Transient absorption and time-resolved Raman study of the photophysics of 4-phenylpyridine in solution

Authors:

• G. Buntinx,
• Ryszard Naskręcki,
• C. Didierjean,
• O. Poizat

Abstract

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 T₁ and S₁ 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 S₁ and T₁ 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 S₁ and T₁ 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.