A theoretical study of the influence of gold nanoplatelets sites in C[sbnd]C coupling reaction

Abstract

The experimental evidences show that the nanoplatelets of 20 nm wide and 3−4 nm height, deposited on graphene promote Suzuki cross-coupling reactions. In this regard the adsorption and activation of halobenzene (C6H5Cl(Br/I)), of phenylboronic acid (C6H5B(OH)2) and the formation of biphenyl (C6H5-C6H5) molecules on surfaces that simulates the facets and edges of the gold nanoplatelets, were investigated by means of DFT calculations. The activation and reaction energies of halobenzene molecules are the lowest on the edge between (111)/(100) facets, but even so for C-Cl is relatively high. On all surfaces the energies decrease with decreasing the C–X bond strengths. Therefore, for CI bond the dissociation is possible also on (111), (100) and the edge between (111)/(111) facets. The phenylboronic acid dissociates easily on all surfaces in the presence of adsorbed hydroxyl fragments. The CC coupling between two phenyl (C6H5) fragments is the least sensitive to the type of sites, being the rate determining step, competing with C-Cl dissociation. The strong adsorption energy of KI molecule indicate possible poisoning of the (111)/(100) edge and of the (111) facet. Overall the studies show a probability of the reaction to take place especially on the edge between (111)/(100) microfacets. If some of the reactions steps are straightforward predicted to take place on the nanoplatelets sites, the reaction steps with higher activation energies are expected to be influenced also by other parameters such as interfaces between nanoplatelets and graphene and which are intended to be studied separately.