Photoisomerization of Spiropyran in Solution: A Surface Hopping Investigation.

We performed a computational investigation of the photoisomerization of an unsubstituted spiropyran in solution using surface hopping molecular dynamics simulations in a semiempirical framework. To bring out the solvent effects on the excited state dynamics, we have run simulations in three different environments: chloroform, methanol, and ethylene glycol. We show that the interaction with a moderately polar solvent such as chloroform has little effect on the dynamics when compared to vacuum results previously obtained by our group. At variance, the interaction with the protic solvents considered considerably affects the reaction mechanism, the quantum yield, and the excited state lifetimes.