The substituted effect on excited-state intramolecular proton transfer (ESIPT) of o-LHBDI derivatives (4R-o-LHBDI) was investigated by DFT and TD-DFT methods. The structures of 4R-o-LHBDI (R: OH, NH₂, CN, NO₂, CF₃) were fully optimized, and the H-bond distances, bond angles, and infrared spectra of the atoms involved in PT process in the S₀ and S₁ states were analyzed. The absorption and fluorescence spectra were calculated, and the potential energy curves in both S₀ and S₁ states were constructed. Moreover, the effects of different substituents on the ESIPT mechanism of 4R-o-LHBDI (R: OH, NH₂, CN, NO₂, CF₃) were studied. The results indicate that ESIPT in the 4R-o-LHBDI is a little harder to proceed than that in o-LHBDI since the ESIPT barrier of 4R-o-LHBDI is slightly bigger than that value of o-LHBDI. When the substituent has stronger electron-withdrawing ability or weaker electron-donating ability, the ESIPT process has the smaller potential barrier.

Graphical abstract

中文翻译：

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o-LHBDI衍生物的激发态分子内质子转移（ESIPT）的光物理性质的替代控制：TD-DFT研究。

通过DFT和TD-DFT方法研究了邻-LHBDI衍生物（4R- o- LHBDI）对激发态分子内质子转移（ESIPT）的取代作用。的结构4R- Ô -LHBDI（R：OH，NH ₂，CN，NO ₂，CF ₃）进行全面优化，和H-键长，键角，以及参与PT过程中的原子的红外光谱分析了S ₀和S ₁状态。计算了吸收光谱和荧光光谱，并绘制了S ₀和S ₁态的势能曲线。此外，不同取代基对4R-的ESIPT机理的影响研究了邻-LHBDI（R：OH，NH ₂，CN，NO ₂，CF ₃）。结果表明，ESIPT在4R- Ô -LHBDI是有点难以进行比ö -LHBDI因为4R-的ESIPT屏障ø -LHBDI大于该值稍大Ò -LHBDI。当取代基具有较强的吸电子能力或较弱的给电子能力时，ESIPT工艺的势垒较小。

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