Carbanion Photochemistry. 8 Effect of Substituent Reduction Potential on the Ground- and Excited-State Isomerization of 2-Aryl-1,3-diphenylpropenyl Anions.

Article abstract of DOI:10.1021/jo00218a009

The ground- and excited-state chemistry of 2-aryl-1,3-diphenylpropenyl anions is readily described by a Hueckel model.Because of the antisymmetric nonbonding molecular orbital, in the ground state none of the charge is distributed in the central ring.In the excited state, a nonbonding electron is promoted to a symmetric orbital which is localized on the central aryl ring.Thus lowering the reduction potential of the substituent stabilizes the excited state toward electron-transfer-initiated isomerization of cis-stilbene.Conversely, the more stabilized excited states undergo more efficient E,Z isomerization.Finally, if the central substituent is a 4-chlorophenyl group, photoinduced chloride elimination occurs.