Hazra Montu K, Chakraborty Tapas
Department of Chemistry, Indian Institute of Technology, Kanpur, UP 208016, India.
J Phys Chem A. 2006 Jul 27;110(29):9130-6. doi: 10.1021/jp060687v.
A 1:1 hydrogen-bonded complex between 2-pyridone and formic acid has been characterized using laser-induced-fluorescence excitation and dispersed fluorescence spectroscopy in a supersonic jet expansion. Under the same expansion condition, the fluorescence signal of the tautomeric form of the complex (2-hydroxypyridine...formic acid) is absent, although both the bare tautomeric molecules exhibit well-resolved laser-induced-fluorescence spectra. Quantum chemistry calculation at the DFT/B3LYP/6-311++G** level predicts that in the ground electronic state the activation barrier for tautomerization from hydroxy to keto form in bare molecules is very large (approximately 34 kcal/mol). However, the process turns out to be nearly barrierless when assisted by formic acid, and double proton transfer occurs via a concerted mechanism.
利用超音速喷射膨胀中的激光诱导荧光激发和色散荧光光谱对2-吡啶酮与甲酸之间1:1的氢键复合物进行了表征。在相同的膨胀条件下，复合物互变异构体形式（2-羟基吡啶……甲酸）的荧光信号不存在，尽管两种裸互变异构体分子都表现出分辨率良好的激光诱导荧光光谱。在DFT/B3LYP/6-311++G**水平上的量子化学计算预测，在基态电子态下，裸分子中从羟基到酮形式的互变异构化活化能垒非常大（约34千卡/摩尔）。然而，在甲酸的辅助下，该过程几乎没有能垒，并且通过协同机制发生双质子转移。
