Mechanisms of metal ion-coupled electron transfer

• Published in: Physical chemistry chemical physics : PCCP 2012-01, Vol.14 (24), p.8472-8484
• Main Authors: Fukuzumi, Shunichi, Ohkubo, Kei, Morimoto, Yuma
• Format: Article
• Language: English
• Subjects: Anions; Binding; Chemistry; Electron transfer; Electron Transport; Exact sciences and technology; General and physical chemistry; Lewis acid; Lewis base; Metal ions; Metals - analysis; Metals - chemistry; Oxygen - chemistry; Physical chemistry; Porphyrins - chemistry; Quinones - chemistry; Radicals
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c2cp40459a

Redox inactive metal ions acting as Lewis acids can control electron transfer from electron donors (D) to electron acceptors (A) by binding to radical anions of electron acceptors which act as Lewis bases. Such electron transfer is defined as metal ion-coupled electron transfer (MCET). Mechanisms of metal ion-coupled electron transfer are classified mainly into two pathways, i.e. , metal ion binding to electron acceptors followed by electron transfer (MB/ET) and electron transfer followed by metal ion binding to the resulting radical anions of electron acceptors (ET/MB). In the former case, electron transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced electron-transfer reactions including back electron-transfer reactions. This article clarifies mechanisms of metal ion-coupled electron-transfer (MCET) reactions, which provide valuable insights into fine control of electron-transfer reactions by binding metal ions to radical anions of various electron acceptors.