科研之友
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摘要
Density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods have been performed to investigate the ground and exited states intermolecular multiple protons transfer process of 3-hydroxy-2-(thiophen-2-yl)chromen-4-one (3-HTC) in methanol solvent. We demonstrated that the intermolecular hydrogen bonds formed between 3-HTC and CH3OH are strengthened at the first single excited state by comparing the bond parameters and infrared vibrational spectra with those in So state, which provides the possibility for exited state intermolecular multiple protons transfer reaction. Based on the potential energy surface/curve at So state and S1 state, a CH3OH-assist exited state simultaneous double proton transfer mechanism has been proposed, whose reaction barrier is slightly lower than the case of intramolecular single proton transfer reaction reported previously (RSC advances, 2016, 6, 96147) and the case of two CH3OH assisted exited state multi-proton transfer reaction; in comparison, the high potential barrier heights among the local minima on the So surface imply that the ground state double proton transfer reaction is significantly inhibited. Moreover, the absorption and fluorescence spectra of 3-HTC in CH3OH solvent were simulated for the first time, which haven't been reported in the previous experimental and theoretical studies. Our calculations predicted the dual fluorescence behavior, which corresponds to Stokes shifted emissions of 3-HTC-CH3OH complex and its double protons transfer phototautomer, respectively.
