Oxygen migration and optical properties of coronene oxides and their persulfurated derivatives: insight into the electric field effect and the oxygen-site dependence†
Oxygen migration and spectroscopic properties of coronene (C24) epoxides and persulfurated coronene (PSC) oxides have been investigated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The rim-oxide is predicted to be more energetically favorable than the oxygen-centered configuration, and the application of an external electric field can accelerate the epoxy migration from the middle to the edge of the molecule. The predicted electronic absorptions and emissions of the C24 epoxides strongly depend on the location of oxygen. In particular, the stable edge-epoxide C24d3 has the largest radiative decay rate (kr) and the smallest non-radiative decay rate (knr), suggesting relatively strong fluorescence emission. On the contrary, absorptions and emissions of the PSC oxides are less changed, compared to those of the pristine PSC. On-the-fly trajectory surface hopping dynamics simulations reveal that the nonadiabatic S1 → S0 decay of the C24 epoxides is triggered by C–O bond stretching, and thus the radiative and nonradiative features depend on the C–O bond strength. The present results indicate that the oxygen diffusion on the basal plane of graphene oxides is easily tuned by the external electric field and their optoelectronic properties show a notable oxygen-site dependence.