Ruthenium(II) bipyridine complexes bearing quinoline-azoimine (NN′N") tridentate ligands: Synthesis, spectral characterization, electrochemical properties and single-crystal X-ray structure analysis

Four octahedral ruthenium(II) azoimine-quinoline complexes having the general molecular formula [Ru-parallel to(L-Y)(bpy)Cl](PF6) {L-Y = YC6H4N=NC(COCH3)=NC9H6N, Y = H (1), CH3 (2), Br (3), NO2 (4) and bpy = 2,2'-bipyrdine} were synthesized. The azoimine-quinoline based ligands behave as NN'N '' tridentate donors and coordinated to ruthenium via azo-N', imine-N' and quinolone-N '' nitrogen atoms. The composition of the complexes has been established by elemental analysis, spectral methods (FT-IR, electronic, H-1 NMR, UV/Vis and electrochemical (cyclic voltammetry) techniques. The crystal structure of complex 1 is reported. The Ru(II) oxidation state is greatly stabilized by the novel tridentate ligands, showing Ru(III/II) couples ranging from 0.93-1.27 V vs. Cp2Fe/Cp2Fe+. The absorption spectrum of 1 in dichloromethane was modeled by time-dependent density functional theory (TD-DFT). (C) 2014 Elsevier B.V. All rights reserved.