Coumarin-chalcone hybrids have attracted much attention in recent years due to their important optical properties. Herein, the photophysical properties of a series of coumarinyl chalcones and the sensing mechanism for H₂S of a related fluorescent probe CC-DNP were investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The predicted spectral properties agree well with the experimental results, which allowed an assignment of the spectra. Our calculations successfully clarified the experimental observed fluorescence “off-on” effect and the fluorescent quenching mechanism of the probe. The results revealed that the first excited state (S₁) of the probe CC-DNP is a dark state with obvious charge transfer from coumarin unit to 2,4-dinitrophenyl (DNP) moiety, which results in the fluorescence quenching via the nonradiative photoinduced electron transfer (PET) process. On the other hand, the excited state S₁ in the thiolysis product CC-OH decayed directly to S₀, and thus the fluorescence is recovered.

香豆素-查尔酮杂化物由于其重要的光学性质而近年来引起了很多关注。在本文中，使用密度泛函理论（DFT）和时变密度泛函理论（TDDFT）方法研究了一系列香豆素查耳酮的光物理性质以及相关荧光探针CC-DNP对H ₂ S的感应机理。预测的光谱特性与实验结果非常吻合，可以对光谱进行分配。我们的计算成功地阐明了实验观察到的荧光“关闭”效应和探针的荧光猝灭机理。结果表明，探针CC-DNP的第一激发态（S ₁）是一种暗态，具有从香豆素单元到2,4-二硝基苯基（DNP）部分的明显电荷转移，这会通过非辐射光致电子转移（PET）过程导致荧光猝灭。另一方面，硫解产物CC-OH中的激发态S ₁直接衰减为S ₀，因此恢复了荧光。