Investigating the photo-relaxation mechanism of 6-azauracil through ab initio nonadiabatic molecular dynamics simulations

On-the-fly ab initio molecular dynamics simulations were performed to study the decay dynamics of photo-excited 6-azauracil. The Zhu–Nakamura trajectory surface hopping method was used to determine the nonadiabatic transitions across different electronic states. The lifetime of the photoexcited S2 state was estimated to be 201 fs, which is in line with the experimentally measured lifetime (Hua et al., 2015). The results of the molecular dynamics simulations revealed that the internal conversion from S2 to S1 is facilitated by the destabilization of the ground state caused by molecular ring puckering. [Display omitted] •The decay dynamics of 6-AU was investigated using ab initio MD simulations.•The lifetime of the S2 state was 201 fs.•The internal conversion is facilitated by out-of-plane vibrational motions.