Ruthenium azo complexes: Synthesis, spectra and electrochemistry of dithiocyanatobis-{1-(alkyl)-2-(arylazo)imidazole}ruthenium(II)

Silver assisted aquation of blue cis-trans-cis-RuCl2 (RaaiR´)2 (1) leads to the synthesis of solvento species, blue-violet cis-transcis-[Ru(OH2)2(RaaiR´)2](ClO4)2 [RaaiR = p-R-C6H4-N=N-C3H2-NN, (2), abbreviated as N,N/-chelator, where N(imidazole) and N(azo) represent N and N/, respectively; R = H (a), p-Me (b), p-Cl (c) that have been reacted with NCS− in warm EtOH resulting in red-violet dithiocyanato complexes of the type, [Ru(NCS)2(RaaR)2] (3-5). The solution structure and stereoretentive transformation in each step have been established from 1H n.m.r. results. All the complexes exhibit strong MLCT transitions in the visible region. They are redox active and display one metal-centred oxidation and successive ligand-based reductions. Linkage isomerisation was studied by changing the solvent and then UV-Vis spectral analysis.