TDDFT方法研究两个基于Michael反应的氰离子传感器的不同传感机理

利用含时密度泛函方法计算了两个具有类似结构的传感器分子a和b的氰离子传感机理. 结果证实，传感器分子a在基态和S₁态下有着类似的几何构型. 在质子性溶剂水中，氰离子能与传感器分子a发生Michael加成反应，水溶液提供质子，促使最终的α,β-加成产物的生成. 而此加成产物在S₁态下会发生构型变化，导致荧光的猝灭. 传感器分子b的S₁态与基态构型相比发生了构型扭转，并且在非质子性溶剂乙腈中，也可以与氰离子发生Michael加成反应. 由于乙腈

TDDFT Study on Different Sensing Mechanisms of Similar Cyanide Sensors Based on Michael Addition Reaction

The solvents and substituents of two similar fluorescent sensors for cyanide, 7-diethylamino-3-formylcoumarin (sensor a) and 7-diethylamino-3-(2-nitrovinyl)coumarin (sensor b), are proposed to account for their distinct sensing mechanisms and experimental phenomena. The time-dependent density functional theory has been applied to investigate the ground states and the first singlet excited electronic states of the sensor as well as their possible Michael reaction products with cyanide, with a view to monitoring their geometries and photophysical properties. The theoretical study indicates that the protic water solvent could lead to final Michael addition product of sensor a in the ground state, while the aprotic acetonitrile solvent could lead to carbanion as the final product of sensor b. Furthermore, the Michael reaction product of sensor a has been proved to have a torsion structure in its first singlet excited state. Correspondingly, sensor b also has a torsion structure around the nitrovinyl moiety in its first singlet excited state, while not in its carbanion structure. This could explain the observed strong fluorescence for sensor a and the quenching fluorescence for the sensor b upon the addition of the cyanide anions in the relevant sensing mechanisms.