Photochemistry of 2‘-Hydroxychalcone. One-Way Cis−Trans Photoisomerization Induced by Adiabatic Intramolecular Hydrogen Atom Transfer
作者:Yasuo Norikane、Hiroki Itoh、Tatsuo Arai
DOI:10.1021/jp0133081
日期:2002.3.1
a novel mechanism and the potential energy surface for the oneway photoisomerization of 2HC were proposed. The photoisomerization of 2HC was induced by hydrogen atom transfer in the excited triplet state. Thus, 2HC can be viewed as a molecule in which the mode of isomerization around the carbon-carbon double bond can be controlled by the remote intramolecular hydrogen bonding. Solvent affected the
通过量子产率测量、瞬态吸收光谱和半经验计算研究了 2'-羟基查耳酮 (2HC) 的分子内氢原子转移和新型单向光异构化。2HC 的反式异构体 (trans-2HC) 不会产生顺式异构体,而 cis-2HC 经过单向异构化后会产生反式-2HC。顺式和反式 2HC 的三重态-三重态吸收光谱相似,并归属于通过激发三重态的分子内氢原子转移产生的互变异构体。trans-2HC的正常形式和互变异构形式的三重态能量通过淬灭实验估计分别为229和177.5 kJ mol -1 。地层中反式2HC和顺式2HC的形成热、前沿分子轨道系数和优化结构、激发单线态、通过半经验(MOPAC93 PM3 / 4CI)计算计算激发的三重态。这些计算与实验观察非常吻合。基于实验观察和理论考虑,提出了2HC单向光异构化的新机制和势能面。2HC 的光异构化是由激发三重态下的氢原子转移引起的。因此,2HC可以被视为一种分子,其中碳