Theoretical study on the ground and excited state intramolecular proton transfer in perylenequinone

The intramolecular proton transfer of perylenequinone (PQ) in the ground state S0 and the excited states S1 and T1 has been studied at the HF/CIS/6-31g level of theory. It is found that the process can be viewed as a proton transfer in S0 and S1, while it is coupled with an electronic transfer through the conjugated system in T1. The barrier of proton transfer in the S1 is 10.38 kJ/mol, which agrees with the experimental result of hypocrellin A and offers good evidence that the experimental observed process of hypocrellin A is also single proton transfer.