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

Abstract

Silver-assisted aquation of blue cis-trans-cis-RuCl2(RAaiR’)2 (I) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH2)2(RAaiR’)2](ClO4)2 (II), where RAaiR’ = p-R-C6H4-N=N-C3H2-NN, abbreviated as N,N′ chelator (N(imidazole) and N(azo) represent N and N′, respectively); R = H (a), p-Me (b), p-Cl(c); R′ = Me (III), Et (IV), Bz (V), that reacted with NCS− in warm EtOH resulting in red-violet dithiocyanato complexes of the type [Ru(NCS)2(RAaiR)2] (IIIa–Vn). These complexes were studied by elemental analysis, UV-Vis, IR, and 1H NMR spectroscopy and cyclic voltammetry. The solution structure and stereoretentive transformation in each step have been established from 1H NMR results. All the complexes exhibit strong MLCT transitions in the visible region. They are redox active and display one metal-centered oxidation and successive ligand-based reductions. Linkage isomerisation was studied by changing the solvent and then by UV-Vis spectral analysis.