Size Matters, but Is Being Planar of Any Relevance? Electron Donor−Acceptor Properties of Neutral Gold Clusters up to 20 Atoms

The main goal of this investigation is to analyze the electron donor−acceptor properties of planar and three-dimensional gold clusters (Au N (with N = 2−20), and for this purpose, a new simple model based on density functional theory is used. Calculations at the B3LYP level permit us to determine the electrodonating (χ−) and electroaccepting (χ + ) electronegativity of Au N . On the basis of this analysis, it is possible to conclude that gold clusters with an odd number of atoms are better electron acceptors and better electron donors than clusters with an even number of atoms. Likewise, planar clusters are better electron acceptors than three-dimensional ones. These parameters are used to explain previous results concerning the reactivity of neutral clusters with O 2 and CO. The interaction of these neutral gold clusters with adenine−uracil (AU) and guanine−cytosine (GC) base pairs is also described. A rather particular correlation was found between χ+ or χ− and the binding energies, which indicates the usefulness of this simple model to anticipate the direction of the charge transfer process and to estimate the magnitude order of the binding energies. The relevance of being planar with reference to these results is also analyzed.