Constrained Excited-State Structure in Molecular Crystals by Means of the QM/MM Approach: Toward the Prediction of Photocrystallographic Results

The QM/MM method is applied to predict the excited triplet structure of a molecule embedded in a crystal. In agreement with experimental observation, it is found that conformation changes on excitation are severely restricted compared with geometry changes predicted for the isolated molecule. The results are of importance for understanding the photophysical properties of molecular solids.