Bridged Photochromic Diarylethenes Investigated by Ultrafast Absorption Spectroscopy: Evidence for Two Distinct Photocyclization Pathways
作者:Stéphane Aloïse、Michel Sliwa、Zuzanna Pawlowska、Julien Réhault、Julien Dubois、Olivier Poizat、Guy Buntinx、Aurélie Perrier、François Maurel、Shouhei Yamaguchi、Michinori Takeshita
DOI:10.1021/ja910813x
日期:2010.6.2
intersection near hot S(1) state is discussed. This second photoclosure reaction is less efficient and both the photocylization yield and overall kinetics depend on solvent polarity (phi = 0.49, tau = 2.5 ps in nonpolar solvent; phi = 0.7, tau = 1.5 ps in polar solvent). In the case of [2.4], for which the distance between the two reactive carbons is larger, a unique photoclosure mechanism is found and a structural
通过稳态和飞秒瞬态光谱研究了两种光致变色二芳基乙烯在理想的光环化构象中被烷基桥阻断,以描述光环化过程:双稳态 1,2-二氰基[2.n]metacyclophan-1-ene,n = 2 ,缩写为[2.2],其非双稳态类似物n = 4,缩写为[2.4]。根据 AM1-CIS 计算和基于结论性 TD-DFT 计算的状态相关图来解释数据。对于 [2.2],在 S(1) 和 S(2) 单线态之间清楚地证明了控制光环化产率的溶剂敏感激发波长阈值。高于和超出该阈值的激发会诱导两种不同的光化学途径。S(1) 垂直激励诱导直接有效(phi 大约 = 0.9-1),和超快(约 120 fs)光环化从 S(1) 开放形式导致基态过渡结构,可能通过锥形交叉,然后到热环化基态,通过振动冷却松弛。在更高的激发能量下,系统经历内部转换到热 S(1) 状态,然后演变为环化 S(1) 状态并通过超快 S(1)-S(0) 内部转换放松。或者,讨论了在热