State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun, Jilin 130022, China.
University of Chinese Academy of Sciences , Beijing 100039, China.
Langmuir. 2016 Nov 8;32(44):11514-11519. doi: 10.1021/acs.langmuir.6b03206. Epub 2016 Oct 21.
Electroreduction of aryl diazonium salts on gold can produce organic films that are more robust than their analogous self-assembled monolayers formed from chemical adsorption of organic thiols on gold. However, whether the enhanced stability is due to the Au-C bond formation remains debated. In this work, we report the electroreduction of an aryl diazonium salt of 4,4'-disulfanediyldibenzenediazonium on gold forming a multilayer of Au-(Ar-S-S-Ar), which can be further degraded to a monolayer of Au-Ar-S by electrochemical cleavage of the S-S moieties within the multilayer. By conducting an in situ surface-enhanced Raman spectroscopic study of both the multilayer formation/degradation and the monolayer reduction/oxidation processes, coupled to density functional theory calculations, we provide compelling evidence that an Au-C bond does form upon electroreduction of aryl diazonium salts on gold and that the enhanced stability of the electrografted organic films is due to the Au-C bond being intrinsically stronger than the Au-S bond for a given phenylthiolate compound by ca. 0.4 eV.
芳基重氮盐在金上的电化学还原可以产生比其类似的通过有机硫醇在金上的化学吸附形成的自组装单层更稳定的有机膜。然而，增强的稳定性是否归因于 Au-C 键的形成仍存在争议。在这项工作中，我们报告了芳基重氮盐 4,4'-二巯基二苯二氮烯盐在金上的电化学还原，形成了 Au-(Ar-S-S-Ar) 的多层结构，通过电化学断裂多层结构中的 S-S 部分，可以进一步降解为单层的 Au-Ar-S。通过对多层形成/降解以及单层还原/氧化过程进行原位表面增强拉曼光谱研究，并结合密度泛函理论计算，我们提供了令人信服的证据，证明芳基重氮盐在金上的电化学还原确实会形成 Au-C 键，并且电接枝有机膜的增强稳定性是由于 Au-C 键比给定的苯基硫醇化合物的 Au-S 键本质上强约 0.4 eV。
