexes of similar stability with the three
cations, E80 forms La3+ complexes which are much less stable than the europium and ytterbium
complexes.
The instability of solutions of the acylthiopyrazolone derivative E84 and its subunit E83, alone or in
presence of lanthanides, prevented any study of these sulphur containing ligands.
3.2.3 Phosphorylated calixarenes and related moleculesAn important part of the work has been performed on phosphorylated calixarenes bearing CMPO
units. With wide rim CMPO calixarenes the following points have been examined : (i) the effect of the
anion on the nature and stability of the lanthanide complexes formed in methanol; (ii) the effect of the
N-methylation of the CMPO residues attached to the calixarene; (iii) the influence of the number of
CMPO arms on the calixarene. Narrow rim CMPO calixarenes with (CH2)n spacers of same
(“symmetrical”) or different (“mixed calixarenes”) lengths have been studied in order to find the optimal
combination of chain lengths leading to the best complexing and extracting properties. Mixed
wide/narrow rim CMPO substituted calix[4]arenes have been studied where the calixarene
conformation is 1,3- or 1,2-alternate.
3.2.3.1 Wide rim CMPO calix[4]arenes
Anion effect on the complexation .
The extraction and complexation properties of the two upper rim CMPO calix[4]arenes (E15,E16),
equivalent of E9 but bearing respectively C3H7 and CH3 substituents at the narrow rim, have been
studied in the previous contract. The results showed a rather high level of extraction, the propoxy
derivative being better than the methoxy one, with, however, a decrease of the efficiency of both
ligands along the series, from La3+ to Eu3+ and Yb3+. The complexation results obtained in methanol,
mainly from competitive spectrophotometric measurements confirmed the strong binding of these
56
cations by this ligand but, in contrast with extraction results, did not show any significant selectivity
along the series. The complexation properties have been re-investigated in the aim of (i) confirming
and extending to more cations the results obtained so far and of (ii) examining the influence of the
nature of the medium (NO3- or Cl-) on the stoichiometries and the stability of the complexes formed.
Thus complexation has been followed by direct absorption spectrophotometry in methanol in presence
of either 510-2 M nitrate or chloride anions.
With the propoxy derivative E16, the spectral changes induced by the complexation are greater in
chloride medium. They are also more important for La3+ in nitrate medium and for Yb3+ in chloride
medium. In both media, they clearly show the formation of two different species with all cations. The
numerical treatment of these spectra confirmed the presence of two species with the 1:1 and the 2:1
(M:L) stoichiometry. The corresponding stability constants are given in Table 2 of Annex 4.
Consistently with the extraction results, there is a decrease of the stability constants from La3+, to Eu3+
and Yb3+, which is more pronounced in presence of chloride anions than in presence of nitrate anions.
In addition there is a strong anion effect on the stability of the complexes, which is higher in chloride
medium (e.g. log 11 = 3.3 for Yb3+). This may be interpreted assuming some interactions of nitrates
with the cation in the complex.
With the more flexible methoxy derivative E15 two 1:1 and 1:2 species also form with Eu3+. With both
ligands, the stability of the Eu3+ complexes is quite similar in chloride medium. However, E15 forms
less stable complexes in nitrate medium (log 11 = 1.6 and log 21 = 2.9).
Substitution of the amide functions .
In order to observe the effect of the N-methylation of the CMPO functions of compound E9, the related
compound E10 has been studied in extraction (Annex 4:Table 3) and complexation (Annex 4:Table 2).
The consequence of this substitution is (i) a strong reduction of the extraction levels of lanthanides
with respect to E9 : %E are lower than 10; comparatively the percentage extraction of La3+ by E9 was
98% in the same experimental conditions (CM = 10-4M and CL = 10-3M); (ii) a loss of selectivity along
the series. Consequently E10 becomes a better extractant of Yb3+ than E9. Th4+ requires just 1/10 of
the ligand concentration to reach %E values similar to those of lanthanides.
Ligand E10 forms 1:1 complexes only, in contrast with E9, for which 2:1 complexes were also
observed (Annex 4:Table 2). However the small differences in stability constants give no real
explanation for the much better extraction of E9. The complexes are much stronger in chloride than in
nitrate medium (log 11 = 2). Similar results are found in acetonitrile: again there is exclusive
formation of a 1:1 complex with E10 (log 11 = 5.50.2), while for E9 the additional formation of the 1:2
species is still observed (log 11 = 6.10.1, log 21 = 11.80.2). Contrary to what could be expected
from the solvating properties of both solvents the stability constants in acetonitrile are of the same
order or slightly lower than those determined in methanol.
Influence of the number of CMPO arms
In order to get some information about the number of CMPO arms involved in the binding of
lanthanides, calix[4]arenes partially substituted with CMPO have been synthesised and studied,
particularly the mono CMPO E14 and the tri CMPO E13. Extraction results and those obtained in the
57
previous contract for the corresponding di-CMPO calixarenes show that the best extraction level is
achieved when four CMPO arms are available, i.e. E% for Eu3+ is only close to 50 with E13, whereas it
is 100 for E9 (Annex 4:Table 3). The comparison of the results obtained for E13 with those obtained
before for the linear trimer E18 shows the lower efficiency of the calixarene over the acyclic
compounds (e.g. for Eu3+ and CL = 10-2 M, %E = 48 and 94, respectively). A possible explanation can
be the dependence of D on the concentration of the ligand. A slope of nearly 2 in the plot of log D vs.
log [L] suggests the formation of a 1:2 species. The arrangement of two ligands molecules around a
europium cation is more easily achievable with the linear trimer than with the calixarene. A change in
the slope for E13 indicates different compositions of the extracted species for lower ligand
concentrations. Formally the slope suggests a 2:1 complex for CL< 510-3 M. It seems that for ligand
concentrations lower than 10-3 M, the calixarene is a better extractant than its linear analogue.
Four arms seem hence necessary to obtain extraction performance. However, the compound E122 in
which the fourth arm is replaced by an acetamide function, displays percentage extraction
intermediate between the tetra and the tri-CMPO calixarene. With this compound the selectivity in the
series is maintained contrary to the tri-CMPO derivative (Annex 4:Table 3).
The spectrophotometric titrations in methanol suggest the formation of two complexes in chloride
medium with E13. The stability of these complexes is too high to be precisely evaluated. However in
nitrate medium where the complexes are generally less stable, only 1:1 complexes form, the stability
of which decreases from La3+ (Annex 4:Table 2). The formation of 1:1 complexes of similar stability
has also been shown with E122.
3.2.3.2 Narrow rim CMPO calix[4]arenes
The high efficiency for lanthanide and thorium cations of calix[4]arenes substituted at the narrow rim
has been shown to depend on the length of the CH2 chain linking the phenolic oxygens to the
functional groups. The derivative with n = 4 was shown to be the best extractant. In order to see if it
was possible to tune the efficiency and possibly the selectivity of this series of compounds, mixed
derivatives bearing two different chain length have been studied: E8 (n=3,4), E6 (n=3,5) and E7 (n=4,5). Extraction data obtained with E8 are similar or slightly lower than with the homo derivative
(n=4) but much higher than with the derivative (n = 3). E6 and E7 display extraction percentages
intermediate between those of the corresponding symmetrical derivatives (Annex 4:Table 3).
Complexation in methanol in presence of chloride anions has been followed for two “symmetrical”
ligands E4 (n=3) and E5 (n=4) and for the mixed E8 and E6 (Annex 4:Table 2). Only 1:1 complexes
form with the four ligands. With the “symmetrical” ones, the stability sequence is: La3+ > Eu3+ Yb3+.
With the mixed E8 the stability decreases along the series, whereas E6 is almost not selective.
The calix[6]arene substituted at the narrow rim by CMPO residues (E21) revealed not soluble enough
in dichloromethane and methanol and thus could not be studied in extraction and complexation.
3.2.3.3 Influence of the conformation : 1,3-alternate and 1,2-alternate CMPO calix[4]arenes
All CMPO compounds reported above are in the cone conformation. Exploiting the possibility of
calixarene to adopt other conformations, compounds E17 and E19, in the 1,3-alternate conformation
and E20 in the 1,2-alternate conformation were synthesised. In E17, two opposite positions of the
58
narrow rim are substitued by CMPO functions as well as the two others at the wide rim on the same
side, whereas in E19 and E20 both sides of the molecules are substituted and the molecules can be
considered as possible ditopic complexing agents.
Among these compounds, E20 is surprisingly very efficient for La3+ and Eu3+ even at CL=10-4 M (Annex
4:Table 3). It is also very selective in the series with a selectivity factor expressed as the ratio of the
distribution coefficients of 6.2 between La3+ and Yb3+. The extraction of Th4+ in equimolar conditions of
concentration in metal and ligand is almost quantitative. This ligand is thus much more efficient than
the wide and narrow rim derivatives. In contrast, lanthanides are poorly extracted by E17 with almost
no selectivity. The ditopic E19 is a better extractant but is not selective either.
The study of the complexation in methanol led to very interesting results concerning the
stoichiometries of the complexes formed. In presence of chloride, the spectrophotometric changes
suggest the formation of three complexes of high stability with E17. In presence of nitrates, only a 1:1
species forms with the three lanthanides, the La3+ complex being the most stable. With E19, an
additional 3:2 complexes must be taken into consideration to obtain a good fit of the experimental
data. Further ESI-MS experiments are planned to confirm the presence of this complex. With Ag +
cations also studied because of its potential use as auxiliary cation in potentiometric experiments,
there is formation of 1:2 complexes with both ligands.
3.2.3.4 Resorcinarenes
Four CMPO substituted resorcinarenes, differing from the nature of the substituents on the phosphine
oxide functions (phenyl (E28 and E29) or ethoxy (E45 and E46)) and substituted or not on the amide
nitrogen, showed (i) low extraction levels for lanthanides (%E = 5 - 14, for CL = 10-4 M, a low
concentration used because of low solubility of the ligands); (ii) no significant selectivity (Annex
4:Table 4). They revealed less efficient in extraction than their calixarene counterparts. Complexation
of lanthanides in both methanol and acetonitrile was hindered by the formation of precipitates during
the spectrophotometric titrations.
3.2.4 Calix[4]arene picolinamides and TTFA Among several picolinamide calixarenes received only two tetramers, the narrow rim derivatives E52 and E54, could be studied in complexation in methanol, the others being not soluble enough in this
solvent. Stable 1:1 and 1:2 complexes were found with similar stability along the series (Annex 4:Table
5). The results also show that the chain length between the phenolic oxygens and the functional
groups has almost no influence on the complexing properties, as the complexes formed by the two
ligands have similar stability.
TTFA calixarenes were not stable enough in methanol and acetonitrile to allow complexation studies,
except for E90, for which the percentage extraction is ranging from 9 to 14 in the lanthanide series.
This compound revealed to be instable in methanol and acetonitrile.
59
3.3 NOVEL EXTRACTANTS FOR SELECTIVE EXTRACTION (MICROMOD)
3.3.1 General strategyHighly porous magnetic silica particles were shown to be promising solid phases for the extraction of
lanthanides and actinides. The general strategy of magnetic separation of radionuclides from
radioactive wastes includes the selective complexation of long-lived radionuclides on the surface of
magnetic particles with covalently attached selective supramolecular ligands on their surface. After
magnetic separation of the radioactive particles the radionuclides have to be back extracted. Thus the
chelator containing particles can be re-used in the extraction process to minimize the costs.
For this purpose the magnetic particles must be stable under extreme real waste pH conditions.
Therefore the magnetic particles were coated with an additional silica layer to protect the incorporated
iron oxide from interaction with the waste media and to introduce the functional groups for the chelator
binding.
The comparison of different types of magnetic and non-magnetic silica particles with various diameters
of 1 – 100 µm and various porosities showed the most effective immobilization of various chelators on
the surface of highly porous magnetic silica particles. These particles with a diameter of approximately
100 µm have a surface of about 3.3 · 1010 µm²/ mg and were used for all chelator immobilizations in
the 2nd and 3rd year of the project.
The following types of selective chelators for Eu, Am or Cs were covalently attached on the surface of
magnetic silica particles:
mono- and di-CMPO derivatives (with Mainz),
CMPO calixarenes (with Mainz),
cosans (with IIC/Katchem),
functionalized dendrimers (with Mainz, Parma, Twente and Madrid)
dendrimers with mixed chelating sites on their surface (with Mainz, Parma and Twente).
The most efficient binding method between chelator and particle surface was found to be the reaction
of chelator molecules containing terminal amino groups with magnetic particles which were
functionalized with dichlorotriazinyl groups. This covalent binding strategy was used for the
immobilization of all chelators containing terminal amino groups.
3.3.2 Extraction studies with magnetic particles at CEA, CadaracheThe calculation of the extraction coefficients KD for solid-liquid extraction was derived in analogy to the
liquid-liquid extraction experiment:
For liquid/liquid extractions the distribution coefficient KD is defined as
60
. Equation 9
For solid/liquid extractions the extracted amount of substance must be related to the mass of the solid
phase:
. Equation 10
Since the extracted amount is usually determined by its decrease in the liquid phase
Equation 11
this leads to
. Equation 12
Due to saturation phenomena, these KD values are usually not constant. Thus only values obtained
under identical conditions (concentration in the liquid phase, amount of solid phase) should be
compared.
Therefore the distribution coefficients for Eu and Am extraction with magnetic particles were
determined under constant conditions. In a typical experiment 300 mg magnetic particles (mS) was
treated with 10 ml (VL) Eu or Am containing waste solution of a known activity (cL,0). This magnetic
particle suspension was shaken for 1 hour at room temperature. After magnetic separation of the
particles the final radionuclide activity (cL) was measured in the supernatant. Results are given in
Annex 5.
3.3.2.1 Extraction of radionuclides with magnetic particles containing mono- and di- CMPO derivatives on the surface
The mono-CMPO compounds E146 and E145 and the di-CMPO compound E148 as well as the p-
nitrophenol active ester of CMPO were received from the Mainz group. These compounds with
terminal amino groups were immobilized on the surface of the magnetic particles via dichlorotriazinyl
functions. The extraction of Am and Eu with these magnetic particles was studied at CEA.
The distribution coefficients for Am and Eu were rather low (< 4 ml/g) for the simple CMPO-
functionalized particles as well as for the particles with the mono-CMPO derivative E146 and the di-
CMPO derivative E148. The prolongation of the spacer length between the particle surface and the
61
chelator group from 3 C atoms (E146) to 5 C atoms (E145) lead to close on 10-fold higher distribution
coefficients for Am and Eu.
These particles are reference materials for comparison of the extraction data obtained with the CMPO-
calixarene and CMPO-dendrimer particles.
A further improvement of the Am and Eu extraction capacity of magnetic particles was achieved by
fixation of CMPO functionalities on the silica particle surface by polycondensation of the silanol groups
on the particle surface with the triethoxysilane derivative of CMPO (E149 from Mainz). This strategy
lead to a significant increase of the Am and Eu distribution coefficients by a factor of about 80 in
comparison to the particles with the other CMPO derivatives E146, E145 and E148. The reason for
this improved extraction behavior can be explained by an optimal preorganization of the CMPO
molecules given by the silica skeleton on the particle surface.
3.3.2.2 Extraction of radionuclides with magnetic particles containing CMPO calixarenes on the surface
Calix[4]arenes bearing four CMPO-functions on their wide rim and aminoalkyl groups on the narrow
rim (received from Mainz) were covalently bound on the surface of magnetic particles via
dichlorotriazinyl groups. The influence of the length of the spacer between particle surface and
calixarene, as well as the influence of the number of linkers between the particle surface and the
calixarene on the Am and Eu extraction capacity of the particles were studied. Therefore the following
CMPO-calix[4]arenes were immobilized on the surface of the standard particles:
The amount of CMPO-calixarene bound to the surface in this step was determined monitoring its
disappearance from the liquid phase by UV-spectrometry. Independent on the variation of the spacer
length and number the binding capacity of the magnetic particles had a nearly constant value of 25 +/-
3 µmol calix[4]arene per g of particles. This result is surprising since obviously there is no measurable
influence of the number of linkers (one, two or four) nor of the length of the spacer (3, 5 and 10 C-
atoms). The available surface of the particles, determined by the BET-method is 3.3·10 19 nm2/g. This
leads to an average area of 2.2 nm2 per calix[4]arene molecule which corresponds more or less
exactly to the area estimated by molecular modelling. It can be assumed therefore that the surface is
completely covered by calix[4]arenes in a kind of densest packing.
The extraction of Am and Eu is much more efficient with particles coated by calix[4]arene derivatives
than for particles coated with the mono-CMPO model compounds E145 or E146. With a factor of >
100 this is most pronounced for CMPO-calix[4]arene E150 in comparison with E146 (both with C3
62
Calixarene Number of linkers Spacer length
E150 2 3 C atoms
E151 2 5 C atoms
E152 2 10 C atoms
E153 1 5 C atoms
E154 4 3 C atoms
spacers). Thus, it is clearly advantageous to preorganize the CMPO-functions on a common platform
(not necessarily a calix[4]arene), and to attach this preorganized assembly to the particle surface.
An increasing spacer length from C3 to C10 between particle surface and calix[4]arene leads to a
steady decrease of KD values for Eu and Am. The comparison of the calixarene attachment via 1, 2 or
4 linkers on the particle surface shows the best extraction results for the attachment via 2 linkers. The
selectivity of Am/Eu lies in the range of 1.6 - 2.8 and remains nearly non-effected by variation of the
calixarene flexibility on the particle surface.
Back extraction experiments under real waste conditions have shown the possibility of a multiple
(more than 5 times) re-use of the magnetic particles with CMPO-calixarenes on the surface without
any loss of extraction capacity.
3.3.2.3 Extraction of radionuclides with magnetic and non-magnetic particles containing cosans on the surface
Cosan dioxane (E159) and cosan bridged chloride (E160 received from IIC Rez) were immobilized on
the surface of acetamide and amino modified magnetic and non-magnetic silica particles, respectively.
Different reaction conditions were studied to achieve an optimal cosan binding on the particle surface.
Cs distribution coefficients of about 100 ml/g were obtained for particles made by attachment of cosan
bridged chloride on the surface of aminofunctionalized particles. Cs / Eu selectivities of about 30 show
that the immobilization of cosan derivatives on the surface of magnetic or non-magnetic particles is a
promising strategy for the development of Cs selective extraction agents. Therefore the application of
non-magnetic particles is important for column chromatography processes to separate the
radionuclides from the waste water beside the application of magnetic separation techniques.
3.3.2.4 Extraction of radionuclides with magnetic particles bearing functionalized dendrimers
Dendrimers with one chelator-type
The attachment of dendrimers with terminal amino groups on the surface of magnetic particles was
initiated by Volker Böhmer from the University of Mainz.
For initial studies dendrimers of the 3rd, 4th and 5th generation (DAB-Am-16, DAB-Am-32 and DAB-Am-
64, all from Aldrich) were immobilized on the surface of magnetic particles. This dendrimer coating
lead to an increase of the density of amino groups from 50 µmol/g for simple amino functionalized
particles to about 450 – 550 µmol/g for corresponding dendrimer coated particles. The density of
amino groups on the particle surface was determined by electrokinetic measurements of the
zetapotential and streaming potential. Therefore polyelectrolyte titrations of the magnetic particle
suspensions against a sodium polyethylene sulfonate standard solution of known concentration were
carried out until reaching the electric zero point of charge to obtain the concentration of amino groups
on the particle surface. The amount of consumed polyelectrolyte solution was used to calculate the
density of amino groups on the particle surface.
The dendrimer coated magnetic particles have a high potential for immobilization of a large variety of
selective chelators in a very high density on the particle surface. For comparative studies the
dendrimer of the 3rd generation was attached on the surface of magnetic particles by reaction of amino
63
groups of the dendrimer with dichlorotriazinyl groups on the particle surface to get a standard type of
dendrimer particles for the immobilization of different types of chelators.
The attachment of CMPO groups was realized by the reaction of the p-nitrophenol ester of CMPO (
E147 received from University of Mainz) with the amino groups of the dendrimer coated particles. The
CMPO binding capacity of dendrimer coated particles in comparison to simple amino functionalized
magnetic particles without a dendrimer spacer was increased by a factor of 100. This leads to a
significant increase of the distribution coefficients for Am and Eu by a factor of 50 for magnetic
particles with and without the dendrimer spacer. Analogous CMPO-dendrimer modifications were
carried out with non-magnetic silica particles for potential use in column chromatography applications.
Picolinamide structures were introduced on the surface of dendrimer coated particles by reaction of
pentafluorophenyl active ester of picolinic acid (E155 received from Parma), The distribution
coefficients for Am and Eu are extremely high at pH=3 (up to 18 000 ml/g), but decrease significantly
at lower pH values. Thus it would be very important for the future to synthesize a picolinic acid
analogous structure with improved complex stability at pH=1. Furthermore thenoyl sulfonamide
structures were introduced on dendrimer modified silica particles by reaction of thenoyl sulfochloride
(E156 received from Parma) with the amino groups of the dendrimers. The distribution coefficients for
the Am and Eu separation with these particles are rather low (< 5 ml/g), but show a more than 4-fold
increased Am / Eu selectivity in comparison to the corresponding particles without a dendrimer spacer.
A malonamide-functionalized dendrimer particles were obtained by carbodiimide activation of the
carboxylic acid group of the malonamide derivative (E157 received from Madrid) followed by reaction
with the amino groups on the dendrimer-particle surface. The extraction properties of these
malonamide functionalized dendrimer particles were studied at CIEMAT.
TODGA analogous derivatives (E158 received from Twente) were also immobilized on the surface of
the dendrimer coated particles. This lead to a 300 – 400 fold increase of the Am and Eu distribution
coefficients KD in comparison to corresponding particles without the dendrimer spacer.
All investigated chelator immobilizations on dendrimer coated silica particles show a significant
increase of the extraction properties of the silica particles by introduction of the dendrimer spacer
resulting in much higher densities of chelating groups on the particle surface.
Back-extraction / Recycling studies with CMPO- and TODGA-functionalized dendrimer
particles
The possibility of multiple recycling of CMPO or TODGA modified dendrimer particles was shown
under real waste conditions. 10 successive extraction/stripping steps of europium (from 3M HNO 3)
were carried out with CMPO-functionalized dendrimer beads. Generally more than 90% of Eu activity
were recovered by stripping beads twice with demineralized water (for the 3rd stripping the 152Eu
activity was negligible). The extraction capacity of the beads was decreased by 20 - 30 % after 10
successive extraction/stripping steps.
Two successive extraction/stripping steps of europium and americium (from 3M HNO3) were carried
out with TODGA-functionalized dendrimer beads. After the first Am / Eu extraction with the TODGA-
dendrimer particles the radionuclides were back-extracted by shaking the particles in water with a
64
nearly 100 % yield. The recycled particles were used for a second extraction experiment with slightly
higher distribution coefficients in comparison to the first extraction cycle.
Dendrimers with mixed chelating sites
First attempts were made to immobilize different types of chelators on the surface of dendrimer coated
magnetic particles to investigate possible co-operative effects at the radionuclide complexation. Thus
CMPO and a TODGA analogous derivative were attached on dendrimer coated particles with varying
CMPO / TODGA ratios. The amount of covalently attached chelators on the dendrimer-particle surface
was measured by monitoring its disappearance from the liquid phase by UV-spectrometry. The Am /
Eu extraction results show that increasing amounts of the TODGA derivative lead to an increasing
selectivity of the particles for europium over americium, which is typical for particles containing only
the TODGA derivative on the surface. The distribution coefficients for Eu and Am were not increased
by co-operative effects of the different ligands. In the case of combination of the TODGA analogous
derivative with picolinamide structures on the particle surface, or with CMPO and picolinamide
structures a decrease of the extraction capacity of the dendrimer coated magnetic particles was
observed in comparison with the dendrimer coated particles bearing on one type of chelator.
Repeated extraction / stripping steps also show in this case the possibility to recycle the magnetic
particles without any loss of extraction capacity for Am or Eu.
3.3.3 ConclusionThe general strategy of magnetic separation of radionuclides from radioactive wastes with
functionalized magnetic particles was shown to be a promising alternative to the commonly used
liquid-liquid extraction techniques. The selective complexation of long-lived radionuclides on the
surface of magnetic particles was achieved by covalent attachment of selective supramolecular
ligands on their surface. After magnetic separation of the radioactive particles the radionuclides were
back-extracted nearly without any decrease of the extraction yield. The magnetic particles were stable
under the highly acidic conditions at the Am and Eu extraction (3 M HNO 3). Thus the chelator
containing particles can be re-used in the extraction process to minimize the costs.
Highly porous magnetic and non-magnetic silica particles with a mean diameter of 100 µm were found
to be the most efficient particle type for the extraction studies. This particle type has a high density of
functional groups for the binding of chelator molecules. Analogous non-magnetic silica particles were
investigated in comparison to the corresponding magnetic particles to study the possibility of column
chromatography applications of these particles for radionuclide removal from waste waters.
The extraction of Am and Eu with magnetic and non-magnetic silica particles bearing CMPO-
calix[4]arenes on the surface was increased by a factor of 100 – 300 (distribution coefficients of Am
and Eu) in comparison to the reference particles with directly attached CMPO-molecules. Thus it is
clearly advantageous to pre-organize the CMPO functions on a common platform, and to attach this
pre-organized assembly to the particle surface.
A short spacer with 3 C atoms between calixarene and particle surface was shown to be
advantageous for the Am and Eu extraction in comparison to longer C5 or C10 spacers. The
65
attachment of the calixarene via two linkers on the particle surface gave better extraction data than the
very flexible attachment of the calixarene by only one linker, or the strong fixation of the calixarene by
4 linkers.
The covalent attachment of dendrimers with a high number of terminal amino groups on the surface of
porous silica particles allowed the binding of selective chelators for radionuclides in a high density.
The dendrimer coated particles were used as universal platform for the covalent binding of chelator
molecules like CMPO, picolinamide, thenoylsulfonamide, malonamide or TODGA analogous
derivatives. The introduction of the dendrimer spacer lead to a 50- to 400-fold increase of the
distribution coefficients for the Eu and Am extraction in comparison to the reference particles without
the dendrimer.
Dendrimer coated particles were functionalized with two or three different types of chelators to study
possible co-operative effects at the radionuclide complexation on the particle surface. The variation of
the CMPO / TODGA ratio on the surface of the dendrimer particles did not influence the size range of
the Am and Eu distribution coefficients significantly in comparison to the dendrimer particles with only
CMPO or only TODGA on the surface. But the selectivity for Am over Eu which is typical for CMPO
dendrimer particles was reduced by increasing TODGA / CMPO ratios until a turn over of the
selectivity to Eu over Am. These Eu / Am selectivities of 3 are typical for TODGA dendrimer particles
and were obtained if the TODGA concentration on the particle was higher than the CMPO
concentration. The additional introduction of picolinamide chelators on the surface of TODGA or
TODGA / CMPO dendrimer particles lead to a loss of extraction capacity of the beads due to the low
pH stability of the Am and Eu complexes of picolinamide structures.
The immobilization of cosans on the surface of magnetic and non-magnetic particles were shown to be
a promising strategy for the solid-liquid extraction of Cs. With initial Cs / Eu selectivities of about 30
and distribution coefficients of about 100 ml/g the immobilization of cosan on particles should be
further developed.
Future studies should include studies to scale-up the solid-liquid extraction process with magnetic and
non-magnetic particles. Therefore the dependence of the Am and Eu distribution coefficients on the
mass of particles per constant volume of waste water have to be studied to determine the exact
binding capacity of the particles.
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3.4 EXTRACTION RESULTS ON COSAN DERIVATIVES (NRI) In the framework of this extended CALIXPART project, tests of new synthesized extraction agents
were carried out. Predominant part of these compounds is formed by functionalized calixarenes
(resorcinarenes). Calixarenes are modified by different function groups containing donor atoms of
nitrogen, oxygen or phosphorus possessing complexing ability towards tervalent lanthanides and
actinides. Their molecules were additionally modified at IIC Rez by substituents of cobalt
bisdicarbollide with the aim to exclude addition of anion for the extraction of complexes of studied
metals. Molecular structure of tested compounds is given in IIC Rez part (see §2.1 p:12) and in Annex
1.
At NRI Rez, the following experimental studies were carried out:
extraction tests of compounds synthesized at ICC Rez based on precursors synthesized by
EU cooperants - universities of Mainz, Twente and Parma
sorption tests of sorbents prepared at MICROMOD
extraction tests of synergic mixtures of calixarene precursors with cobalt dicarbollide.
3.4.1 Extraction tests of precursors and extractants prepared at IIC RezThe basic synthon (t-butyl-calix(4)arene) used for extractant synthesis at IIC Rez was commercially
available, and does not present in acidic media any important complexing ability towards Ln(III) and
Ac(III). This molecule was modified by different number of cobalt dicarbollide (cosan) substituents to
provide anions for compensation of charged metal complexes.
Extraction tests both of extractants containing the two components in different ratio and synergic
mixtures of precursors were carried out. Extraction results are presented in Tables 4 and 5.
Tables 4: Effect of modification of t-butyl-calix(4)arene by COSAN on Eu and Cs extraction
Extractant E112 DEu DCs
2,7 mg HB 0,0032 27,1
2,2 mg calix(4)arene 0,0014 0,0205
2,7 mg HB + 2,2 mg
calix(4)arene
0,0046 6,34
4,9 mg E112 2,43 43,9
E112 (calixarene:dicarbollide = 1:2), Eu extracted into toluene, Cs extracted into nitrobenzene, 0,1M
HNO3, HB – acidic form of basic cobalt dicarbollide
67
Table 5: Effect of modification of t-butyl-calix(4)arene by COSAN on Eu and Cs extraction
Extractant DEu DCs
3,2 mg HB 0,0025 42,4
1,8 mg calix(4)arene 0,0004 0,343
3,2 mg HB + 1,8 mg calix(4)arene 0,0089 40,8
4,9 mg E112’ 1,55 24,9
E112’ (calixarene:dicarbollide = 1:3), Eu extracted into toluene, Cs extracted into nitrobenzene, 0,1M
HNO3
Extraction of Eu by individual components and their synergic mixtures is quite negligible, however,
synthesized extractants exhibit distribution ratios higher by app. three orders. More effective extractant
(both for Eu and Cs) seems to be that with molar ratio calixarene:cosan = 1 :2. The expected better
extraction with direct charge compensation of three cosan substituents was not fulfilled. Of importance
is the fact that the prepared extractants (and their synergic mixtures) could be dissolved in less polar
solvents (like toluene) where cosan itself is not soluble. Results for different solvents indicate the
preference for nonpolar solvents at europium extraction, for cesium extraction the reverse is true.
The influence of acidity on Eu and Cs extraction can be seen from results in Table 6.
Table 6 The influence of acidity on Eu and Cs extraction by E112 in toluene
DMe
CHNO3 0,001 0,003 0,01 0,03 0,1 0,3 1,0 3,0
DEu 2820 670 154 36,8 1,33 0,0386 0,0034 0,0009
DCs 129 102 36,5 13,1 7,68 1,34 0,380 0,0261
5.77.10-4 M of E112 in toluene
Eu extraction decreases with increase of acidity with increasing slope of extraction curve, at 1M HNO 3
the extraction is practically nebligible. The slope of Cs extraction curve (app. -1) indicates mechanism
of ion exchange.
The increasing extractant concentration leads to increased extraction of both elements, with the slope
of 1-2 for europium and 1 for cesium. This fact could lead to technically acceptable extraction ratios
even from media of high acidity. A less pronounced negative influence exhibits the presence of sodium
ions, at 3M NaNO3 the extraction of Eu is still sufficiently high.
Extractant E112 seems stable in media of 1M nitric acid, no decrease in distribution ratios was
observed in five cycle experiments (extraction - back-extraction).
The possibility of Am/Eu separation can be derived from results in Table 7.
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Table 7 The dependence of Am/Eu separation on acidity of the aqueous phase
DEu
CHNO3 0,01 0,03 0,1 0,3 1,0 3,0
DAm 110 56,7 0,323 0,0221 0,0217 0,0254
DEu 459 91,1 1,35 0,0414 0,00234 < 10-3
DAm/DEu - 0,623 0,239 0,533 - -
2 mg E112/ml of toluene
Separation ratios are very close to 1 so that no separation can be effectively achieved. Similar values
were obtained for E112’, too.
3.4.2 Extraction tests on extractants prepared at IIC from precursors of Mainz University
Tests of extractants prepared from compounds with technical denominations t-butyl-calix(4)arene,
E120, E167 were performed and the precursors (E168, E120 and E167) were tested in synergic
mixtures with cobalt dicarbollide. Structures of molecules are given in Annex 1.
5.39.10-4 M E115 in toluene, 1 mg RBC189/ml in toluene
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3.4.4 Extraction tests of extractants prepared from precursors of Twente university
Substitution of Twente precursors by cobalt dicarbollide led again to compounds with low extraction
efficiency for Eu (compounds E108, E109, E110, E111, E139). Europium could be again effectively
extracted only from solutions of low acidity, see Table 12.
Table 12 Europium extraction with some derivatives of Twente precursors
DEu
CHNO3 0,001 0,01 0,1 1,0
E108 724 22,7 0,0249 0,00136
E109 6,99 0,194 0,00662 < 10-3
3.98.10-4 M E108 in toluene, 5.77.10-4 M, E109 in toluene (not fully dissolved)
3.4.5 Tests of MICROMOD sorbentsSeven individual sorbents containing molecules of cobalt dicarbollide attached to amino group via
opened dioxanate or phosphorus bridge were synthesized. Sorbent particles were either magnetic or
based on SiO2. Regardless to relatively high cosan content, very poor sorption results for Eu and Cs
were obtained as can be seen in Annex 5.
3.4.6 ConclusionsOn the basis of obtained results, the following conclusions could be made:
in system of t-butyl-calix(4)arene with cobalt dicarbollide, calixarene derivatives are much more
effective for Eu extraction than their synergic mixtures
using functionalized calixarenes, synergic mixtures of calixarene and cobalt dicarbollide are very
effective for Eu extraction
for all tested compounds, no effective separation Am/Eu can be achieved.
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3.5 SOFT DONOR LIGANDS AND NMR STUDIES (LIEGE UNIVERSITY)
3.5.1 Synthesis and extraction properties of calix[4]arene ligandsThree different substituents have been added to the calix[4]arene units with the Am(III)/Eu(III)
separation in view. These substituents were selected because they feature soft donor atoms such as
sulfur or nitrogen that are susceptible to form slightly more covalent bonds with the trivalent actinides.
The synthesis, properties and extraction behavior of calixarenes substituted with acyl thiourea,
pyrazolone and tetrazole groups are reported in this chapter.
The macrocyclic extractant E107 bearing four 3-benzoyl-thioureio functions has been obtained in good
yields from calix[4]arene in four steps. The monomeric analogue E97 has also been synthesized for
comparison purposes.
Extraction of trivalent 152Eu and 241Am ions into CHCl3 by E107 and E97 were performed in the
presence of a synergistic agent (TOPO) at pH 3. Reasonable extraction coefficients were obtained but
the Am(III)/Eu(III) separation was very poor. Moreover, non-cyclic E97 is a better extractant than E107 in contrast to what was expected. Calixarenes are indeed known to be much better extractants than
their monomeric analogues but there are apparently exceptions to this rule.
3.5.1.2 Sulfur-containing substituents: acyl pyrazolones and acyl thiopyrazolones
In view of the poor effectiveness of E107, it was decided to graft acyl thiopyrazolone groups on the
narrow rim of calix[4]arene (E82, E83,E84). According to literature data, very high Am(III)/Cm(III)
separation coefficients are reached with E83 in presence of a phenanthroline derivative in a
synergistic system.
However, ligand E84 proved to be poorly selective and chemically unstable. The formation of sulfur-
sulfur bonds was easily observed by Raman spectroscopy. It was also showed that these bonds are
readily broken by the addition of Na2S. Extractions could thus be performed with the pure compound
after a chemical treatment. The poor selectivity of E84 was surprising in view of the literature data and
it was decided to test the extraction ability of the reference compound E83. Am(III)/Eu(III) separation
coefficients of 10-15 were obtained in various conditions after checking thoroughly the purity of E83 by
various methods including a Raman spectroscopic method specially developed for this purpose.
Although a reasonably effective separation of Am(III) and Eu(III) was achieved, the separation is not
as high as reported in the literature ( ~ 100) and thiopyrazolones are probably not as effective as
claimed.
New synthetic procedures were also developed for obtaining acyl pyrazolones substituted on the wide
or the narrow rim of calix[4]arene as in E82. Very high distribution coefficients are obtained with these
compounds at pH 3 but they do not allow a good actinides-lanthanides separation presumably
72
because they feature only oxygen atoms. However, it was found that E82 forms a very unusual mixed
Na-Yb complex in which the two metal ions shared four oxygen atoms and are located on a fourfold
symmetry axis. In the crystallographic structure depicted in Figure XVIII, the Yb(III) and Na(I) ions are
only 2.5 Å apart even though they are both positively charged. The Na(I) ion is in fact the counter ion
needed to ensure the electrical neutrality of the complex. The presence of sodium has been checked
by potentiometry and by neutron activation. The large chemical shifts observed by solid state 23Na
nuclear magnetic resonance also indicate that the ligand encapsulates sodium. Moreover, it was found
that a single crystallographic cell contains two enantiomers with opposite helicity. An NMR study
showed that the pyrazolone substituents form one helix that is favored at low temperatures while
another helical structure is found at elevated temperatures. This is not the classical exchange between
two helical forms but an unusual temperature-dependant stabilization of different structures.
Figure XVIII. Crystallographic structure of the Yb(III)-Na(III) complex with ligand E82.
The encapsulation of a sodium ion into the above structure seems to also take place during the
extraction of Am(III) and Eu(III). As shown in Figure XIX (right), sodium ions and to a lesser degree,
potassium ions strongly enhance the extraction of Eu(III) and Am(III) by comparison with Cs(I) and
Li(I) and there is no effect of the alkali ions if the extractions are carried out with the non-cyclic
monomeric analogue of E82 (left Figure XIX). To our knowledge, this is the first example of an
extraction of an electrically neutral heterometallic complex. The selective encapsulation of Na(I) by
E82 has been confirmed by quantum mechanical studies carried out by G. Wipff (see §3.6 p:76) and
the complexation of lanthanides has been investigated by potentiometry by F. Arnaud (see §3.2 p:54)
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Figure XIX. Extraction of Eu(III) and Am(III) by ligand E82 (left) and its non-cyclic monomeric
