Abstract The properties of phosphole-based π-conjugated compounds could be well tuned via simple chemical modification. Four π-conjugated groups with different electronic nature including naphthalen-2-yl, 4-methoxyphenyl, 4-Methyl benzoate, and 4-benzonitrile were introduced to the C8 position of 5-phenylbenzo[b]phosphindole 5-oxide (PhBPO) to reveal the relationship between structures and properties. Density functional theory (DFT) calculations were carried out to comparatively study the ground state geometries, orbital energy gaps, infrared (IR) spectra, UV–vis spectra, and fluorescence (FL) spectra of the five PhBPO derivatives. Good correspondences between the simulated and experimental IR and UV–vis spectral properties were found, proving the feasibility of the DFT method. The IR and Uv-vis spectra were assigned and explained in detail on the basis of the calculation results and the substituional effect of different substituents on the structure and spectral properties was revealed. The large FL oscillator strengths indicate these PhBPO derivatives are good candidates for fluorescent materials. PhBPO derivatives possess easy-to-modify sites and thus can be further utilized as functional materials.

中文翻译：

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5-苯基-5H-苯并[b]膦吲哚5-氧化物及其取代衍生物的结构和光谱性质：基于密度泛函理论计算的取代效应研究

摘要 基于磷的 π 共轭化合物的性质可以通过简单的化学修饰得到很好的调节。将萘-2-基、4-甲氧基苯基、4-苯甲酸甲酯和4-苄腈四个具有不同电子性质的π-共轭基团引入5-苯基苯并[b]膦吲哚5-氧化物（PhBPO）的C8位，揭示结构和性质之间的关系。进行密度泛函理论 (DFT) 计算以比较研究五种 PhBPO 衍生物的基态几何形状、轨道能隙、红外 (IR) 光谱、紫外-可见光谱和荧光 (FL) 光谱。发现模拟和实验 IR 和 UV-vis 光谱特性之间的良好对应，证明了 DFT 方法的可行性。在计算结果的基础上对红外光谱和紫外可见光谱进行了分配和详细解释，揭示了不同取代基对结构和光谱性质的取代作用。大的 FL 振荡器强度表明这些 PhBPO 衍生物是荧光材料的良好候选者。PhBPO 衍生物具有易于修饰的位点，因此可以进一步用作功能材料。