Electronic Resource
College Park, Md.
:
American Institute of Physics (AIP)
The Journal of Chemical Physics
102 (1995), S. 5733-5742
ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The topology and energetics of the potential energy surfaces associated with the 2A1 and 1B2 valence excited states of s-cis butadiene have been investigated via ab initio quantum chemical computations at a level of theory which includes dynamic correlation effects and extended basis sets. The results support a photochemical ring-closure mechanism involving 1B2 and 2A1 reaction/relaxation pathways that are disrotatory. The reaction path on the 2A1 surface begins at a 1B2/2A1 conical intersection and the ground state photoproducts are produced via radiationless decay at a second 2A1/1A1 conical intersection which has been documented in a previous publication. A local Cs equilibrium structure on 1B2 potential energy surface has been optimized using the complete active space-self-consistent field and configuration interaction singles methods. The 1B2/2A1 conical intersection is located near this Cs equilibrium structure and offers a rationalization of the experimentally observed femtosecond lifetime of this state. The observed preferential disrotatory stereochemistry appears to be simply determined by a difference in the energy barriers located along the 2A1 disrotatory and conrotatory paths. This finding is in contrast with the generally accepted notion that the stereochemistry is determined by a different rate of internal conversion at a "disrotatory'' and "conrotatory'' avoided crossing minima. Indeed, no avoided crossing can be located along the 2A1 paths. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.469304
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