Excited state hydrogen transfer dynamics in substituted phenols and their complex with ammonia: Energy gap propensity and ortho-substitution effect

G. A. PINO; A. N. OLDANI; E. MARCECA; M. FUJII; S-I. ISCHIUCHI; M. MIYAZAKI; M. BROQUIER; C. DEDONDER-LARDEUX; C. JOUVET

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Año: 2010 vol. 133 p. 124313 - 124313

0021-9606

Lifetimes of the first electronic excited state (S1) of fluorine and methyl (o-, m- and p-) substituted phenols and their complexes with one ammonia molecule have been measured for the 00 transition and for the intermolecular stretching s1 levels in complexes, using picosecond pump-probe spectroscopy. Excitation energies to the S1 pp* and S2 ps* states are obtained by the quantum chemical calculation at the MP2 and CC2 level using the aug-cc-pVDZ basis set for the ground state and the S1 optimized geometries. The observed lifetimes and the energy gaps between the pp* and ps* states show a good correlation, the lifetime being shorter for a smaller energy gap. This propensity suggests that the major dynamics in the excited state concerns an excited state hydrogen detachment or transfer (ESHD/T) promoted directly by a S1/S2 conical intersection, rather than via internal conversion to the ground state. A specific shortening of lifetime is found in the o-fluorophenol-ammonia complex and explained by considering the out-of-plane distortion of the C-F bond caused by a pseudo Jahn-Teller effect.