The transient absorption spectra and time-resolved resonance Raman spectra of 4-phenylpyridine (4PPY) in various organic solvents have been measured following pulsed photolysis at 266 nm using nanosecond and picosecond time resolution experiments. The T 1 and S 1 states are characterized and attributed to ππ* and nπ* configurations, respectively, in aprotic solvents as well as in alcohols and water. In the presence of alcohols, both the S 1 and T 1 states are reduced to the same transient product, the N -hydro radical 4PPYH • . The overall photophysical properties of 4PPY appear similar to those previously found for the diaza analogue, 4,4‘-bipyridine. Vibrational analyses of the S 1 and T 1 states and of the radical 4PPYH • are proposed and compared with results reported in the literature for the neighboring compounds biphenyl and 4,4‘-bipyridine. The structure and electronic configuration of these transients are discussed on this basis.
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Buntinx et al. (1997) studied this question.