A Mechanistic Dichotomy in Scandium Ion-Promoted Hydride Transfer of an NADH Analogue: Delicate Balance between One-Step Hydride-Transfer and Electron-Transfer Pathways
作者:Junpei Yuasa、Shunsuke Yamada、Shunichi Fukuzumi
DOI:10.1021/ja064708a
日期:2006.11.1
Sc3+-promoted electron transfer indicates that the reaction pathway is changed from one-step hydride transfer from AcrH2 to the TolSQ-Sc3+ complex to Sc3+-promoted electron transfer from AcrD2 to the TolSQ-Sc3+ complex, followed by proton and electron transfer. Such a change between two reaction pathways, which are employed simultaneously, is also observed by simple changes of temperature and concentration
氢化物从 NADH 类似物 9,10-二氢-10-甲基吖啶 (AcrH2) 转移到 1-(对甲苯基亚磺酰基)-2,5-苯醌 (TolSQ) 的速率常数 (kH) 随 Sc(3) 的增加而增加+) 浓度 ([Sc(3+)]) 达到恒定值,当所有 TolSQ 分子形成 TolSQ-Sc(3+) 复合物时。然而,当 AcrH2 被双氘化化合物 (AcrD2) 取代时,速率常数 (kD) 会随着 ([Sc(3+)]) 的增加而线性增加,而不会表现出饱和行为。在这种情况下,主要动力学氘同位素效应 (kH/kD) 随着 ([Sc(3+)]) 的增加而降低。另一方面,Sc(3+) 促进的从三(2-苯基吡啶)铱 [Ir(ppy)3] 到 TolSQ 的电子转移的速率常数也随着 ([Sc(3+)]) 的增加而线性增加由于在 TolSQ*- 和 Sc(3+) 之间形成 1:2 的复合物,导致高浓度的 Sc(3+),AcrH2