Photochemical reactions of trans-[Ru(NH3)4L(NO)]3+ complexes

The photochemical behavior of a series of trans-[Ru(NH3)(4)L(NO)](3-) complexes. where L = nitrogen bound imidazole. L-histidine, 4-picoline, pyridine, nicotinamide, pyrazine, 4-acetylpyridine. or triethylphosphite is reported. In addition to ligand localized absorption bands (<300 nm). the electronic spectra of these complexes are dominated by relatively low intensity bands assigned as ligand field (LF) and metal to ligand (d(pi) --> NO) charge transfer (MLCT) transitions. Irradiation of aqueous Solutions of these complexes with near-UV light (300-370 nm) labilizes NO. i.e., trans-[RU(NH3)(4)L(NO)](3+) -->(hx) [Ru(NH3)(4)L(HO)](3-) + NO Quantum yields for [Ru(NH3)(4)L(H2O)](3-) formation (phi(Ru(III))) are sensitive to the natures of L, lambda(irr) and pH. The lowest quantum yields (lambda(irr) = 310 nm) were found for L = imidazole (0.03) and L-histidine (0.04). while much higher values were found for L-P(OEt)(3) (0.30). irradiation at longer wavelengths does not induce photochemical reactivity. These results are interpreted in terms of the expected reactivities of d(pi) --> NO MLCT state in these systems. (C) 2003 Elsevier B.V. All rights reserved.