Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
J Phys Chem A. 2010 Aug 5;114(30):7886-91. doi: 10.1021/jp1036102.
A series of quinoline/isoquinoline-pyrazole isomers (I-III), in which the pyrazole moiety is in a different substitution position, was strategically designed and synthesized, showing a system with five-membered intramolecular hydrogen bonding. Despite the similarity in molecular structure, however, only I undergoes excited-state intramolecular proton transfer, as evidenced by the distinct 560 nm proton-transfer emission and its associated relaxation dynamics. The experimental results support a recent theoretical approach regarding the conjugation effect on a proton (or hydrogen atom) transfer reaction (J. Phys. Chem. A 2009, 113, 4862-4867). The concept simply predicts that more extended pi conjugation, i.e., resonance, for proton-transfer tautomer species could allow for efficient delocalization of excess charge in the reaction center, resulting in a larger thermodynamic driving force for proton transfer.
一系列喹啉/异喹啉-吡唑异构体（I-III）被策略性地设计和合成，其中吡唑部分处于不同的取代位置，形成了一个具有五元分子内氢键的体系。尽管分子结构相似，但只有 I 经历了激发态分子内质子转移，这可以从明显的 560nm 质子转移发射及其相关的弛豫动力学中得到证明。实验结果支持了最近关于质子（或氢原子）转移反应共轭效应的理论方法（J. Phys. Chem. A 2009, 113, 4862-4867）。这个概念简单地预测，对于质子转移互变异构体物种，更大的π共轭，即共振，可以允许在反应中心有效离域过剩电荷，从而导致质子转移的更大热力学驱动力。
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