Reaction Mechanism of Photodeamination Induced by Excited-State Intramolecular Proton Transfer of the Anthrol Molecule

摘要

The photodeamination reaction of the anthrol molecule generating the high-activity quinone methide intermediate has been investigated (J. Org. Chem. 2017, 82, 6006-6021), though lacking careful explanation for its reaction mechanism. In our research, the mechanism of the anthrol molecule photodeamination induced by excited-state intramolecular proton transfer was reported for the first time. Absorption and emission spectra calculated for the work presented here agreed well with experimental results. To propose a molecular-level explanation of the photodeamination reaction, we calculated bond parameters, corresponding infrared vibrational frequencies, Mayer bond orders, and visualized frontier molecular orbitals of different molecules, and the hydrogen bond strengthening behavior in excited states was confirmed, enhancing the excited state intramolecular proton transfer of the anthrol molecule. Moreover, we concluded that photoisomerization weakened the bond strength between nitrogen and carbon atoms, which promoted the photodeamination reaction. Finally, for visually and quantificationally revealing the photodeamination mechanism, we have established the three-dimensional potential energy surfaces for the deamination reaction in different electronic states and calculated the corresponding reaction Gibbs free energies, it can be confirmed that the photodeamination reaction of the anthrol molecule must be induced by a proton transfer reaction in the excited state.