Structural and spectroscopic properties of Ru(II) complexes of 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde

Naskar, S., Naskar, S., Drew, M.G.B., Gorelsky, S.I., Lassalle-Kaiser, B., Aukauloo, A., Mishra, D. and Chattopadhyay, S.K. (2009) Structural and spectroscopic properties of Ru(II) complexes of 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde. Polyhedron, 28 (18). pp. 4101-4109. ISSN 0277-5387 doi: 10.1016/j.poly.2009.09.030

Abstract/Summary

Six Ru(II) complexes of formula [Ru(L)(2)(PPh3)(2)] have been prepared where LH = 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde. X-ray crystal structures of five of the complexes are reported. In all the complexes ruthenium is six coordinate with a distorted octahedral cis-P-2, cis-N-2, trans-S-2 donor environment, and each of the two thiosemicarbazone ligands are coordinated in a bidentate fashion forming a four membered chelate ring. The complexes undergo a one-electron oxidation at similar to 0.5 V vs. Ag/AgCl. The EPR spectrum of the electrochemically oxidized solution at 100 K shows a rhombic signal, with transitions at g(1) = 2.27, g(2) = 2.00 and g(3) = 1.80. DFT calculations on one of the complexes suggest that there is 35% ruthenium and 17% sulfur orbital contribution to the HOMO. These results suggest that the assignment of metal atom oxidation states in these compounds is not unambiguous. (C) 2009 Elsevier Ltd. All rights reserved.