Synthesis,structure and electrochemical properties of some thiosemicarbazone complexes of iridium |
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| Authors: | Semanti Basu Rama Acharyya William S Sheldrick Heike Mayer-Figge Samaresh Bhattacharya |
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| Institution: | (1) Inorganic Chemistry Section, Department of Chemistry, Jadavpur University, Kolkata, 700 032, India;(2) Lehrstuhl Fur Analytische Chemie, Ruhr Universitat Bochum, D-44780 Bochum, Germany |
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| Abstract: | Reaction of thiosemicarbazones of salicylaldehyde and 2-hydroxyacetophenone (H2L1 and H2L2) with Ir(PPh3)3Cl] affords complexes of type Ir(PPh3)2(L)(H)] (L = L1 or L2) in ethanol. A similar reaction carried out in toluene affords the Ir(PPh3)2(L)(H)] complexes along with complexes of type Ir(PPh3)2(L)Cl], where a chloride is coordinated to iridium instead of the hydride. The structure of the Ir(PPh3)2(L2)(H)] and Ir(PPh3)2(L2)Cl] complexes has been determined by X-ray crystallography. Crystal data for Ir(PPh3)2(L2)(H)]: space group, P21/c; crystal system, monoclinic; a=12.110(2) Å, b=17.983(4) Å, c=18.437(4) Å, β=103.42(3)°, Z=4; R 1=0.0591, wR 2=0.1107. Crystal data for Ir(PPh3)2(L2)Cl]: space group, P21/c; crystal system, monoclinic; a=17.9374(11) Å, b=19.2570(10) Å, c=24.9135(16) Å, β=108.145(5)°, Z=4; R 1=0.0463, wR 2=0.0901. In all the complexes the thiosemicarbazones are coordinated to the metal center as dianionic tridentate O, N, S-donors and the two triphenylphosphines are trans. The complexes are diamagnetic (low-spin d? 6, S=0) and show intense MLCT transitions in the visible region. Cyclic voltammetry on all the Ir(PPh3)2(L)(H)] and Ir(PPh3)2(L)Cl] complexes shows a quasi-reversible Ir(III)–Ir(IV) oxidation within 0.55–0.78 V vs. SCE followed by an irreversible oxidation of the thiosemicarbazone within 0.91–1.27 V vs. SCE. An irreversible reduction of the thiosemicarbazone is also observed within ?1.10 to ?1.23 V vs. SCE. |
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| Keywords: | Thiosemicarbazones of salicylaldehyde and 2-hydroxyacetophenone Iridium complexes Structure Spectral and electrochemical properties |
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