摘要 : Title complexes have been synthesised on reacting 1-ethyl-2-(arylazo)imidazoles (RL, where R = H, Me, Ome, Cl) with (NH_4)_2[OsCL_6]. Two isomers, blue-violet (isomer-A) and redviolet (isomer-B) of the composition OsCl_2(RL)_2 hav... 展开 Title complexes have been synthesised on reacting 1-ethyl-2-(arylazo)imidazoles (RL, where R = H, Me, Ome, Cl) with (NH_4)_2[OsCL_6]. Two isomers, blue-violet (isomer-A) and redviolet (isomer-B) of the composition OsCl_2(RL)_2 have been chromatographically separated. IR spectra show the presence of two v(Os-Cl) (300-310 and 320-330 cm~(-1)) and suggest the complexes with cis-OsCl_2 configuration. Three geometrical isomers with cis-OsCl_2 configuration are possible; with consideration of co-ordination pairs in the order of Cl, N [N(imidazole)] and N'[N(azo)] they are cis-tans-cis (ctc), cis-cis-trans (cct) and cis-cis-cis (ccc). The ~1H-NMR spectra identify isomer-A and isomer-B as ctc- and ccc- configurations, respectively. Absorption spectra exhibit multiple MLCT [t_2(Os)->#pi#~*(RL)] transitions in the visible region and the energy of transition follows the order ccc > ctc. Redox studies show Os(III)/Os(II) and Os(IV)/Os(III) couples at 0.4-0.6V and 1.6-1.7 V versus SCE, respectively along with ligand reductions. 收起