Exploration of the Interaction Strength at the Interface of Anionic Chalcogen Anchors and Gold (111)-Based Nanomaterials

Abstract

Nowadays, the use of sulfur-based ligands to modify gold-based materials has become a common trend. Here, we present a theoretical exploration of the modulation of the chalcogenides-gold interaction strength, using sulfur, selenium, and tellurium as anchor atoms. To characterize the chalcogenide-gold interaction, we designed a nanocluster of 42 gold atoms (Au₄₂) to model a gold surface (111) and a series of 60 functionalized phenyl-chalcogenolate ligands to determine the ability of electron-donor and -withdrawing groups to modulate the interaction. The analysis of the interaction was performed by using energy decomposition analysis (EDA), non-covalent interactions index (NCI), and natural population analysis (NPA) to describe the charge transfer processes and to determine data correlation analyses. The results revealed that the magnitudes of the interaction energies increase following the order S < Se < Te, where this interaction strength can be augmented by electron-donor groups, under the donor-acceptor character the chalcogen-gold interaction. We also found that the functionalization in meta position leads to better control of the interaction strength than the ortho substitution due to the steric and inductive effects involved when functionalized in this position.

Keywords: chalcogenides; gold; noncovalent Interaction; supramolecular chemistry.

Figure 1

Schematic representation of the gold molecular system and the ligands used to model the gold-chalcogen interaction. The chalcogen atoms are represented by the sphere in cyan and it is pictured in the ortho substituted system (left) and meta substituted (right).

Figure 2

Graphic representation of the principal geometric parameters obtained for the systems with the substituent R in the ortho and meta positions (hydrogen-white, carbon-grey, gold-yellow and orange, chalcogen-cyan).

Figure 3

Plot of the interaction energies of the phenyl-chalcogenolates functionalized in meta (left) and ortho (right) positions versus the Hammett sigma constants σ_meta and σ_ortho.

Figure 4

Graphical representation of the non-covalent interactions between the gold substrate and the phenyl-sulphonate ligands functionalized in ortho with –NO₂ and NH₂ substituents. (hydrogen—white; carbon—grey; sulfur—yellow; nitrogen—blue and the isovalue used as cutoff was defined at 0.5).

Figure 5

Comparison of the different components to the covalent contribution to the interaction energies obtained from the energy decomposition analysis of ortho and meta substituted ligands with –NH₂, –OCH₃, –CN, and –NO₂ as functional group.

Figure 6

Plot of the amount of charge transferred to the gold substrate from the phenyl-chalcogenolates functionalized in meta (left) and ortho (right) positions.

Figure 7

Representation of the systems used to assess the effect in the interaction energy of multi-substitution of phenyl-selenophenolate ligands with two and three NH₂ functional group.