Inter- and Intramolecular Electron-Transfer Reduction Properties of Coronenediimide Derivatives via Photoinduced Processes

Coronenediimide derivatives with five- or six-membered maleimide groups [denoted as Cor(5Im)2 and Cor(6Im)2] were employed as electron acceptors to examine the electron-transfer reduction properties through photochemical and electrochemical measurements. In steady-state absorption and fluorescence measurements, the spectra of Cor(5Im)2 and Cor(6Im)2 became remarkably broadened and red-shifted as compared to pristine coronene (Cor). These results are supported by electrochemical measurements and DFT calculations. The rate constants of photoinduced intermolecular electron transfer from various donor molecules to 3Cor(5Im)2* or 3Cor(6Im)2* are determined by nanosecond transient absorption measurements. Although the back-electron-transfer reactions examined in this study proceed with the diffusion-limited rate constant in benzonitrile (PhCN), the rate constants of forward electron-transfer reactions (ket) increase with an increase in the driving force of electron transfer (−ΔGet) to approach the diffusion-limited rate constant. When the driving force dependence of ket was fit on the basis of the Marcus theory of electron transfer, the reorganization energy (λ) of the electron-transfer reduction of Cor(5Im)2 and Cor(6Im)2 are determined to be 0.77 and 1.15 eV, respectively. A new covalently perylene-linked donor–acceptor dyad was also synthesized to investigate the dynamics of ultrafast photoinduced intramolecular electron transfer.