Asymmetric structure for the excited S-1 state of 2,2 '-bipyridine evidenced by picosecond time-resolved resonance Raman experiments and ab initio calculation

摘要

The combination of ab initio calculation using the CIS method and experimental vibrational data from picosecond time-resolved Raman measurements leads to a confident picture of the structure of the lowest excited singlet state S-1 (n pi*) of 2,2'-bipyridine. The calculated structure is asymmetric with two dissimilar pyridyl moieties. It can be understood as resulting from a confinement of the excitation in one of the pyridyl rings, breaking the initial ground-state symmetry. The reliability of this structure is attested by good agreement between the derived theoretical vibrational data and the experimental Raman spectra. (c) 2005 Wiley Periodicals, Inc.