Ilkhani Ali Reza
Department of Chemistry, Yazd Branch, Islamic Azad University, Yazd, Iran.
Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
J Mol Model. 2019 Jan 2;25(1):8. doi: 10.1007/s00894-018-3900-8.
The pseudo Jahn-Teller effect (PJTE) is employed in CAH (A = O, S, Se, Te), and CEH (E = N, P, As, Sb) with planar configurations to show symmetry breaking phenomena (SBP) in heteronine analogues, and to explain why molecules with (C) high-symmetry configurations cannot maintain planarity and pucker to their (C) and (C) lower-symmetry structures, respectively. To investigate this phenomenon, geometry optimization and frequency calculations through the density functional B3LYP method using the cc-pVTZ basis set (for Te, and Sb cc-pVTZ-PP) were carried out for all compounds in the series. The state average-complete active space self-consistent field wave-function method was employed to calculate the electronic ground and several low-lying excited states to specify the adiabatic potential energy surface along the a and b puckering nuclear displacements. The PJTE (A + A + A') a2 and (A + B + A') b problems were formulated as the effects originating via the PJTE theorem. Moreover, replacing hydrogen atoms in CNH, a stable planar structure, with fluorine ligands demonstrated that SBP occur from C to C symmetry. Furthermore, thermochemical calculations via B3LY/cc-pVTZ illustrated that the planarity of the CE ring is restored in CEH (E = P, As, Sb) anions ,with the change in free energy corresponding to spontaneous deprotonation reactions as 23.67 kJ mol, 21.88 kJ mol, and 16.57 kJ mol, respectively. In fact, despite CEH having a donor electron-pair and potentially being Lewis base compounds, it acts as a Bronsted-Lowry acid releasing a H proton instead in this case.
赝 Jahn-Teller 效应（PJTE）应用于具有平面构型的 CAH（A = O、S、Se、Te）和 CEH（E = N、P、As、Sb）中，以展示杂九元类似物中的对称性破缺现象（SBP），并解释具有（C）高对称构型的分子为何分别不能保持平面性并向其（C）和（C）低对称结构发生褶皱。为研究该现象，使用 cc-pVTZ 基组（对于 Te 和 Sb 为 cc-pVTZ-PP）通过密度泛函 B3LYP 方法对该系列中的所有化合物进行了几何优化和频率计算。采用态平均完全活性空间自洽场波函数方法计算电子基态和几个低激发态，以确定沿 a 和 b 褶皱核位移的绝热势能面。PJTE（A + A + A'）a2 和（A + B + A'）b 问题被表述为由 PJTE 定理产生的效应。此外，用氟配体取代稳定平面结构 CNH 中的氢原子表明，SBP 从 C 对称发生到 C 对称。此外，通过 B3LY/cc-pVTZ 进行的热化学计算表明，在 CEH（E = P、As、Sb）阴离子中 CE 环的平面性得以恢复，自由能变化对应于自发去质子化反应，分别为 23.67 kJ mol、21.88 kJ mol 和 16.57 kJ mol。实际上，尽管 CEH 具有供体电子对且可能是路易斯碱化合物，但在这种情况下它却作为布朗斯特-劳里酸释放出一个 H 质子。
