The new ratiometric fluorescent probe 2-(4-(dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4h-chromen-4-one (HOF) monitoring of methanol in biodiesel was discovered experimentally (T. Y. Qin et al., Sens. Actuators, B, 2018, 277, 484–491). But the experimental study did not report the reaction mechanism in detail. In this study, density functional theory (DFT) and time-density functional theory (TDDFT) methods were used to theoretically study the excited-state intramolecular proton transfer (ESIPT) process of the HOF molecule. The molecular structure in the ground state and the excited state was optimized, and the infrared vibrational spectra, the frontier molecular orbitals, the charge transfer, the potential energy curves and the transition-state structures were calculated. The calculated results prove that the solvent polarity has a great influence on the ESIPT reaction of the HOF molecule. As the solvent polarity increased, the intensity of the intramolecular hydrogen bond decreased, and ESIPT was more difficult to occur. This work has studied the mechanism of the ESIPT reaction in more detail, and paved the way for future research on HOF molecules.

中文翻译：

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溶剂环境对2-（4-（二甲基氨基）苯基）-3-羟基-6,7-二甲氧基-4 h -chromen-4-one †中激发态分子内质子转移的影响†

通过实验发现了新型比例荧光探针2-（4-（二甲基氨基）苯基）-3-羟基-6,7-二甲氧基-4 h-铬n-4-酮（HOF）监测生物柴油中的甲醇（TY Qin等。，致动器，B，2018，277，484–491）。但是实验研究并未详细报道其反应机理。在这项研究中，使用密度泛函理论（DFT）和时间密度泛函理论（TDDFT）方法来理论上研究HOF分子的激发态分子内质子转移（ESIPT）过程。优化了基态和激发态的分子结构，计算了红外振动光谱，前沿分子轨道，电荷转移，势能曲线和过渡态结构。计算结果证明，溶剂极性对HOF分子的ESIPT反应有很大影响。随着溶剂极性的增加，分子内氢键的强度降低，并且更难以发生ESIPT。