Brooks Claudine A, Doherty Andrew P
School of Chemistry, David Keir Building, Queen's University, Belfast, Northern Ireland BT9 5AG, UK.
J Phys Chem B. 2005 Apr 7;109(13):6276-9. doi: 10.1021/jp040554e.
The sequential two-electron reduction of benzaldehyde to the radical anion and dianion species in 1-butyl-3-methylimidazolium triflimide and 1-butyl-1-methylpyrrolidinium triflimide is reported. In 1-butyl-1-methylpyrrolidinium triflimide, the heterogeneous electrochemistry and follow-up chemical reactivity are essentially equivalent to that in conventional molecular-solvent-based electrolytes where no interaction with the media is observed. In 1-butyl-3-methylimmidazolium triflimide, reduction occurs via the same two heterogeneous processes; however, the apparent heterogeneous rate constants are smaller by ca. 1 order of magnitude which leads to quasi-reversible electrochemical behavior. Since the bulk viscosities of the liquids are similar, the slower heterogeneous kinetics are attributed to local interfacial viscosity due to local ordering in the imidazolium-based medium. Also, a dramatic anodic shift in the reduction potentials is observed in 1-butyl-3-methylimidazolium triflimide media that is attributed to a stabilizing interaction of the radical anion and dianion species with the imidazolium cation.
据报道，在1-丁基-3-甲基咪唑三氟甲磺酰亚胺和1-丁基-1-甲基吡咯烷三氟甲磺酰亚胺中，苯甲醛依次进行两电子还原生成自由基阴离子和二价阴离子物种。在1-丁基-1-甲基吡咯烷三氟甲磺酰亚胺中，异相电化学和后续化学反应本质上与传统分子溶剂基电解质中的情况相当，在传统电解质中未观察到与介质的相互作用。在1-丁基-3-甲基咪唑三氟甲磺酰亚胺中，还原通过相同的两个异相过程发生；然而，表观异相速率常数小约1个数量级，这导致了准可逆的电化学行为。由于两种液体的本体粘度相似，较慢的异相动力学归因于基于咪唑鎓的介质中局部有序排列导致的局部界面粘度。此外，在1-丁基-3-甲基咪唑三氟甲磺酰亚胺介质中观察到还原电位发生了显著的阳极偏移，这归因于自由基阴离子和二价阴离子物种与咪唑鎓阳离子之间的稳定相互作用。
