Abstract
Five octahedral ruthenium(II) complexes with azoimine-quinoline (Azo) and alpha-diimine (L) ligands having the general formula [Ru-II(L)(Azo)Cl](PF6) (1-5) {Azo: PhN=NC(COMe)=NC9H6N, L = 4,4'-dimethoxy-2,2'-bipyridine (dmeb) (1), 4,4'-di-tertbutyl-2,2'-bipyridine (dtb) (2), 1,10-phenanthroline (phen) (3), 5-chlorophenanthroline (Clphen) (4), or 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) (5)} were prepared by stepwise addition of the tridentate azoimine (H(2)Azo) and alpha-diimine (L) pro-ligands to RuCl3 in refluxing EtOH. The tridentate azoimine-quinoline ligands coordinate to ruthenium via the Azo-N', N'-imine and NaEuro(3)-quinolone nitrogen atoms. The spectroscopic properties (IR, UV/Vis, H-1, C-13 and F-19 NMR) and electrochemical behavior of complexes 1-5 and the X-ray crystal structures of complexes 2 and 3 are presented. The coordination of Ru(II) to these strong pi-acceptor ligands (Azo and L) results in a large anodic shift for the Ru(III/II) couples of 1.63-1.72 V versus NHE. The electronic spectra in MeCN and IR spectra in CH2Cl2 for complex 3 in its oxidized 3 (+) and reduced 3 (-) forms were investigated. The calculated absorption spectrum of 3 in MeCN was used to assign the UV-Vis absorption bands.