Indian Journal of Chemistry Vol. 24A, November 1985, pp. 942-945 Thermal, Spectral & Magnetic Studies of Complexes of Co(II), Ni(II), Cu(II), Zn(II) & Cd(II) with Substituted Cha1cones T SEETHARAMA RAO, K LAXMA REDDY, S J SWAMY & P LINGAIAH* Department of Chemistry, Kakatiya University, Warangal 506009 Received 10 May 1985, revised and accepted 24 June 1985 Complexes ofCo(II), Ni(ll), Cu(II), Zn(I1) and Cd(I1)with 3-{2-furyl)-1-{2' -hydroxyphenyl)-2-propen-l-one (FHPO), 3-{2- furyl)-1-{2' -hydroxy-5' -methylphenyl)-2-propen-l-one (FHMPO) and 3-{2-thienyl)-1-{2' -hydroxyphenyl)-2-propen-l-one (THPO) have been synthesized and characterized by analytical, conductivity, thermal, magnetic and infrared, electronic and ESR spectra data. Based on analytical and thermal data, the stoichiometry of the complexes has been found to be 1:2(metal: ligand). The infrared spectral data of the metal complexes indicate that FHPO, FHMPO and THPO act as mononegative tridentate towards Co(ll) and Ni(II) and bidentate towards Cu(ll), Zn(II) and Cd(II) metal ions. The electronic spectral data suggest that all the Co(ll) and Ni(II) complexes are octahedral, whereas Cu(I1)complexes are square-planar. The complexes of Zn(I1)and Cd(ll) are tetrahedral. Various ligand field parameters of Co(I1)and Ni(II) complexes and ESR parameters of Cu(II) complexes have been calculated. Chalcones usually exhibit germicidal", bactericidal>, fungicidal> and carcinogenic- activities. o-Hydroxy- chalcones have been used as analytical reagents in the estimation of different metal ions 5, and these also act as mononegative bidentate ligands towards Cu(II), Ni(II) and Co(IIf·7. This aroused our interest to investigate the nature of the metal-ligand bond in the complexes of chalcones having furan or thiophene ring in place of phenyl ring in o-hydroxychalcones. The present paper deals with the preparation of complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(JI) with 3-(2-furyl)-I-(2' -hydroxyphenyl)-2-pro- pen-l-one (FHPO), 3-(2-furyl)-I-(2' -hydroxy-5- methyl-phenyl)-2-propen-I-one (FHMPO) and 3-(2- thienyl)-I-(2' -h ydroxyphenyl)-2-propen -I-one (THPO) and their characterization based on analytical, conductivity, thermal, magnetic and infrared, electronic and ESR spectral data. Materials and Methods All the chemicals used were of AR grade. The ligands were prepared as reported in literature'" and their purities checked by TLC and melting point determinations. Preparation of complexes The following general procedure was adopted for the preparation of all the complexes. Metal salt solution (30 ml) in methanol was added dropwise to a solution (60 ml) of the ligand in methanol with con- stant stirring. In all the cases the ligand concentration was kept in slight excess over the 1:3 metal-ligand molar ratio. The reaction mixture was refluxed on a water-bath for 60-90 min, cooled, the solid obtained filtered and washed several times with hot water and 942 methanol until the washings were free from the excess ligand. These complexes were finally dried in vacuo over fused calcium chloride. Physical measurements Molar conductivities of the complexes in DMF were measured using Digisun digital conductivity meter, model DI-909. Magnetic susceptibilities were mea- sured at room temperature by Guoy method using Hg[Co(NSC) 4] as the cali brant. Diamagnetic cor- rections were applied using Pascal's constants. Ther- mal data of the complexes were obtained using a Stanton thermo balance. Infrared spectra of the ligands and the complexes in the region 4000-200cm -1 were recorded in nujol on a Perkin-Elmer infrared spectro- photometer model-283, electronic spectra of the com- plexes in DMF on a Shimadzu multipurpose recording spectrophotometer model MPS-5000, and the solid state ESR spectra of Cu(II) complexes at room temperature on a Varian E-M, X-band instrument. Results and Discussion All the complexes are stable at room temperature, non-hygroscopic, insoluble in water and many of the common organic solvents, but soluble slightly in acetone, and freely in DMF and DMSO. The analyti- cal data of the complexes (Table!) indicate that the metal to ligand ratio is 1:2. The molar conductances of 1 x 10 -3M solutions of the complexes in DMF are in the range 6- 120hm -lcm2mol-l, indicating their non-ionic na- ture 10. Thermal study All the complexes are thermally stable upto 250°C
Transcript
Indian Journal of ChemistryVol. 24A, November 1985, pp. 942-945
Thermal, Spectral & Magnetic Studies of Complexes of Co(II), Ni(II),Cu(II), Zn(II) & Cd(II) with Substituted Cha1cones
T SEETHARAMA RAO, K LAXMA REDDY, S J SWAMY & P LINGAIAH*Department of Chemistry, Kakatiya University, Warangal 506009
Received 10 May 1985, revised and accepted 24 June 1985
Complexes ofCo(II), Ni(ll), Cu(II), Zn(I1)and Cd(I1)with 3-{2-furyl)-1-{2'-hydroxyphenyl)-2-propen-l-one (FHPO), 3-{2-furyl)-1-{2'-hydroxy-5' -methylphenyl)-2-propen-l-one (FHMPO) and 3-{2-thienyl)-1-{2'-hydroxyphenyl)-2-propen-l-one(THPO) have been synthesized and characterized by analytical, conductivity, thermal, magnetic and infrared, electronic andESR spectra data. Based on analytical and thermal data, the stoichiometry of the complexes has been found to be 1:2(metal:ligand). The infrared spectral data of the metal complexes indicate that FHPO, FHMPO and THPO act as mononegativetridentate towards Co(ll) and Ni(II) and bidentate towards Cu(ll), Zn(II) and Cd(II) metal ions. The electronic spectral datasuggest that all the Co(ll) and Ni(II) complexes are octahedral, whereas Cu(I1)complexes are square-planar. The complexes ofZn(I1)and Cd(ll) are tetrahedral. Various ligand field parameters of Co(I1)and Ni(II) complexes and ESR parameters of Cu(II)complexes have been calculated.
Chalcones usually exhibit germicidal", bactericidal>,fungicidal> and carcinogenic- activities. o-Hydroxy-chalcones have been used as analytical reagents in theestimation of different metal ions 5, and these also actas mononegative bidentate ligands towards Cu(II),Ni(II) and Co(IIf·7. This aroused our interest toinvestigate the nature of the metal-ligand bond in thecomplexes of chalcones having furan or thiophenering in place of phenyl ring in o-hydroxychalcones.The present paper deals with the preparation ofcomplexes of Co(II), Ni(II), Cu(II), Zn(II) andCd(JI) with 3-(2-furyl)-I-(2' -hydroxyphenyl)-2-pro-pen-l-one (FHPO), 3-(2-furyl)-I-(2' -hydroxy-5-methyl-phenyl)-2-propen-I-one (FHMPO) and 3-(2-thienyl)-I-(2' -h ydroxyphenyl)-2-propen -I-one(THPO) and their characterization based onanalytical, conductivity, thermal, magnetic andinfrared, electronic and ESR spectral data.
Materials and MethodsAll the chemicals used were of AR grade. The
ligands were prepared as reported in literature'" andtheir purities checked by TLC and melting pointdeterminations.
Preparation of complexesThe following general procedure was adopted for
the preparation of all the complexes. Metal saltsolution (30 ml) in methanol was added dropwise to asolution (60 ml) of the ligand in methanol with con-stant stirring. In all the cases the ligand concentrationwas kept in slight excess over the 1:3 metal-ligandmolar ratio. The reaction mixture was refluxed on awater-bath for 60-90 min, cooled, the solid obtainedfiltered and washed several times with hot water and
942
methanol until the washings were free from the excessligand. These complexes were finally dried in vacuoover fused calcium chloride.
Physical measurementsMolar conductivities of the complexes in DMF were
measured using Digisun digital conductivity meter,model DI-909. Magnetic susceptibilities were mea-sured at room temperature by Guoy method usingHg[Co(NSC) 4] as the cali brant. Diamagnetic cor-rections were applied using Pascal's constants. Ther-mal data of the complexes were obtained using aStanton thermo balance. Infrared spectra of the ligandsand the complexes in the region 4000-200cm -1 wererecorded in nujol on a Perkin-Elmer infrared spectro-photometer model-283, electronic spectra of the com-plexes in DMF on a Shimadzu multipurpose recordingspectrophotometer model MPS-5000, and the solidstate ESR spectra of Cu(II) complexes at roomtemperature on a Varian E-M, X-band instrument.
Results and DiscussionAll the complexes are stable at room temperature,
non-hygroscopic, insoluble in water and many of thecommon organic solvents, but soluble slightly inacetone, and freely in DMF and DMSO. The analyti-cal data of the complexes (Table!) indicate that themetal to ligand ratio is 1:2.
The molar conductances of 1 x 10 -3M solutions ofthe complexes in DMF are in the range 6-120hm -lcm2mol-l, indicating their non-ionic na-ture 10.
Thermal studyAll the complexes are thermally stable upto 250°C
RAO et af.: COMPLEXES OF Co(In, Ni(ID, Cu(II), Zn(In & Cd(ID WITH CHALCONES
Tabl Mahendra IC-4572 table
Tablel-Analytieal and Far Infrared Data (in em -1) of the CompoundsCompound Found (calc) % \o(M-O) \o(M-S)
indicating the absence of coordinated water or water ofcrystallization. All the complexes decompose in asingle step in the range 250-400°C corresponding to theloss of ligand moieties. The final product of decom-position as computed from the TG curves correspond,in each case, to metallic oxide. The decomposition israpid in the beginning but slow in the final stages. Thesharp decomposition observed in the case of chelatesof Cu(IJ) with several phenolic oximes 11 is not seen inthese complexes. This may be due to the difference inthe coordination sites (oxygen in the case of chalconesand more basic nitrogen in the case of oximes) of thesetwo types of ligands. The complexes are thermallystable to varying degrees. Taking the decompositiontemperatures of the complexes as a measure of their
thermal stability, the order of Jigands that form stablecomplexes is THPO <FHPO <FHMPO. The relativeorder of stabilities observed in the present complexesmay be explained in terms of increase in the number ofmetal-oxygen bonds through z-electron delocali-zation 12.
Infrared spectraIn the IR spectra of all the Jigands an intense band at
1630 em -1 is attributed to v(C =0)13. This bandis shifted to lower wavenumbers (Av == 40 em -I) in thespectra of the complexes indicating coordination th-rough oxygen ofC=O groupl3. The medium intensityband appearing around 1570 em -I in the Jigands andthe complexes are assigned to I'C = C (aroma tic). The
943
INDIAN J. CHEM., VOL. 24A, NOVEMBER 1985
free ligand bands in the region 1330-1370 cm -I due to0-H deformation mode are not present in the spectraof the metal complexes indicating complex formationby deprotonation ofO-H 14. The ligands FHPO andFHMPO exhibit a band at 1280cm -I which can beassigned to J>(C-0) of furan ring. This band is shiftedto lower wavenumbers (~v=50cm -I) in the spectraof complexes of Co(Il) and Ni(ll) indicating coordi-nation of oxygen of the furan ring!". The v(C-S) inTHPO appearing at 1150cm -I is shifted to lowerwavenumbers (~v=30cm -I) in the complexes DfCo(II) and Ni(H) indicating participation of sulphur ofthe thiophene ring in coordination 16.
Thus it is clear from the IR data that the ligandsFHPO, FHMPO and THPO act as mononegativetridentate towards Co(II) and Ni(II) and bidentatetowards Cu(II), Zn(H) and Cd(Il). The participationof oxygen and sulphur [the latter only in the case ofcomplexes ofTHPO with Co(Il) and Ni(II) 1 is furthersupported'I-" by the appearance of v(M - 0) at 500and 470 and v(M-S) at 310cm -I.
Electronic spectraAll the ligands exhibit strong bands around
36000 em -I with a shoulder at 34000 em -I, assignableto rr*<-rr and rr*<-n transitions respectively. Elec-tronic spectra of Co(l I) complexes display three bandsaround 8200, 17000 and 19500 em -I which may beassigned to the spin-allowed transitions 4T2g(F)<-4T1iFf....I'I); 4A2iF)<-4T1iFf....v2) and 4T1g(P)<-47;g (F)(v:J respectively, characteristic of octahedralgeometry around Co(II) I 7. The octahedral geometryof Co (II) complexes is further supported by the ratio ofv)v I which lies in the range 2.05 to 2.09 (ref. 19).
Electronic spectra of Ni(II) complexes exhibitthree bands around 8900, 14900 and 25200 cm -I whichmay be assigned to the transitions 3T2g(F)<-3A2g(F)(VI); 3 T1iF)<-3A2g(F)(V2) and 3TIg(P)<-3A2iFf....v3) respectively. These are in consonance '"with the octahedral geometry around Ni(II). The
values ofv2/vl which lie in the range 1.62-1.66, provideadditional support to this observation 17.
Various ligand field parameters, such as the ligandfield splitting energy (lODq), Racah inter-electronicrepulsion parameter (E), covalent factor (p) and LFSEhave been calculated for all the Co(Il) and Ni(II)complexes/" (see Table 2). The calculated 10Dq valuesof Co(ll) and Ni(ll) complexes suggest for theseligands a place between water and ammonia in thespectrochemical series. The B-values for the complexesare lower than the free ion value, thereby indicatingorbital overlap and delocalisation of d-orbitals. The fJ-values obtained are less than unity suggesting con-siderable amount of covalent character of the metal-ligand bonds.
The electronic spectra of Cu(II) complexes exhibitstrong bands around 15000 and 20000cm -I whichmay be assigned to 2B2g<-2BIg and 2Eg<-2BIg transi-tions, respectively, characteristic of square-planar geo-metry+'.
Magnetic momentsThe experimental and calculated magnetic moments
of the complexes are given in Table 2. The valuesobtained for the complexes ofCo(II), and Ni(II) are inthe ranges expected for octahedral geometry'-". Thecalculated magnetic moments also lie in this range. Allthe Cu(II) complexes possess magnetic moments cor-responding to one unpaired electron. Zn(II) and Cd(II)complexes are diamagnetic. Tetrahedral geometry isthe most preferred structure for the tetra-coordinatedZn(II) and Cd(II) complexes.
ESR studyThe ESR spectra of eu(II) complexes in the polyc-
rystalline state show two peaks, one of intense absor-ption at high field and the other of less intensity at lowfield. From these spectra the values of gll and gl havebeen calculated and are given in Table 3. The observedg-values point to the presence of the unpaired electron
Complex
Table2-Magnetic and Ligand Field Parameters of Complexes
RAO et al.: COMPLEXES OF cerm, Ni(In, Cu(In, zean & cerm WITH CHALCONES
Table3-ESR Data of Cu(II) Complexes[Cu(FHPO)21 [Cu(FHMPO)21ESR spectral
parametergll
,+G
alpha (a2)a'2
2.252.062.194.300.570.350.981.050.560.60495
beta (fJ)gamma (y)
~1lambda (),,)
[Cu(THPO)21
2.202.052.104.150.560.360.830.980.470.55383
2.232.062.124.000.670.250.800.980.530.66444
in the dX2_y2 orbital with gll>gl characteristic ofsquare-planar or elongated tetragonal geometry. Thegll obtained for the Cu(II) complexes is less than 2.3indicating covalent character of the metal-ligandbond 2 4. The axial symmetry parameter (G) for thecomplexes is found to be greater than 4 (Table 3). Thisshows absence of interaction between copper centres inthe solid state+'.
Further, orbital parameters rlr r1 (l2, (l'2, Y and Ahave been calculated (Table 3). The (X2 values for thepresent complexes fall in the range 0.4-0.6, indicatingappreciable in-plane covalency. As rp' rn in all thecomplexes, this indicates that the ligands are in-planen-bonded 26. The spin-orbit coupling constant for thecomplexes is found to be less than that of the free metalion (~o = - 828em -1), suggesting considerable mix-ing of ground and excited terms. The g-values are alsouseful for calculating the magnetic moment (p.)of thecomplexes and the calculated values are in goodagreement with the experimental ones (Table 2).
AcknowledgementTwo of the authors (TSR and KLR) are grateful to
the UGC and the CSIR, New Delhi respectively forfinancial assistance.
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