Theoretical study on counter anion- and solvent-dependent fluorescence quenching mechanism of 2-phenylbenzo[b]phospholium salts

Recently reported highly fluorescent 2-phenylbenzo[b]phospholium salt shows an interesting photochemical property. While the counter anion and solvent dependency indicate that the salt is mainly responsible for the absorption and fluorescence spectra, the fluorescence decay clearly depends on the counter anion. In the present study, the detailed mechanism is elucidated using quantum chemical computation and its hybrid with statistical mechanics called 3D-RISM-SCF. Based on the careful exploration of plausible structures of the ion pairs in the methanol and dichloromethane solution, we identify the structure of the charge transfer state, the key on the photoprocess.

Automated summary

The highly fluorescent 2-phenylbenzo[b]phospholium salt recently reported exhibits interesting photochemical properties. While the absorption and fluorescence spectra are mainly influenced by the counter anion and solvent, the fluorescence decay is clearly affected by the counter anion. Through quantum chemical computation and the hybrid method 3D-RISM-SCF, the detailed mechanism of the photoprocess is elucidated by exploring plausible structures of ion pairs in methanol and dichloromethane solutions and identifying the charge transfer state.