Quantum study on photophysical and photochemical process of a new photosensitizer: hypomycin B

Ab initio and CIS theories were employed to study a new type of perylenequinonoid photosensitizer (PQP)—hypomycin B (HMB), which has only one pair of adjacent hydroxyl group and carbonyl group in its peri-region. Geometries, Mulliken charge population, energy, and photophysical and photochemical process in excited state were discussed in detail. The results indicate that HMB exhibits quite similar intramolecular proton transfer (IPT) to perylenequinone, which offers an indirect understanding that the IPT process in perylenequinonoid derivatives (PQD) is a single proton transfer process. There exists the crossing of the potential energy surface of the singlet and triplet so that the intersystem crossing (ISC) can occur. The ISC will increase triplet quantum efficiency, which is the basis for photosensitization of PQP.