Double-proton transfer mechanism in 1,8-dihydroxydibenzo[a,c]phenazine: a TDDFT and ab initio study

Abstract

The double-proton transfer mechanism in the newly synthesized molecule 1,8-dihydroxydibenzo[a,c]phenazine containing two hydrogen bonds is investigated by means of the time-dependent density functional theory and resolution-of-identity second-order approximate coupled-cluster methods. Both reaction paths of the concerted and the stepwise mechanisms are examined, and the results show that the double-proton transfer is likely to occur in the excited state following the stepwise mechanism in the gas phase at the lowest excitation energy. Based on the calculated potential energy scheme, the single-proton transfer and the double-proton transfer are likely to coexist, with the former is expected to occupy in a significant number. The concerted reaction path of C 2 symmetry is found to be less preferred compared with the stepwise reaction path, and also could be dynamically open due to the small activation energy.