Structure, stability and energetics of ionic arsenic–water complexes

Abstract

The structure, stability and energetics of ionic arsenic–water complexes [As³⁺–nH₂O (n = 1–5) and As⁵⁺–nH₂O (n = 3–5)] have been studied in detail using the MP2 method. Both the trivalent and pentavalent ionic states of arsenic were considered. The change in binding energy of the complexes with increasing number of water molecules was investigated. For both complexes involving trivalent and pentavalent arsenic, highly intense modes are observed in the high-frequency region. The structure and symmetry of the complexes with increasing number of water molecules is discussed. The charge transfer in these complexes is illustrated with the help of the natural electron configuration. Both donation and back-donation processes involving the orbitals of oxygen and arsenic are analysed to explain the charge transfer.

Keywords:

• trivalent arsenic
• pentavalent arsenic
• structure
• symmetry
• charge transfer
• ab initio method

Acknowledgements

S. Bagchi thanks the Netaji Subhash Engineering College, Garia, Kolkata, India, for allowing him to carry out his research at IACS. I. Bhattacharyya thanks the Birbhum Institute of Engineering and Technology, Suri, Birbhum, India, for allowing him to pursue his research at IACS. B. Mondal is grateful to the Council of Scientific and Industrial Research (CSIR), Government of India, for providing a fellowship. Thanks are due to the reviewer for his constructive comments to improve the manuscript.