Štellerová Dagmar, Lukeš Vladimír, Breza Martin
Institute of Physical Chemistry and Chemical Physics STU, Radlinskeho 9, SK-81237 Bratislava, Slovakia.
Molecules. 2024 Nov 28;29(23):5624. doi: 10.3390/molecules29235624.
The distortions and instability of high-symmetry configurations of polyatomic systems in nondegenerate states are usually ascribed to the pseudo-Jahn-Teller effect (PJTE). The geometries of hypericin, isohypericin, and fringelite D were optimized within various symmetry groups. Group-theoretical treatment and (TD-)DFT calculations were used to identify the corresponding electronic states during the symmetry descent. The symmetry descent paths (up to the stable structures without imaginary vibrations) were determined using the corresponding imaginary vibrations as their kernel subgroups starting from the highest possible symmetry group. The vibronic interaction between the ground and excited electronic states relates to an increasing energy difference of both states during the symmetry decrease. This criterion was used to identify possible PJTE. We have shown that the PJTE in these naturally occurring compounds could explain only the symmetry descent paths C → C and C → C in hypericin, and the D → C, D → C → C, and D → C ones in fringelite D. The electric dipole moments of hypericin and its analogs were determined prevailingly by the mutual orientations of the hydroxyl groups. The same held for the energies of frontier orbitals in these systems, but their changes during the symmetry descent were less significant.
多原子体系在非简并态下高对称构型的畸变和不稳定性通常归因于赝 Jahn - Teller 效应（PJTE）。金丝桃素、异金丝桃素和条纹岩 D 的几何结构在不同对称群内进行了优化。采用群论处理和（TD -）DFT 计算来确定对称降低过程中相应的电子态。从最高可能的对称群开始，以相应的虚振动作为其核子群来确定对称降低路径（直至无虚振动的稳定结构）。基态和激发态电子态之间的振动 - 电子相互作用与对称降低过程中两种态的能量差增加有关。该标准用于识别可能的 PJTE。我们已经表明，这些天然存在的化合物中的 PJTE 仅能解释金丝桃素中 C → C 和 C → C 的对称降低路径，以及条纹岩 D 中 D → C、D → C → C 和 D → C 的对称降低路径。金丝桃素及其类似物的电偶极矩主要由羟基的相互取向决定。这些体系中前沿轨道的能量也是如此，但其在对称降低过程中的变化不太显著。
