Photophysics and photostability of adenine in aqueous solution: A theoretical study

The sequential Monte Carlo/CASPT2 approach was employed to investigate deactivation and emission processes from the lowest-lying ππ∗ and nπ∗ excited states of 9H-adenine in aqueous solution. It is found that conical intersections connecting the ππ∗ and nπ∗ states with the ground state are also present in solution, whereas the barriers for the deactivation paths are significantly smaller on solvated conditions. The large destabilization of the nπ∗ state found in solution possibly prevents its involvement in the deactivation photophysics and explains the change from a bi- to a mono-exponential decay for the molecule in the gas phase and solution, respectively.