Anion-dominated Redox Reaction of a SAM of an Alkylthiolated Viologen Bearing a Covalently-attached Intramolecular Sulfonate Group on a Gold Electrode (Supporting Information)

The redox processes of the self-assembled monolayers (SAMs) of alkylthiolated viologens on Au electrodes are largely determined by oxidation-state-dependent binding of electrolyte anions to the viologen moiety in an aqueous solution. In this paper, we give an answer to a question: what if the SAM-forming molecule has a covalently-attached intermolecular anionic site? We used the results of the voltammetric measurements for a SAM of a viologen with a covalently-attached sulfonate group, 1-(10-mercaptodecyl)-1′-(3-sulfonatopropyl)-4,4′-bipyridinium bromide (HS-C10-V-C3-SO3− bromide salt), and examined the effect of intramolecular ion binding on the redox behavior. We found the coexistence of two distinct types of redox couples: one with a viologen moiety, which binds always to the sulfonate group, and the other with a moiety, which catches and releases an electrolyte anion from the solution upon redox. We deciphered rather complicated behavior and discussed the implications.

在金电极上，自组装单分子层（SAMs）中烷基硫醇化紫罗兰的氧化还原过程主要受电解质阴离子与紫罗兰基团在水中氧化态依赖性结合所决定。本文针对一问题给出解答：若形成SAM的分子具有共价连接的分子间阴离子位点，将作何变化？我们利用了含有共价连接的磺酸基团的紫罗兰SAM（1-(10-巯基癸基)-1′-(3-磺酸基丙基)-4,4′-双吡啶溴化物，HS-C10-V-C3-SO3−溴化物盐）的电化学测量结果，考察了分子内离子结合对氧化还原行为的影响。我们发现了两种不同类型的氧化还原对共存：一种是与紫罗兰基团结合，始终与磺酸基团结合；另一种则能从溶液中捕获和释放电解质阴离子。我们解析了相对复杂的反应行为，并探讨了其意义。