Synthesis, spectroscopic characterization, electrochemical and photochemical properties of ruthenium(II) polypyridyl complexes with a tertiary amine ligand

A series of ruthenium(11) polypyridine complexes were synthesized with a tertiary aliphatic amine ligand, [Ru(4,4'-X(2)bpy)(2)(DMAEPy)](2+) 1a: X=H, 2, X=CF3), [Ru(tpy)(N-N)Cl](+)- (3a: N-N = DMAEPy, 3c, N-N =DEAEPy) and [Ru(tpy)(DMAEPy)(MeCN)](2+) (4) where DMAEPy = 2-(2'-dimethlaminoethyl)-pyridine. DEAEP,=2-(2'-diethylaminoethyl)pyridine. tpy = 2,2':6',2"-terpyridine and bpy = 2.2'-bipyridine. The spectroscopic, electrochemical and photochemical properties of these complexes are studied and compared to those of the corresponding primary-amine complexes [Ru(bpy)(2)(AEPy)](2+) (1b) and [Ru(tpy)(AEPy)Cl](+) (3b) where AEPy = 2-(2'-aminoethyl)-pyridine. The MLCT bands in the UV-Vis absorption spectra of the tertiary-amine complexes were blue-shifted (8-9 nm), and their redox potentials for the Ru-II (III) couples were more positive than expected (90-100 meV) compared to the corresponding primary-amine complexes. Irradiation of an acetonitrile solution of the complexes causes selective photochemical ligand substitution of the tertiary-amine ligand even under aerated conditions, giving the corresponding solvento complex [Ru(4,4'-X(2)bpy)(2)(MeCN)(2)](2+) or [Ru(tpy)(MeCN)(2)Cl](+). (C) 2002 Elsevier Science Ltd. All rights reserved.