On the kinetics and thermodynamics of S–X (X = H, CH3, SCH3, COCH3, and CN) cleavage in the formation of self-assembled monolayers of alkylthiols on Au(111)

Abstract

Abounding potential technological applications is one of the many reasons why adsorption of aliphatic thiols on gold surface is a subject of intense research by many research groups. Understanding and exploring the nature of adsorbed species, the site of adsorption and the nature of interaction between adsorbed species and the gold surface using experimental and theoretical investigations is an active area of pursuit. However, despite a large number of investigations to understand the atomistic structures of thiols on Au(111), some of the basic issues are still unaddressed. For instance, there is still no clear information about the mechanism of adsorption of alkylthiol on gold surface. Furthermore, the reactivity and mechanism of adsorption of alkylthiol is likely to differ when gold adatoms and/or vacancies in the gold layers are considered. In this work, we have tackled these issues by computing the stationary states involved in the thiols adsorption in order to shed light on the kinetics aspects of adsorption process. In this respect, we have considered a variety of thiols into consideration such as methylthiol, dimethylsulfide, dimethyldisulfide, thioacetates, and thiocyanates. We have also considered the cleavage mechanism in the clean and the reconstructed surface scenario and the structure, energetics and spin densities have been computed using electronic structure calculations. For all the studied cases, an homolytic cleavage of CH 3 S-X (X = H, CH 3 , SCH 3 , CN, and COCH 3 ) bond has been found to occur upon adsorption on the gold surface.

Chemisorption of nitronyl–nitroxide radicals on gold surface: an assessment of morphology, exchange interaction and decoherence time

“…This is consistent with the observation of the Kondo effect in the weak coupling regime 49 for a different nitronyl-nitroxide radical on Au(111) where the magnetic impurities could be injected directly by the Nit itself through the homolytic break of the -S-Ac in the conduction bands as already suggested previously. 45,46,50,51 Therefore, a magnetic interaction between impurities leading to magnetic ordering may arise 52 if the spin correlation generated by the radical-conduction electrons is preserved by the electrons which then interact with the other radical. This interaction is therefore expected to be strongly dependent on the temperature, if thermal relaxation processes can interfere in the transfer of the spin correlation.…”

Single molecule magnets grafted on gold: magnetic properties from ab initio molecular dynamics

“…22,23 The Fe 4 C 5 molecule has two side chains, each containing one thioacetyl group. Each layer consists of 80 gold atoms.…”

“…From experimental and computational evidence, it can be determined that both thioacetyl and simple thiols undergo a homolithic cleavage of the S-Ac (S-H) bond leading to the formation of a sulfur radical, which is the species that effectively binds to the metallic substrate. 22,23 The Fe 4 C 5 molecule has two side chains, each containing one thioacetyl group. Thanks to the steric hindrance of the magnetic core, only one of the two chains can actually bind to the substrate.…”

Effect of cavitation intensity control on self-assembling of alkanethiols on gold in room temperature ionic liquids

“…Thiol groups exhibit very strong reactivity towards gold, while the SAMs obtained are very compact and organized. The mechanism of thiol grafting on gold consists in exothermical homolytic cleavage of S-H bond [15] , [16] with H 2 formation [17] . Nevertheless, to carry out grafting of well-organized and compact monolayers, long modification times are needed i.e.…”