RUTHENIUM COMPLEXES WITH 1,4,5,8-TETRAAZAPHENANTHRENE - UNUSUAL PHOTOPHYSICAL BEHAVIOR OF THE TRIS-HOMOLEPTIC COMPOUND

The photophysical and electrochemical properties of the series of complexes Ru(bpy)n(tap)3-n2+ (n = 0−3) (bpy = 2,2′-bipyridine; tap = 1,4,5,8-tetraazaphenanthrene) have been examined and compared with those of the other previously studied series. Although the mixed-ligand complexes seem to follow the same sequence of photophysical behaviors described in the literature for other series, the homoleptic Ru(tap)32+ presents peculiar properties; it is the only one whose emission lifetime does not seem to be controlled by the nonradiative deactivation from the 3MLCT (metal-to-ligand-charge-transfer triplet), but by the intersystem crossing to the 3MC (metal-centered triplet) state, responsible for the photolability of the complex. The luminescence quenching by Cl− ions and the emission lifetimes as a function of temperature, in absence and presence of Cl−, suggest that there would be a dynamic coupling of the 3MLCT with the 3MC through a rapid equilibrium between those states, at least in acetonitrile. © 1990, American Chemical Society. All rights reserved.