Quantum-chemical calculations of phenyl-substituted pyridinium cations established the formation of two non-rigid equilibrium structures in a singlet excited S₁ state. These two structures are characterized by a significant torsion of the methyl group and flattened geometry of the phenyl rings relative to the plane of the heteroaromatic ring, as well as sp³ hybridization of a nitrogen atom. Structural features of the S₁ equilibrium structures and their deviation from the pyridinium cation geometry in the ground state explain the experimentally detected abnormally large Stokes shift.

中文翻译：

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激发态结构非刚性吡啶阳离子的几何结构。

_{苯基取代的吡啶阳离子的量子化学计算确定了在单线态激发 S 1}状态下两个非刚性平衡结构的形成。这两种结构的特征在于甲基的显着扭转和苯环相对于杂芳环平面的扁平几何形状，以及氮原子的sp ^3杂化。S ₁平衡结构的结构特征及其与基态吡啶阳离子几何结构的偏差解释了实验检测到的异常大的斯托克斯位移。