Electron Donor–Acceptor (EDA) Complex Formation via Spatial Control of Donor–Acceptor Interactions

Electron donor–acceptor (EDA) complexes are of fundamental importance and practical utility in photoactive molecules, including fluorescence probes and photoredox catalysts. However, the design guidelines for developing efficient intramolecular EDA complexes are still underdeveloped. In this study, we systematically investigate the linker structures between an indole electron donor and a dinitrobenzene electron acceptor within single-molecule EDA complexes to optimize their relative positions and efficiency of the EDA complex formation. We identify trans -1,2-cyclohexanediamine as an optimal linker with a fixed conformation, due to the presence of an intramolecular hydrogen bond. The linker produces a highly efficient EDA complex in both the solution and solid states. This study postulates a versatile core structure for the synthesis of various single-molecule EDA complexes.