Argon Adsorption on Cationic Gold Clusters Aun+ (n ≤ 20).

Piero Ferrari,Ewald Janssens

doi:10.3390/molecules26134082

Abstract

The interaction of Aun+ (n ≤ 20) clusters with Ar is investigated by combining mass spectrometric experiments and density functional theory calculations. We show that the inert Ar atom forms relatively strong bonds with Aun+. The strength of the bond strongly varies with the cluster size and is governed by a fine interplay between geometry and electronic structure. The chemical bond between Aun+ and Ar involves electron transfer from Ar to Au, and a stronger interaction is found when the Au adsorption site has a higher positive partial charge, which depends on the cluster geometry. Au15+ is a peculiar cluster size, which stands out for its much stronger interaction with Ar than its neighbors, signaled by a higher abundance in mass spectra and a larger Ar adsorption energy. This is shown to be a consequence of a low-coordinated Au adsorption site in Au15+, which possesses a large positive partial charge.

Highlights

As a bulk material, gold is the noblest of all metals [1]
We address the interaction between Aun + clusters with Ar, by performing density functional theory calculations in the extended n ≤ 20 size range, in combination with mass spectrometric experiments
We demonstrate the formation of a chemical bond between Ar and the clusters, which is a consequence of an electron charge donation from Ar to Au

Summary

Introduction

Gold is the noblest of all metals [1]. At the nanoscale, gold becomes reactive towards several molecules, and can selectively catalyze certain reactions, which has attracted broad scientific attention [2,3,4,5]. Pyykkö, who in 1995 proposed that the bond between Au+ ions with different noble gases (Ng = Ar, Kr, Xe) has a partially covalent character, and cannot merely be ascribed to the expected weak dispersion forces [7]. While this claim was controversial at that time [8,9,10], it is nowadays accepted, and noble gas chemistry has become an active research field, with Au-based systems drawing significant attention [6,11]

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