A proper understanding of excited state properties of indole derivatives can lead to rational design of efficient fluorescent probes. The optically active and excited states of a series of substituted indoles, where a substituent was placed on position four, were calculated using equation of motion coupled cluster and time dependent density functional theory. The results indicate that most substituted indoles have a brighter second excited state corresponding to experimental absorption maxima, but a few with electron withdrawing substituents absorb more on the first excited state. Absorption on the first excited state may increase their fluorescence quantum yield, making them better probes. Electronic structure methods were found to predict the energies of the systems with electron withdrawing substituents more accurately than those with electron donating substituents. The excited states of both states correlated well with electrophilicity, similar to the experimental trends for the absorption maxima. Overall, these computational studies indicate that theory can be used to predict excited state properties of substituted indoles, when the substituent is an electron withdrawing group.

中文翻译：

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模拟取代基对吲哚衍生物电子激发态的影响


对吲哚衍生物的激发态特性的正确理解可以导致高效荧光探针的合理设计。使用耦合簇的运动方程和时间相关密度泛函理论计算了一系列取代吲哚的旋光态和激发态，其中取代基位于第四位。结果表明，大多数取代吲哚具有与实验吸收最大值相对应的更亮的第二激发态，但少数具有吸电子取代基的吲哚在第一激发态上吸收更多。第一激发态的吸收可能会增加它们的荧光量子产率，使它们成为更好的探针。人们发现，电子结构方法可以比具有供电子取代基的系统更准确地预测具有吸电子取代基的系统的能量。两种状态的激发态与亲电性密切相关，类似于吸收最大值的实验趋势。总体而言，这些计算研究表明，当取代基是吸电子基团时，理论可用于预测取代吲哚的激发态性质。