Tailoring the electronic properties among oxoarsine, arsinoyl and arsine oxide isomers: the simplest molecular systems with an arsenic–oxygen bond

Abstract

The main goal of this investigation is to understand the reaction pathways and the electronic and spectroscopy properties of AsOH_n radicals (n = 0–3), which are some of the simplest compound models with an arsenic–oxygen bond. A CCSD(T) level of theory with a complete basis set limit (CBS) was applied to understand the relative stability and the reaction pathways among the isomers. Several reaction pathways such as the unimolecular rearrangement routes, the internal rotational transition state structures, and the hydrogen release routes were also evaluated among these structures. In the case of oxoarsine isomers, it was seen that the oxoarsine (HAsO) ground state structure presents a singlet state and AsOH possesses a triplet ground one. trans-Hydroxyarsinyl (trans-HAsOH) is the global minimum structure with an energy gap around 20 kcal mol⁻¹ when compared with arsinoyl (H₂AsO), and this energy difference is increased two times when compared with AsOH₂. Arsinous acid (H₂AsOH) is more stable than arsine oxide (H₃AsO) based on the relative energy difference, while it is predicted that there is a large energy gap when compared with HAs(H₂O) stereoisomers. The heat of formation was also calculated for each isomer. In addition, in the characterization of arsenic–oxygen bond characters, several bond order indexes and different population methods were also applied to understand the influence of different methodologies, as well as the Quantum Theory of Atoms in Molecules (QTAIM) and the Natural Bond Orbital (NBO) method.