UV-laser photochemistry: diffusion-controlled trapping of cyclic 1,3-diradicals by molecular oxygen - conformational effects on triplet lifetimes
作者:Waldemar Adam、Peter Hoessel、Walter Huemmer、Herbert Platsch、R. Marshall Wilson
DOI:10.1021/ja00258a074
日期:1987.11
and hence it should have a relatively long triplet lifetime. In contrast, the rigid puckered bicyclo(2.2.1)hepta-2,7-diyl should be the most short-lived species of the three. The flexible twist-boat conformation of the cyclohexa-1,3-diyl possesses intermediate lifetime. Other than such conformational effects, it is difficult to rationalize the lifetimes of these rather similar 1,3-diradicals.
为了探索甲基取代在自由基位点和环大小的影响,从各自的偶氮烷烃中生成 1,3-双自由基并定量测定氧捕获。分子力学计算表明,在最低能量构象中,轨道间角约为。1,3-双基分别为 0/sup 0/、45/sup 0/ 和 60/sup 0/。因此,对于平面 cyclopenta-1,3-diyl(平面性证实为 ESR)系统间交叉自旋轨道耦合应该是最困难的,因此它应该具有相对较长的三重态寿命。相比之下,刚性褶皱双环(2.2.1)hepta-2,7-diyl 应该是三者中寿命最短的物种。cyclohexa-1,3-diyl 的灵活扭船构象具有中等寿命。除了这种构象效应,