Intermolecular-charge-transfer-induced fluorescence quenching in protic solvent

•We theoretically investigated the fluorescence quenching in protic solvent.•We analyzed the effect of charge transfer on the quenching process.•The main method we used is relaxed scans.•The conical intersection was found in potential energy profiles.•The saddle point was found in potential energy surface.

The fluorescence quenching of fluorenone in protic solvent has been extensively investigated, and the intermolecular hydrogen bond was found to play a crucial role. Unfortunately, the mechanism at atomic level is still not clear. In the present work, we theoretically put forward the charge transfer along the hydrogen bond in the excited states. The vertical excitation energies of the fluorenone-methanol complex as well as the potential energy profiles and surfaces of the vertical excited states and charge transfer states were calculated by using the ab initio electronic-structure methods. The photochemical reactions occurring in the diverse charge transfer states were compared and their decisiveness to the fluorescence quenching was discussed in the paper.

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