线性响应和两种态特定方法模拟AF350电子跃迁的溶剂效应

在极化连续模型框架下比较了线性响应与两种不同态特定方法计算的溶液中Alexa Fluor 350(AF350)分子激发能和光谱移动值的差异. AF350的第一激发态S0→S1电子跃迁属于π→π^*跃迁, 主要对应于最高占据分子轨道(HOMO)到最低空轨道(LUMO)的跃迁. 该分子激发态偶极矩大于基态偶极矩, 激发态时溶质溶剂相互作用比基态时更强, 随着溶剂极性增大, 会发生光谱红移的现象. 与实验值相比, 线性响应和两种态特定方法均高估了激发能, 其中以IBSF(Improta-Barone-Scalmani-Frisch)方法得到的激发能最小, 矫正的基态反应场方法(cGSRF)得到的激发能最大. 对于光谱移动值, 3种方法与实验值相比都偏小, 线性响应方法(LR)计算出的误差最大, 而IBSF方法得到的结果与实验值最吻合, 是预测溶液中AF350分子激发能和光谱移动值最准确的方法. 对比了Marcus传统理论和基于约束平衡的非平衡溶剂化理论的结果, 发现后者得到的激发能和光谱移动值更接近于实验值.

Solvent Effect for Electron Transition of Alexa Fluor 350 with Linear Response and State-specific Methods

The linear response and two state-specific methods for calculating the difference in the excitation energy and spectral shift of Alexa Fluor 350（AF350） in solution were compared within the framework of pola-rizable continuum model（PCM）. Compared with the experimental values， it is found that both the linear response and the two state-specific methods overestimate the excitation energy. Among them， the excitation energy obtained by IBSF method is the smallest and that by cGSRF method is the largest. As for the spectral shift value， the three methods are relatively small compared with the experimental value， and the LR method has the lar-gest calculated error， while the IBSF method is the most accurate method to predict the excitation energy and spectral shift of AF350. In addition， Marcus’s traditional theory was compared with the new non-equilibrium solvation theory based on constrained equilibrium， and it was found that the latter’s results are more consistent with the experimental values.