BN 吲哚的紫外光电子能谱：实验和计算电子结构分析,Journal of the American Chemical Society

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BN 吲哚的紫外光电子能谱：实验和计算电子结构分析
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2014-08-11 , DOI: 10.1021/ja5063899
Anna Chrostowska ₁ , Senmiao Xu , Audrey Mazière , Katherine Boknevitz , Bo Li , Eric R Abbey , Alain Dargelos , Alain Graciaa , Shih-Yuan Liu

Affiliation

我们使用组合的紫外光电子能谱 (UV-PES)/计算化学方法对吲哚的两种 BN 等排体进行了全面的电子结构分析。记录了外部 BN 吲哚 I 和熔融 BN 吲哚 II 的气相 He I 光电子谱，通过密度泛函理论计算进行评估，并与天然吲哚进行比较。这些吲哚的第一电离能是天然吲哚 (7.9 eV)、外部 BN 吲哚 I (7.9 eV) 和融合 BN 吲哚 II (8.05 eV)。计算确定的分子偶极矩的顺序是：天然吲哚 (2.177 D) > 融合 BN indole II (1.512 D) > 外部 BN indole I (0.543 D)。UV-vis 吸收光谱中的 λmax 顺序为：熔融 BN 吲哚 II (292 nm) > 外部 BN indole I (282 nm) > 天然吲哚 (270 nm)。观察到的研究吲哚与二甲基亚胺氯化物作为亲电试剂的相对亲电芳香取代反应性如下：稠合 BN 吲哚 II > 天然吲哚 > 外部 BN 吲哚 I，这种趋势与 3 位的 π 轨道系数相关。与核无关的化学位移计算表明，将硼引入芳香族 6π 电子系统会导致芳香性降低，这可能是由于更强的键定位。苯和甲苯等简单单环芳烃系统的 BN 等排体的趋势和结论不一定转化为双环吲哚核心。因此，需要从系统到系统单独评估由 BN/CC 等排性引起的电子结构后果。

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UV-Photoelectron Spectroscopy of BN Indoles: Experimental and Computational Electronic Structure Analysis

We present a comprehensive electronic structure analysis of two BN isosteres of indole using a combined UV-photoelectron spectroscopy (UV-PES)/computational chemistry approach. Gas-phase He I photoelectron spectra of external BN indole I and fused BN indole II have been recorded, assessed by density functional theory calculations, and compared with natural indole. The first ionization energies of these indoles are natural indole (7.9 eV), external BN indole I (7.9 eV), and fused BN indole II (8.05 eV). The computationally determined molecular dipole moments are in the order: natural indole (2.177 D) > fused BN indole II (1.512 D) > external BN indole I (0.543 D). The λmax in the UV–vis absorption spectra are in the order: fused BN indole II (292 nm) > external BN indole I (282 nm) > natural indole (270 nm). The observed relative electrophilic aromatic substitution reactivity of the investigated indoles with dimethyliminium chloride as the electrophile is as follows: fused BN indole II > natural indole > external BN indole I, and this trend correlates with the π-orbital coefficient at the 3-position. Nucleus-independent chemical shifts calculations show that the introduction of boron into an aromatic 6π-electron system leads to a reduction in aromaticity, presumably due to a stronger bond localization. Trends and conclusions from BN isosteres of simple monocyclic aromatic systems such as benzene and toluene are not necessarily translated to the bicyclic indole core. Thus, electronic structure consequences resulting from BN/CC isosterism will need to be evaluated individually from system to system.

更新日期：2014-08-11

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