Real-time mechanistic study of carbon nanotube anion functionalisation through open circuit voltammetry
Real-time mechanistic study of carbon nanotube anion functionalisation through open circuit voltammetry
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DOI：
10.1039/c8sc04970j
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发表时间：
2019-03-21
期刊：
影响因子：
8.4
通讯作者：
Shaffer, Milo S. P.
中科院分区：
文献类型：
--
作者：
Clancy, Adam J.;Sirisinudomkit, Pichamon;Shaffer, Milo S. P.
通过开路伏安法在整个反应过程中监测用有机溴化物官能化还原的单壁碳纳米管的机制，并通过一系列比较反应进一步阐明。的官能化程度映射对试剂的还原电位，取代基的电子捐赠程度（哈米特参数），和能量计算，从头算，解离和异裂的C-Br键。与先前假设的还原/均裂机制相反，该反应被证明是由碳-卤化物键与还原的纳米管作为复合物的快速缔合组成，取代表面凝聚的抗衡阳离子，导致净纳米管表面负电荷的初始增加。该复合物随后通过从还原的单壁碳纳米管到有机溴化物的电荷转移而缓慢降解，利用电荷，并且碳-卤化物键异相断裂。初始试剂中C-Br键上的电子密度是官能化程度的最佳预测因子，更多的供电子取代基增加官能化程度。OCV的机制和研究此类反应的新应用可能与广泛的相关系统相关。
The mechanism of the functionalisation of reduced single walled carbon nanotubes with organobromides was monitored by open circuit voltammetry throughout the reaction and further elucidated through a series of comparative reactions. The degree of functionalisation was mapped against the reagent reduction potential, degree of electron donation of substituents (Hammett parameter), and energies calculated, ab initio, for dissociation and heterolytic cleavage of the C-Br bond. In contrast to the previously assumed reduction/ homolytic cleavage mechanism, the reaction was shown to consist of a rapid association of carbon-halide bond to the reduced nanotube as a complex, displacing surfacecondensed countercations, leading to an initial increase in the net nanotube surface negative charge. The complex subsequently slowly degrades through charge transfer from the reduced single-walled carbon nanotube to the organobromide, utilizing charge, and the carbon-halide bond breaks heterolytically. Electron density on the C-Br bond in the initial reagent is the best predictor for degree of functionalisation, with more electron donating substituents increasing the degree of functionalisation. Both the mechanism and the new application of OCV to study such reactions are potentially relevant to a wide range of related systems.