TY - JOUR
T1 - Photoreactivity of a push - pull merocyanine in static electric fields
T2 - A three-state model of isomerization reactions involving conical intersections
AU - Xu, X. F.
AU - Kahan, A.
AU - Zilberg, S.
AU - Haas, Y.
PY - 2009/9/10
Y1 - 2009/9/10
N2 - The photochemistry of a prototype push-pull merocyanine is discussed using a simple three-state model. As a derivative of butadiene, the model focuses on two isomerization reactions around the two double bonds of the butadiene backbone. As a molecule substituted by an electron donor and electron acceptor at opposite ends, its structure as well as its photochemistry are expected to be strongly affected by the environment. In polar solvents, a zwitterion transition state for each of the isomerization reactions is stabilized, and its energy is on the same order as that of the biradical one; this leads to the symmetry allowed crossing (S0/S1 conical intersection). It is shown that applying an external electric field or varying the solvent polarity changes the relative energies of the different transition states as well as that of the conical intersection, and thus different photochemical products can be obtained. In particular, the very existence of conical intersections is found to depend on these external parameters. This work provides a theoretical foundation for ideas expressed by Squillacote et al. (J. Am. Chem. Soc. 2004, 126, 1940) concerning the electrostatic control of photochemical reactions.
AB - The photochemistry of a prototype push-pull merocyanine is discussed using a simple three-state model. As a derivative of butadiene, the model focuses on two isomerization reactions around the two double bonds of the butadiene backbone. As a molecule substituted by an electron donor and electron acceptor at opposite ends, its structure as well as its photochemistry are expected to be strongly affected by the environment. In polar solvents, a zwitterion transition state for each of the isomerization reactions is stabilized, and its energy is on the same order as that of the biradical one; this leads to the symmetry allowed crossing (S0/S1 conical intersection). It is shown that applying an external electric field or varying the solvent polarity changes the relative energies of the different transition states as well as that of the conical intersection, and thus different photochemical products can be obtained. In particular, the very existence of conical intersections is found to depend on these external parameters. This work provides a theoretical foundation for ideas expressed by Squillacote et al. (J. Am. Chem. Soc. 2004, 126, 1940) concerning the electrostatic control of photochemical reactions.
UR - http://www.scopus.com/inward/record.url?scp=84962449695&partnerID=8YFLogxK
U2 - 10.1021/jp904097k
DO - 10.1021/jp904097k
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AN - SCOPUS:84962449695
SN - 1089-5639
VL - 113
SP - 9779
EP - 9791
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 36
ER -