Abstract In this work, density functional theory and time-dependent density functional theory were performed to investigate intermolecular hydrogen bond (H-bond) effect on Coumarin-1 (C1). The optimized geometric structures of C1 in acetonitrile and methanol (MeOH) revealed that C1 exhibits planar configuration in ground state and locally excited (LE) state. Due to intermolecular H-bond interaction between C1 and MeOH, twisted intramolecular charge transfer (TICT) state with twist configuration exists in excited state for C1–MeOH. The apparent variation of characteristic group frequencies and intensities for IR spectra is ascribed to dramatic charge density changes. Compared with molecular orbitals of LE state, the low charge coupling degree of C1–MeOH in TICT state is induced by twist configuration in TICT state. Indeed, such low charge coupling degree induced TICT state is nonluminous that responsible for low fluorescence quantum yield of C1–MeOH. We not only provide a comprehensive understanding of TICT state deactivation process but also benefits to design new environment-sensitive probe.

中文翻译：

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分子间氢键诱导香豆素1荧光猝灭现象的理论研究

摘要 在这项工作中，密度泛函理论和瞬态密度泛函理论研究了分子间氢键（H-键）对香豆素-1（C1）的影响。C1 在乙腈和甲醇 (MeOH) 中的优化几何结构表明，C1 在基态和局部激发 (LE) 状态下均呈现平面构型。由于 C1 和 MeOH 之间的分子间氢键相互作用，C1-MeOH 的激发态存在具有扭曲构型的扭曲分子内电荷转移 (TICT) 状态。红外光谱特征基团频率和强度的明显变化归因于电荷密度的剧烈变化。与LE态的分子轨道相比，TICT态的C1-MeOH的低电荷耦合度是由TICT态的扭曲构型引起的。确实，这种低电荷耦合度诱导的 TICT 状态是不发光的，导致 C1-MeOH 的荧光量子产率低。我们不仅提供了对 TICT 状态失活过程的全面了解，而且有利于设计新的环境敏感探针。