Theoretical study of the optimal As(OH)3-H2O complex: Interaction energy and topological analysis of the electronic density

We present a detailed theoretical study of the interaction of arsenious acid with a water molecule, for which a singular triply hydrogen-bonded complex is found. We focus on the accurate determination of the interaction energy and analyze the electronic density and atomic charges through the Atoms-in-Molecules (AIM) topological approach of Bader. Our benchmark-quality interaction energy is 10.68 kcal/mol. AIM analysis shows three intermolecular bond critical points confirming the hydrogen bonds. We find that this triply hydrogen-bonded complex is quite energetic considering the double acceptor character of oxygen of the water molecule compared to other triply hydrogen-bonded structures. AIM atomic charges show that the fragments are neutral in the complex, thus revealing the dominant dipole-dipole nature of the intermolecular interaction.