Theoretical study on the photophysical and photochemical characteristics of aluminum ion-complexed perylenequinone

The photophysical and photochemical characteristics of the aluminum ion-complexed perylenequinone (Al3+-PQ) at different chain length have been explored employing the quantum chemical method in this paper. It is revealed firstly, the optimized structures of the complexes at different chain lengths are all one-dimension polymeric chains in the ground state. Secondly, the chelation reaction not only decreases the molecular EHOMO, ELUMO and ΔE, but also shifts the excitation spectra bathochromatically. In addition, based on the present calculation results, the first triplet excitation energy of the complexes at different chain length can directly be transferred to molecular oxygen to generate the singlet excited molecular oxygen (1O2) (Type II). On the contrary, the semiquinone anion radicals (Al3+-PQ−) cannot react with triplet molecular oxygen to form the superoxide anion radical (O2−), which indicates photosensitization mechanism Type I is not involved in the photodynamic action of Al3+-PQ.