M. Verdaguer, Emeritus ProfessorChimie Inorganique et Matériaux Moléculaires, C.N.R.S. Unit 7071
Université P. et M. Curie, Paris, [email protected]
SYNTHETIC ENDEAVOURS TOWARDS
NEW SINGLE CHAIN MAGNETS
NEW SINGLE MOLECULE MAGNETS and
International Workshop on « Physics on Nanoscale Magnets », Kyoto, 1-4 December 2003NAREGI Project, Kyoto Garden Palace Hotel
SYNTHETIC ENDEAVOURS TOWARDS
Recents Results, Promises, Problems and Prospects
NEW SINGLE CHAIN MAGNETS
NEW SINGLE MOLECULE MAGNETS and
Coworkers and CollaboratorsV. Marvaud1, M. Julve2, F. Villain1, W. Wernsdorfer3
F. Tuyèras1, R. Lescouezec2, J.M. Herrera1, L.T. Marilena2, R. Tiron3
N. Galvez1, R. Garde1, M. Hernandez1
1) CIM2, CNRS Unit 7071, Université Pierre et Marie Curie, Paris, France2) Departament de Quimica Inorganica, Universitat de Valencia, Burjassot, Spain
3) Laboratoire Louis Néel, CNRS, Grenoble, France
• Introduction :- molecular magnetism- the molecular approach to nanosystems
• What a chemist must & can control ?• From High Spin Molecules to SSM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets• Conclusions
Outline
Chemistry …
• Science of matter’s transformation
• A way to transform the world …
Reactants Products
A + B CT, P, Solvent,pH …
M. Noyori, Hanoi, october 2003:
To daythe chemist is able
to synthesizeany molecule
at will
Chemistry …
How to choose A and B ?
or : which target C ?
A + B C
Chemistry …
which target C ?A + B C
-1- to make money … (not always rewarding …)
-2- to follow your supervisor … (not always recommendable …)
-3- to answer questions of physicists ! or others …… (sometimes amazing and useful)
-4- to achieve a synthetic challenge !… (difficult but worth of the candle)
-5- Many more …
a scientific discipline that conceivesdesigns synthesizesstudies and uses new molecular magnetic materials …
Molecular Magnetism
One possible answer comes from
In a multidisciplinary way …
One of the nests of Molecular Magnetism
« Olivier Kahn was one of those who allowed to switch from magnetochemistry to molecular magnetism »
D. Gatteschi, Lausanne, �2001
Answering questions of physicists …
the strange and successful story of Haldane gap …
Synthesis
Properties
Theory
Idea
NewMaterials
NewFunctions
NewConcepts
… Haldane gap
Conjecture(1983)
« Dynamic mass generation by the Néel magnon is predicted … »
Very clear and useful indication for synthesis …
« Dynamic mass generation by the Néel magnon is predicted … »
Synthesis
Properties
Theory
Idea
NewMaterials
NewFunctions
NewConcepts
… Haldane gap Energy Gap in AF Integer spins 1D
Uniform Ni(II), S=1 AF Chains
NENP TMNINNINAZ… many others
Conjecture(1982)
« Translation » :
J.P. Renard et al., Europhys. Letters, 1987
One of the central questions …
Is it possible to use molecules(isolated metal complexes)
to build magnets … ?
Achieving a synthetic challenge …
a ferrimagnetic bimetallic molecule-based magnet
at 4.6 K…
M. Verdaguer et al., Coord. Chem. Reviews, 1998,
Overcome entropic and kinetics hindrances …
A-L-B-L-[A-L-B]n-
Synthesis
Properties
Theory
Idea
NewMaterials
NewFunctions
NewConcepts
Synthetic challenge : feasibility of a bimetallicmolecule-based magnet ?
Bimetallic chains
AF Exchange Interactionbetween different spins
BUT …
IT WORKS !
MnCu(dto)2•7.5H2O
OCu
O S
S O
OS
S
2-
O
O
O
N
C
N
O O
O
H X
Cu
OH2
2-
MnCu(pba)•2H2O
OO
H2O OMn
OH2
OH2
CuO S
S
OO
OH2
Mn
OH2
OH2
O
OS
S n
O
O
O
N
C
N
O O
O
H X
Cu
O
O
Mn
OH2
OH2OH2 n
Mn
A. Gleizes et al. JACS 1981 et 1984, 3277Y. Pei et al. JACS 1986,
Synthesis
Properties
Theory
Idea
NewMaterials
NewFunctions
NewConcepts
Bimetallic planes
AF between ChainsAfter Displacement
MnCu(pba-OH)•2H2O
O
O
O
N
C
N
O O
O
H X
Cu
O
O
Mn
OH2
OH2OH2 n
Mn
NOW …
Y. Pei et al., J. Am.Chem.Soc., 1988, 782
Molecular Engineering vs Crystal Engineering
O
O
O
N
C
N
O O
O
H OH
Cu
OH2
2-
Cu(pba-OH)
Catena µ-[Cu(II)(pba-OH)Mn(II)(H2O)2] Chain
Y. Pei et al. J. Am. Chem. Soc. 1988, 110, 782 ;
Molecular Engineering vs Crystal Engineering
Ferrimagnetic Bimetallic Chains
Hydrogen bonding Interchain Interactions (af)
Magnet atTC = 4.6K
O
O
O
N
C
N
O O
O
HHO
CuO
O
MnOH 2
H 2 OOH 2
MnO
N
C
N
O
OHH
Cu
OH2
O
OO
O
Mn
OH 2
OH 2
O
O
O
NH
C
NH
O O
O
HO H
CuO
O
MnOH 2
OH 2
OH 2
MnO
NH
C
NH
O
OHH
Cu
OH2
CH3
CH3O
O
MnOH 2
OH 2
O
O
O
N
C
N
O O
O
HO H
CuO
O
MnH 2 O
OH2
OH 2
MnO
N
C
N
O
OHH
Cu
OH2
O
OO
O
MnOH 2
OH 2
Catena µ-[Cu(II)(pba-OH)Mn(II)(H2O)2] Chain
Y. Pei et al. J. Am. Chem. Soc. 1988, 110, 782 ;
Molecular Engineering vs Crystal Engineering
Ferrimagnetic Bimetallic Chains
Hydrogen bonding Interchain Interactions (af)
Magnet atTC = 4.6K
O
O
O
N
C
N
O O
O
HHO
CuO
O
MnOH 2
H 2 OOH 2
MnO
N
C
N
O
OHH
Cu
OH2
O
OO
O
Mn
OH 2
OH 2
O
O
O
NH
C
NH
O O
O
HO H
CuO
O
MnOH 2
OH 2
OH 2
MnO
NH
C
NH
O
OHH
Cu
OH2
CH3
CH3O
O
MnOH 2
OH 2
O
O
O
N
C
N
O O
O
HO H
CuO
O
MnH 2 O
OH2
OH 2
MnO
N
C
N
O
OHH
Cu
OH2
O
OO
O
MnOH 2
OH 2
Achieving a synthetic challenge …
a brief story of a molecule-based magnet …at room temperature
M. Verdaguer et al., Coord. Chem. Reviews 1998, 190, 1023 & Phil.Trans.A, 1999, 357, 2959.
a confidence problem …
NB : no long range order in 1DLet us go to 3D …
Synthesis
Properties
Theory
Idea
NewMaterials
NewFunctions
NewConcepts
Synthetic challenge : feasibility of a room temperature molecule-based magnet ?
Prussian Blue analogues
V4[Cr(CN)6]8/3•n H2O… and many others
Exchange Interaction(1975, 1976)
TC = 315K
QuickTime™ et un décompresseurDV - PAL sont requis pour visualiser
cette image.
Blossoming of the discipline …
O. Kahn Eds. K. Itoh M. Kinoshita
Eds. J. MillerM. Drillon
Eds. W. LinertM. Verdaguer
from magnetochemistry to molecular magnetism …
Synthesis
Properties
Theory
Applications
Switchable SystemsMolecular Magnets
Multifunctional materials« Single Molecule » Magnets
Single Molecule Magnet
Remains oriented after withdrawing of the field(slow relaxation of the magnetisation …)
WITHOUTInteraction between the molecules
Phenomenon strictly molecular !
WHY ?
Synthesis
Properties
Theory
Idea
NewMaterials
NewFunctions
NewConcepts
… Single molecule magnets Giant Molecular Clusters
Mn4and many others
High Spin + Anisotropy? E = DSz
2 Mn12Fe8
Top down
Nanosystems• Nice Chemistry• Single molecule magnets
• Applications (far …)• Recording• Quantum computing
Fragments Threads
Dots
• New Physics• Quantum / Classical• Quantum tunneling
Bottom up
Giant Molecular Clusters
0D, Molecules
3DMetalsOxydes
Nanomagnets : How ?Molecular Clusters
• No dispersion in size, in shape and in orientation
• Systems well characterised : structure, magnetic parameters
• Control of parameters by synthesis
• Solubility• Biocompatibility
Single molecule magnetswithout interaction between the molecules !
High Spin Anisotropic Molecules
z
yx
Magnetisation reversal
Anisotropy Barrier DSz2
and D < 0
Single molecule magnetsz
yx
E
- Sz
Sz+Sz
0
DSz2
0-2-4 +2 +4
Anisotropy Barrier
Tunneling
ThermalActivation
DSz2 = 400K ? |D| = 1K
S = 20(D < 0)
Remark : if DGS > 0
D>0
- Sz Sz+Sz0-2-4 +2 +4
DSz2
Sz=0
Within the ground state, Sz=0 state is at the lowest energy
No more SMM behaviourDGS<0 is necessary for SMM …
E/K
Contro also transversal anisotropy E : mixing of M levels Contro also transversal anisotropy E : mixing of M levels in Fe8 and central for Quantum tunnelingin Fe8 and central for Quantum tunneling
From D. Gatteschi, Florence
H = DSz2 + E(Sx
2 -S2y) + Terms(S4)
• Introduction : molecular magnetism- the molecular approach to nanosystems
• What a chemist must & can control ?• From High Spin Molecules to SSM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets• Conclusions
Outline
• Introduction : molecular magnetism- the molecular approach to nanosystems
• What a chemist must can control ? & can !• From High Spin Molecules to SSM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets• Conclusions
Outline
For the chemistParameters to Control
J = Exchange ConstantIntramolecular interaction
zJ’ = Intermolecular interaction
E
- Sz
Sz+Sz
0
DSz2
0-2-4 +2 +4
Anisotropy Barrier
Tunneling
ThermalActivation
J’J
S = SpinD, E = Anisotropy
Synthetic “Strategy” in Paris
Hexacyanometalate “Heart”Lewis Base
Mononuclear ComplexLewis Acid
Polynuclear Complex
Valérie Marvaud, A. Scuiller, F.Tuyèras, R. Garde, (T. Mallah)
Flexibility of the Synthetic Parameters :
3-
+ 6
2+ 9+
Metallic Cations, Polydendate ligands, Counter-ions, Solvents, Stoichiometry …
Control of the ground spin state• Nuclearity
Control of the intermolecular interaction J ’
Control of the anisotropy
• Electronic anisotropy (nature of the ions)
• Exchange interaction J (F or AF) : Symmetry• Nature of the paramagnetic ions
• Molecular (and Crystal) Structure : Symmetry
• Bulky ligands• Charged complexes and counterions
• Dilution in an diamagnetic matrix
• Introduction : molecular magnetism- the molecular approach to nanosystems
• What a chemist must & can control ?• From High Spin Molecules to SMM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets• Conclusions
Outline
Control of the ground spin state
• Nuclearity
• Exchange interaction J (F or AF) : Symmetry• Nature of the paramagnetic ions
Hexacyanochromate complex
x
z t2g² oct
t2g
eg
Cr(III), d3
[CrIII(CN)6]3-
Orbital Approach
Magnetic Strategy : 1) FERROMAGNETISM
M-C≡N-M'
M C N
M'C N
S = 0, JF = 2k
π σ
Bridge : LargeOverlap DensityJF = 2k, large
Example :
Cr(III) (t2g)3 JF
Ni(II),(eg)2
Cr(III)Ni(II)6S= 3/2 + 6x1
S = 15/2
Magnetic Strategy : 2) FERRIMAGNETISM
M-C≡N-M'
Cr(III)Mn(II)6S= |-3/2 + 6 x 5/2|
S = 27/2
π
π
Sab ° 0, JAF ∝ Sab√(² 2-δ2)
M C N
M'C N
² δ
Overlap = antiferromagnetism
Cr(III) (t2g)3
JAF
Mn(II) (t2g)3
Example
CrCu6S = 9/2
CrNi6S= 15/2
CrMn6S = 27/2
Hexagonal R -3a = b = 15,27 Å; c = 78,56 Åa = b= 90°; g = 120°; V = 4831 Å3
Hexagonal R -3a = b = 15,27 Å; c = 41,54 Åa = b= 90°; g = 120°; V = 8392 Å3
Hexagonal R -3a = b = 23,32 Å; c = 40,51 Åa = b= 90°; g = 120°; V = 19020 Å3
Heptanuclear Complexes
Marvaud, Chemistry, 2003, 9, 1677 and 1692
F AFF
K. Vostrikova, P. Rey et al., JACS 2000, 122, 718
2nd generation
NCM
NC CN
CN
C
CN
N
NCM
NC CN
CN
C
CN
N
NCM
NC CN
CN
C
CN
N
Spin = 2 = Ni(II)(Rad°)2
= Ni(II)(tetren)Spin = 1
Rad°
1rst generation
Complex
Decurtins, Angewandte, 2000Hashimoto, JACS, 2000
Marvaud, Chemistry, 2003, 9, 1677 y 1692
Rey, JACS 2000, 122, 718
Some examples …
S = 27/2
S = 39/2 (AF), 51/2(F)
S = 14/2
Fe2(Ni-R•2)3
Anisotropy A rational control is more difficult !
Two aspects :
- Structural- low symmetry of the cluster- one anisotropy axis : Cnv, Dnh,…
- Electronic- local anisotropy of the magnetic ions Di- exchange anisotropy Di,j
Control of the anisotropy …
• Isolated Ion Anisotropy Di
• Dipolar Interaction• Anisotropic Exchange Di,j
D = ? i ci Di + ? ci,j D i,jCan be computed (“Genio” Programme, D. Gatteschi)
CoNi5
CoNi3
CoCo3
CoCu3
CrNi 5/2
CrNi2
CoCo2 CoNi2CoCu2
7/2
Marvaud et al., Chemistry, 2003, 9, 1677 and 1692 Ariane Scuiller, Caroline Decroix, Martine Cantuel, Fabien Tuyèras …
CrNi2CoCo2
CoCu6
CrNi
CoNi5CrNi3
CoNi2
CoNi3CrNi3
CoCo6
CoCu2
CoCo3CrCo3
CoCu35/2
7/2
9/2
27/2
Anisotropy
High spin
V. Marvaud
CrMn6
CoMn6
CrNi6
15/2
CrCu6
[CrIII(CN)4{CN-NiII(tetren)}2]+Cl- or [BF]4-
« CrNi2 » complexes : molecules
[CrIII(CN)4{CN-NiII(dienpy2)}2]+Cl-
+
+
CrIII, d3, t2g ; NiII , d8, eg
Orthogonality : FerroSpin : 2x1 + 3/2 = 7/2Structural anisotropy
S = 7�/2Anisotropic molecular GdIII …
One of the most difficult problem :
Control of INTERmolecular interactions J’
i.e. crystal engineering
« CrNi2 » complexes : cell packing
0
0.1
0.2
0.3
0.4
0.5
0.6
0 0.5 1 1.5 2 2.5
1/ch
i (1/
T)
T (K)
0
0.1
0.2
0.3
0.4
0 0.5 1 1.5 2
1/ch
i (1/
T)
T (K)
Magnetism : µ-SQUID MeasurementsMagnetic Susceptibility
Easy axisF
Hard axisAF
Coll. W. Wernsdorfer, R. Tiron See R. Tiron et al., Polyhedron, 2002,22, 2247
Simplified scheme of unit cell[Cr(CN)4{CN-Ni(tetren)}2]Cl
H // easy axis
-1
-0.5
0
0.5
1
-0.6 -0.4 -0.2 0 0.2 0.4 0.6
0.04K0.4K0.5K1K2K3K7K
M/M
s
µ0H (T)
-1
-0.5
0
0.5
1
-1.2 -0.8 -0.4 0 0.4 0.8 1.2
0.05K0.6K1K2K4K7K
M/M
s
µ0H (T)
Hysteresis loops vs temperature
H // hard axis
-1
-0.5
0
0.5
1
-0.4 -0.2 0 0.2 0.4
M/M
s
µ0H (T)
Happ
Happ
Happ
-1
-0.5
0
0.5
1
-0.4 -0.2 0 0.2 0.4
M/M
s
µ0H (T)
Happ
Happ Happ
Happ
-1
-0.5
0
0.5
1
-0.4 -0.2 0 0.2 0.4
M/M
s
µ0H (T)
Hysteresis loops vs direction of H
H // easy axis H // hard axisIntermediate
Hysteresis loopsfor 3 samples
H // hard axis
Cr{Ni(tetren)}2
Cr{Ni(tetren)}2 *
[Cr{Ni(dienpy2)}2
Formally, the « same » molecules CrNi2
And slightly different properties …
Mn12(p-MeBz) Mn12(p-MeBz)H2O
Two Isomeric Mn12
D.N. Hendrickson, G. Christou et al.
Time necessary to relax 1% of MsatFe8
D > Fe8st > 57Fe8
0.1
1
10
100
1000
0 2 4 6 8 10
τ(s)
1/T (1/K)
Fe 8 with D
Fe 8 standard
Fe 8 with 57 Fe
from D. Gatteschi, R. Sessoli et al.
Exchange-biased quantum tunnelling in a supramolecular dimer of single-molecule magnets
W. Wernsdorfer, N. Aliaga-Alcalde, D. N. Hendrickson & G. ChristouNature 416, 406 (28 March 2002)
QuickTime™ et un décompresseurGraphique sont requis pour visualiser
cette image.
�S = 9/
�S = 9/
J
To get high spin and anisotropic
molecules :some work in progress
To get high spin and anisotropic molecules :some working directions
-I- Tetra or Hexanuclear Complexes CrNi3, CrNi5
-II- Anisotropic Ions Co(II), Mn(III)
-III- Heterotrimetallic Complexes CrNi2Mn4
-IV- Anisotropic Hearts
Octacyanometalates
Fe(II)(phen)(CN)4
Well insulated :-V- Dilution in a dia/paramagnetic matrix
CrNi2 in CoNi2-VI- Interaction with light
V. Marvaud
Synthetic Strategy I
Cr(III)Ni(II)3, Tetranuclear Complex, C3v axis
CrNi3, S=9/2
- Isostructural with CoNi3
Caracterisation :
- Mass Spectrometry : M = 1712.98
Magnetic Properties • Ferromagnetic Interaction
Hexagonal R 3a = b = 18,343 Å; c = 23,394 Å
V = 6818 Å3 , Z = 3
• S = 9/2
• J = +9.7�0 cm -1, D = -0.095 cm-1
• Hysteresis at 30 mK
V. Marvaud, F. Tuyèras
C3v
Using Anisotropic Ions, Co(II) and Mn(III) (large D)
Monoclinic C 2/ma = 17,821 Å; b = 14,275 Å; c = 8,602 Å
b = 99,206°;
Magnetic Properties
• Antiferromagnetic Interaction
• S = 5/2
• J , D in progress
Cr(III)Mn(III)2
Synthetic Strategy II
Cristallographic Structure
V. Marvaud, F. Tuyèras
Hetero tri metallic Complexes , Cr(III)Ni(II)2Mn(II)4
+
Trigonal R -3a = b = 23,26 Å; c = 20,35 Å
α = β = 90°; γ = 120°; V =9510 Å3
Synthesis Cristallographic Structure
NiII NiII MnIICrIII
Synthetic Strategy III
V. Marvaud, F. Tuyèras
S=1 S=3/2 S=1 S = 5/2
0
2
4
6
8
10
12
14
0 1 104 2 104 3 104 4 104 5 104 6 104 7 104
M (
MB
)
H / Gauss
CrNi2Mn4 : magnetic properties
S = (4 x 5/2) - 3/2 - (2 x 1) = 13/2
Cr-Ni FCr-Mn AF
22
24
26
28
30
32
34
36
0 50 100 150 200 250 300
Chi
*T
T(K)
Collaboration: R. Sessoli & D. Gatteschi
Hexagonal R -3a = b = 23,26 Å; c = 20,35 Åa = b= 90°; g = 120°; V =9510 Å3
V. Marvaud, F. Tuyèras
CrNi2Mn4 : High Field EPR
-0,003
-0,002
-0,001
0
0,001
0,002
0,003
0,004
8 8,5 9 9,5 10 10,5 11 11,5
inte
nsité
Champ
-0,004
-0,003
-0,002
-0,001
0
0,001
0,002
0,003
6 6,5 7 7,5 8 8,5 9 9,5 10
inte
nsité
champ
CrNi2 CrMn6
-0,002
-0,0015
-0,001
-0,0005
0
0,0005
0,001
0,0015
6,5 7 7,5 8 8,5 9 9,5 10
inte
nsité
Champ
CrNi2Mn4
Coll.A.L. Barra & D. Gatteschi
285 GHz10 K
230 GHz15 K
230 GHz15K
V. Marvaud, F. Tuyèras
CrNi2Mn4 : « Genio » Calculations
Collaboration: D. Gatteschi
CrNi2Mn4 CNi = 0,00833 CMn = 0,11096CCr = 0,025
D = ciDi
i∑ + cijDij
ij∑
V. Marvaud
Looking for the best Hetero-Tri-Metallic Systems
Cr{NiL}2 {NiL’}4 predicted to be a « Single Molecule Magnet »
Heterotrimetallic Complexes
+
+
CrNi2Mn4
CrNiMn5
And others !
V. Marvaud
CrNi4 …
2 - Bidendates TRANS 3 - Trisdendates FAC y MER
4 - Tetradendates CIS 6 - Hexadendates 8 - Octadendates
Synthetic Strategy IVAnisotropic “Hearts”
Monoclinic P 21/ na = 14,581 Å; b = 29,044 Å; c = 18,679 Å
b = 103,708°;
Fe(II)(phen)Cu(II)4
Fe(II), S = 0 !
Monoclinic P 21/ aa = 14,245 Å; b = 14,584 Å; c = 16,261 Å
b = 111,323°;
Fe(II)Cu(II)4
Ni(II) square planar, S = 0 !
Polynuclear Complexes with Anisotropic Hearts
Fe(III) reduced to Fe(II) …
Synthetic Strategy VDilution in a dia/paramagnetic matrix
CrNi2 diluted in a CoNi2 matrix
Cr(III) or Co(III)
NB : Co(III), d6, diamagnetic
-1
-0.5
0
0.5
1
-0.8 -0.4 0 0.4 0.8
0.04 K0.10 K0.12 K0.14 K
M/M
s
µ0 H (T)
dH/dt = 0.035 T/s
0
-0.2 -0.1 0 0.1 0.2
0.04 K0.10 K0.12 K0.14 K
M/M
s
µ0 H (T)
dH/dt = 0.035 T/s
CrNi2 diluted in a CoNi2 matrix
Sigmoïdal signal is from matrix • Quick Relaxation at H=0 ; • Steeper magnetisation rise at lower T
Hope : tunneling effect at H = 0 : SMM ?
WIVCuII6
MoIVCuII6
WIVNiII6MoIVNiII6
Monoclinic P na = 24.89 Å; b = 14,39 Å; c = 30,11 Å
a = g = 90°; b = 108.81°;
Monoclinic a = 22.03 Å; b = 28,39 Å; c = 22,01 Å
a = g = 90°; b =99.48°;
Monoclinic C ca = 25.39 Å; b = 15,22 Å; c = 30,72 Å
a = g = 90°; b = 111.45°;
WIVMnII6
MoIVMnII6
Heptanuclear Complexesfrom octacyanometalate precursors
V. Marvaud, J.M. Herrera, work in progress
WIVCuII6
MoIVCuII6
WIVNiII6MoIVNiII6
Monoclinic P na = 24.89 Å; b = 14,39 Å; c = 30,11 Å
a = g = 90°; b = 108.81°;
Monoclinic a = 22.03 Å; b = 28,39 Å; c = 22,01 Å
a = g = 90°; b =99.48°;
Monoclinic C ca = 25.39 Å; b = 15,22 Å; c = 30,72 Å
a = g = 90°; b = 111.45°;
WIVMnII6
MoIVMnII6
V. Marvaud, J.M. Herrera, work in progress
Synthetic Strategy VInteraction with light
Octacyanometalate Precursors
Heptanuclear Complexes
0.0012
0.0014
0.0016
0.0018
0.002
0.0022
Emu
Time (h.mn)
T = 10 KH = 20 kOe
0.00 2.00 4.00 6.00 8.00 10.00
Magnetisation (H=2T) at T= 10K as f(irradiation time)
MoIVCuII6 : photomagnetic molecule !
M / u.a.
Time / min.
Collaboration: C. Mathonière, ICMC Bordeaux
hν
6 x (S = 1/2) S = 3
Photo-excitation MoIVCu6 MoVCuII5CuI ?
MoIVCuII6 MoVCuI
1CuII5
MoV, d1 , S=1/2Ferro interaction …MoIV, d2 , S=0
No exchange6 isolated S=1/2
Photo-induced electron transfer
MoV CuI
+5
MoIV CuIIhν
+5
S=3
2
2.5
3
3.5
4
4.5
5
0 50 100 150 200 250 300
xT before hv
xT after hv
χ MT / emu mol
-1 K
T / K
χMT = f(T) before irradiation and after irradiation
MoIVCuII6
χ MT
before
afterhν
280 K
hν (405 nm), 19 h, 5 K
0
1
2
3
4
5
0 10000 20000 30000 40000 50000
simulationM after hvM before hvM after cycling T
M / N
β
Field / Oe
MoIVCuII6 : further data
Magnetisation vs H at T= 10K : Experiment and simulation
Fully reversible !
° Before irradiation-- After cycling at
Room T
• After irradiation-- Simulation (S=3)
• Introduction : molecular magnetism- the molecular approach to nanosystems
• What a chemist must & can control ?• From High Spin Molecules to SSM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets• Conclusions
Outline
Anisotropic precursor
[Fe(III)(bipy)(CN)4]-
R. Lescouëzec, M. Julve, Valencia, Spain D. Gatteschi, W. WernsdorferAngewandte Chem. 2003, 142, 1483-6
Feasibility of « Molecular nanowires » ?
2 [FeIII(bipy)(CN)4]- + [CoII(H2O)6]2+
FeIII, d5
bas spinS = 1/2
CoII, d7
haut spinS = 3/2
Anisotropic precursor(Structure)
Anisotropic assembler(Electronic Structure)
Bimetallic Chain ! [{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
Cristallographic Structure (along a axis)
MonoclinicP21/na =7,591Åb =15,190Åc =14,714Åß =92,92°
J. Vaissermann, Paris
Chain [{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
Perspective View
J. Vaissermann
7.59 Å (a)
Chain catena-µ- [{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H 2O]n
Few and Weak Interchains contacts
Chain catena µ- [{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H 2O]n
View down axis a
Observe the angle between chains
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
Magnetic Properties (powder)
5
10
15
20
25
30
0 50 100 150 200 250 300
χ MT
/ cm
3 mol
-1
T/K
Fe(bipy)(CN)4Co
poudre
0
10
20
30
40
50
60
0 50 100 150 200 250 300
Fe(bipy)(CN)4, poudre
1/χΜ
T / K
θ = +18.1 K
r = 0.99995 (30 < T < 300 K)
FERROMAGNETIC INTERACTION !
Orbital interpretation : Orthogonality of Magnetic orbitals
R. Lescouëzec, J. Cano
6
8
10
12
14
16
6 7 8 9 10 11 12 13
M / a. u.
T /
b
c
a
K
FCM plots along crystallographic axes a, b, c (H = 5000 Oe)
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
0.80
1.0
1.2
1.4
1.6
1.8
0 60 120 180 240 300
theo
exp
M / a. u.
α
b
c
/ deg
Magnetisation in the bc plane (H = 5000 Oe ; T = 5 K)
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
m1 m2
Mb
Mc
m1
m2
31o
59o
Scheme I
b
c
a
Co
FeOw
Magnetisation in the bc plane (H = 5000 Oe ; T = 5 K)
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
0.0
0.5
1.0
1.5
2.0
3 4 5 6 7 8
χ" / a. u.
T /
1000100
1010.1
Kχ‘‘ vs. T plots along the b axis.
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
Slow relaxation of the magnetisation !
Single crystal ac susceptibilityMeasurements(SQUID)
R. Lescouezec, F. Lloret
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
Magnetisation on microSQUID (microcrystal)
Hx
12°
-20°
-32°
Hyeasy axis
minor species
easy axismajor species
50 µm
crystal
W. Wernsdorfer, LLN Grenoble
-1
-0.5
0
0.5
1
-0.8 -0.4 0 0.4 0.8
0.070 T/s0.035 T/s0.017 T/s0.008 T/s0.004 T/s0.002 T/s0.001 T/s
M/M
sµ0 H (T)
2.0 KH || b
Slow relaxation of the magnetisation
Constant TemperatureVarying Sweeping Rates
MicroSQUID Single crystal measurements // b axis
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
W. Wernsdorfer, Grenoble
-1
-0.5
0
0.5
1
-1.2 -0.8 -0.4 0 0.4 0.8 1.2M
/Ms
µ0 H (T)
H || b
2.0 K
1.5 K
1.1 K
0.05 K0.002 T/s
7.0 K
W. Wernsdorfer, Grenoble
Constant Sweeping RateVarying Temperature
MicroSQUID Single crystal measurements // b axis
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2•�4H2O]n
Slow relaxation of the magnetisation
0
0.2
0.4
0.6
0.8
1
0.01 0.1 1 10 100 1000M
/Ms
t (s)
1.5 K
1.6 K
1.7 K
1.8 K
1.9 K
2.8 K
2.7 K
2.6 K
2.5 K 2.3 K
2.2 K
2.1 K
2.4 K
2.0 K
M vs. t plots along the b axis.
Both ac and dcmeasurementsindicate thermally activated relaxation of the magnetisation:
ac: Ea= 142 K, τ0 = 6.10-11 sdc: Ea= 43 K, τ0 = 2.10-8 s
The different values of τ0and Ea are attributed to different relaxation processes.
Slow relaxation of the magnetisation …
W. Wernsdorfer, Grenoble
Slow relaxation of the magnetisation in 1D …
1) New phenomenon See Gatteschi et al. Angewandte Chemie, 2001See Miyazaka, J. Am. Chem. Soc. 2002 and this conference
2) Ising slow relaxing chains can be viewed as 1D nanomagnets or nanowires (or single chain magnets) …
3) Prospects :- mechanisms of the magnetisation reversal - local origin of the anisotropy (CoII, FeIII, CoII-FeIII ?)- applications for information storage ?
A flexible chemical system Substitutions (pure or doped systems) :
• Co(II) by Zn(II) (dia)• Fe(III) by Co(III) (dia)
Co(II) / Zn(II)Fe(III) / Co(III)
Slow relaxation of the magnetisation in 1D …
4) Active field in progress … - Search for quantum tunneling in 1D …
-1
-0.5
0
0.5
1
0 0.2 0.4 0.6 0.8
M/M
s
µ 0 H (T)
2 K2.1 K
2.2 K2.3 K
2.4 K
2.0 K 1.9 K1.8 K
1.7 K
1.6 K
1.5 K
1.4 K1.3 K1.2 K
Is the regime becoming independentof temperature ?
• Introduction : molecular magnetism- the molecular approach to nanosystems
• What a chemist must & can control ?• From High Spin Molecules to SSM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets• Conclusions
Outline
• Introduction :• What a chemist must & can control ?• From High Spin Molecules to SSM
- a systematic, rational, approach- the photomagnetic way …
• Single Chain Magnets
• Conclusions and acknowledgements
Everything possiblein molecular magnetism ?
NO, but …• Molecular engineering• Molecules in the solid : molecular engineering • Subtleties in structures and electronic properties• But new exciting fields :
- multifunctional materials- molecular electronics ; quantum computing
• We did the easiest • The most exciting is coming, for young scientists …
Prospects (long term)• Magnetic storage on ONE single molecule
Prospects (short term)
• Improved Instrumentation (microSQUID + …)
• Quantum computing
• New chemical systems with larger ? E
Magnetic TipHSM "up" HSM "down"
Surface
Next « device » ?Recording on one molecule !
Exciting joint venture between physicists and chemiststheoreticians and experimentalists
Molecular Approach to Nanomagnets and Multifunctional Materials
D. Gatteschi, Florence
6ème PCRD, NOEProposal
Scientific exchanges …Scientific exchanges …
Fuji-san, November 17, 2002
q To increase and to share new knowledges
q To improve mutual knowledgeq scientific …q cultural …
q To better understand and respect each other
Science for peace …(V. Balzani, Seeheim 2001)
q To develop friendship and to protect peace
Hiroshima, November 23, 2002
Kyoto November 14, 2002, TofukuKyoto November 14, 2002, Tofuku--ji gardenji garden
AcknowledgementsAcknowledgementsMy coworkersMy coworkers
Research groups quotedResearch groups quoted
French Ministery of Higher EducationFrench Ministery of Higher Education
C.N.R.SC.N.R.S
Tokyo Institute of Technology ProfessorTokyo Institute of Technology Professor EnokiEnokiNagoya University ProfessoNagoya University Professor Awagar AwagaOrganizers of the meeting Professor Miyashita eOrganizers of the meeting Professor Miyashita et aliit alii
European TMR Molnanomag and M3D, ESFEuropean TMR Molnanomag and M3D, ESF
and YOUand YOU
for kindfor kindattentionattention
Kyoto November 2002Kyoto November 2002Imperial Palace GardenImperial Palace Garden
Work partly done in Pierre & Marie Curie University
Acknowledgements to my coworkers
ChristopheCartier ditMoulin
FrançoiseVillain
AnneBleuzen
CyrilleTrain
Cédric Desplanches,Natividad Galvez, Ricardo Moroni, Raquel Garde
Virginie Escax, Juan Manuel Herrera, Fabrice PointillartFabien Tuyèras, Guillaume Champion, Mannan Seuleiman, Hayat Hanouti
V. GadetS. Ferlay
A. ScuillerR. Lescouëzec
ValérieMarvaud
Dante GatteschiChaire Blaise Pascal 2001
