The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4‐D−C₆H₄−B(Ar)₂ (D=^tBu or NPh₂; Ar=mesityl (Mes) or 2,4,6‐tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state‐of‐the‐art DFT and TD‐DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4‐^tBu−C₆H₄−B(Fmes)₂ 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert‐butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.

中文翻译：

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深入研究具有强电子接受性双（氟甲磺酰基）硼基的三芳基硼烷的光学性质：理论与实验相符

一系列形式为4- DC ₆ C ₄ H ₄ -B（Ar）₂（D = ^t Bu或NPh ₂ ; Ar =甲磺酰基（Mes）或2）的三芳基硼烷的光物理性质（吸收，荧光和磷光）理论上，使用最新的DFT和TD-DFT方法分析了4,6-三（三氟甲基苯基（Fmes）），模拟的发射光谱和计算的衰减速率常数与实验数据非常吻合。包括振动贡献解释了4 ^t Bu-C ₆ H ₄ -B（Fmes）₂ 2的异常光学行为，它在几乎相同的能量下（在冷冻玻璃中为77 K时）显示荧光和磷光。负责磷光振动精细结构的主要正常模式的分析表明，笨重叔丁基组系在苯环被强烈参与。有趣的是，在THF溶剂中，仅对于化合物2，单线态和三线态激发态的计算能量非常相似，这可以解释为什么2与系列中的其他成员相比显示出磷光。