Evidence for Significant Through-Space and Through-Bond Electronic Coupling in the 1,4-Diphenylcyclohexane-1,4-diyl Radical Cation Gained by Absorption Spectroscopy and DFT Calculations
作者:Hiroshi Ikeda、Yosuke Hoshi、Hayato Namai、Futoshi Tanaka、Joshua L. Goodman、Kazuhiko Mizuno
DOI:10.1002/chem.200700820
日期:2007.11.16
formation of an intense electronic absorption band at 476 nm, which is attributed to the 1,4-diphenylcyclohexane-1,4-diyl radical cation. The absorption maximum (lambda(ob)) of this transient occurs at a longer wavelength than is expected for either the cumyl radical or the cumyl cation components. Substitution at the para positions of the phenyl groups in this radical cation by CH(3)O, CH(3), F, Cl
N-甲基喹啉四氟硼酸酯/联苯的光敏单电子转移促进了2,5-二苯基-1,5-己二烯的氧化,在476 nm处形成强烈的电子吸收带,这是由于1,4-二苯基环己烷-1,4-二基自由基阳离子。此瞬态的最大吸收值(λ(ob))发生在比对枯基自由基或对枯基阳离子组分预期的更长的波长处。CH(3)O,CH(3),F,Cl和Br取代该自由基阳离子中苯基的对位会导致lambda(ob)的红移越来越大。比较Rho值,该值是从自由基阳离子相对于sigma(+)的电子跃迁能的Hammett图获得的,与对枯基阳离子的对数的关系表明,取代基对1,4-二芳基环己烷-1,4-二基自由基阳离子的跃迁能的影响约占对对枯基阳离子跃迁能的影响的一半。观察到的取代基引起的lambda(ob)的红移和lambda(ob)对取代基变化的降低的敏感性是根据以下建议:在异丙基的枯基和枯基阳离子部分之间存在明显的贯穿空间和-键电子相互作用。 1