Syntheses, crystallography and spectroelectrochemical studies of ruthenium azomethine complexes

Three novel families of azomethine ligands L of the type C6H5N=NC(COCH3)=N(4-YC6H4) (6), C6H5N=NC(CO2CH3)=N(4-YC6H4) (7) and 4-ClC6H4N=NC(CO2CH3)=N(4-YC6H4) (8), [Y=H (a), CH3 (b), Cl (c), Br (d), C10H7 (e), OCH3 (f), NO2 (g)] have been synthesized and reacted consecutively with RuCl3, 2,2'-bipyridine (bpy) and lithium chloride in ethanol under refluxing conditions to produce three novel families of trans-[Ru-II(bpy)LCl2] complexes. These complexes were characterized by elemental analysis, IR, H-1 NMR, UV-Vis spectroscopy and cyclic voltammetry. Crystallographic studies of two ruthenium(II) azomethine complexes (13 and 18) show that the Ru(II) ion occupies a distorted octahedral coordination sphere in which the chloride ligands are trans to each other and the azomethine and bipyridine nitrogen donor atoms are equatorially coordinated. Crystallographic, electrochemical, electronic spectral data and time-dependent DFT calculations are all consistent with azomethine ligands possessing strong pi-acceptor properties. These pi-acceptor properties can be "tuned" by a judicious choice of substituents on the azomethine ligand. (c) 2007 Elsevier Ltd. All rights reserved.