双光子协同光化学周环反应的选择规则

Rules of Two-Photon Concerted Photochemical Pericyclic Reactions and Its Difference from Woodward-Hoffman Rules for One-Photon Cases

从理论和实验两方面比较了双光子(频率)和相应的单光子(频率2)协同周环反应。二者常得到不同的产物,表明Woodward-Hoffman规则不适用于双光子反应。为解释这一差异,提出用线性多烯烃的HudsonKohler态而不是休克尔分子轨道作为反应中双光子激发产生的最低激发态。根据这一能态的轨道对称性,并利用前线轨道理论,给出了双光子周环反应的选择规则。

A two-photon（ with frequency） reaction（ TPR） is compared with its corresponding one photon（ with frequency 2） counterpart（ SPR） both experimentally and theoretically.TPR often yields different products from its SPR,suggesting Woodward-Hoffman Rules do not apply for TPR.To explain the difference,it is proposed that Hudson-Kohler state of polyenes（ HKSP）,rather than the state in Huckel molecular orbital theory,acts as the lowest-lying excited state for the two-photon absorption（ TPA） involved in TPR.The selection rules for pericyclic TPR are derived based on the symmetry of HKSP and frontier orbital theory.