The synthesis, photophysical characterization, and quantum chemical calculations of a series of benzotriazinyl radicals and their styryl radical trapping products are presented. The benzotriazinyl radicals are non-luminescent but surprisingly the corresponding styryl radical trapping products exhibit high fluorescence quantum yields (up to 60% in some cases), making them highly valuable probes or labels. Additionally, the influence of the substitution pattern on the optical properties of the radical trapping products was observed experimentally and interpreted by means of quantum chemical calculations. Specific substitution patterns showed a bathochromic shift compared to the unsubstituted compound. Computationally, it was shown that this substitution pattern leads to a stronger energetic stabilization of the lowest unoccupied molecular orbital than the highest occupied molecular orbital. Analysis of the influence of the substitution pattern on the optical properties showed a bathochromic shift in several examples, which was interpreted by means of quantum chemical calculations.

中文翻译：

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前荧光苯并三嗪基自由基的电子效应：组合的实验和理论研究

介绍了一系列苯并三嗪基自由基及其苯乙烯基自由基捕获产物的合成，光物理性质和量子化学计算。苯并三嗪基自由基是不发光的，但令人惊讶的是，相应的苯乙烯基自由基捕获产物显示出高的荧光量子产率（在某些情况下高达60％），使其成为非常有价值的探针或标记。另外，通过实验观察了取代图案对自由基捕获产物的光学性质的影响，并通过量子化学计算来解释。与未取代的化合物相比，特定的取代模式显示出红移。计算上 结果表明，这种取代模式导致最低未占据分子轨道的能量稳定高于最高占据分子轨道。分析取代图案对光学性质的影响在几个实例中显示出红移，这是通过量子化学计算来解释的。