Nonadiabatic dynamics simulation of photoisomerization mechanism of photoswitch azodicarboxamide: Hydrogen bonding effects

Photoswitches triggered by light are of vital importance for the development of photoactive functional materials. Here, we study the photodynamics of the new photoswitch azodicarboxamide by using the on-the-fly surface hopping method. Its nonadiabatic relaxation is determined to be a cooperative process by simultaneous N=N torsion and two N-C bond rotations. The fast N=N twisting contributes to E-Z photoisomerization while slow N=N twisting leads to nonreactive E-E relaxation. In addition, intermolecular hydrogen bonding with water promotes the N=N torsion, leading to a higher E-Z quantum yield. The hydrogen bonding is also found to enhance the non -Kasha E-Z photochemistry