Transition metal quinone-thiosemicarbazone complexes 3: Spectroscopic characterizations of spin-mixed iron (III) of naphthoquinone-thiosemicarbazones |
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Authors: | Chikate Rajeev C Padhye Subhash B |
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Institution: | Department of Chemistry, University of Pune, Pune 411 007, India. rajuchikate@rediffmail.com |
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Abstract: | An interesting series of iron (III) complexes with naphthoquinone-thiosemicarbazones are synthesized and physico-chemically characterized by elemental analysis, UV-vis, IR, EPR and magnetic susceptibility measurements. They possess a cationic octahedral FeL2]+ species and a tetrahedral FeCl4]- anion and exhibit unusual spin-mixed states involving high-spin and low-spin ferric centers as revealed from magnetic behavior with significant amount of exchange interactions mediated by intermolecular associations. The magnetic susceptibility data is fitted with S1=5/2 and S2=1/2 Heisengberg's exchange coupled model; H=-2JS1S2 and the magnetic exchange interactions are found to be of the order of -13.6 cm-1 indicating the moderate coupling between two paramagnetic centers present in different chemical and structural environment. The presence of spin-paired iron (III) cation having dxz2dxz2dxz1 ground state is revealed from the EPR spectra with three prominent peaks while the high-spin tetrahedral iron (III) anion exhibits characteristics g=4 signal whose intensity increases with lowering the temperature suggesting its influence on the magnetic properties of the complex molecule. FTIR measurements indicate tridentate ONS donor systems involving quinone/hydroxyl oxygen, imine/hydrazinic nitrogen and thione/thiol sulfur atoms as binding sites for naphthoquinone-thiosemicarbazones. |
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Keywords: | Thiosemicarbazone Naphthoquinones Iron (III) complexes Spin-mixed complexes Magnetism ESR IR |
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