Excited state hydrogen transfer dynamics in substituted phenols and their complexes with ammonia: ππ-πσ energy gap propensity and ortho-substitution effect.

Autor:	Pino, G. A., Oldani, A. N., Marceca, E., Fujii, M., Ishiuchi, S.-I., Miyazaki, M., Broquier, M., Dedonder, C., Jouvet, C.
Předmět:	EXCITED state chemistry HYDROGEN SUBSTITUTION reactions PHENOLS COMPLEX compounds AMMONIA BAND gaps
Zdroj:	Journal of Chemical Physics; 9/28/2010, Vol. 133 Issue 12, p124313, 12p
Abstrakt:	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 σ¹ levels in complexes using picosecond pump-probe spectroscopy. Excitation energies to the S1 (ππ^) and S2 (πσ^) states are obtained by quantum chemical calculations 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 ππ^* and πσ^* 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 in terms of the vibronic coupling between the ππ^* and πσ^* states occurring through the out-of-plane distortion of the C-F bond. [ABSTRACT FROM AUTHOR]
Databáze:	Complementary Index
Externí odkaz:

Excited state hydrogen transfer dynamics in substituted phenols and their complexes with ammonia: ππ*-πσ* energy gap propensity and ortho-substitution effect.

Excited state hydrogen transfer dynamics in substituted phenols and their complexes with ammonia: ππ-πσ energy gap propensity and ortho-substitution effect.