Molecular interaction study of formohydroxamic acid (FHA) with water

Abstract

Ab initio and dft theoretical methods have been used to study the hydrogen bonding in the complexes formed between formohydroxamic acid (FHA) and water molecules. Eight reasonable geometries on the potential energy surface of formohydroxamic acid and water systems have been considered; four structures with three water molecules FHA-(H 2O) 3 and four structures with two water molecules FHA-(H 2O) 2. In all the complexes, the formohydroxamic acid has cis-keto form. The most stable complexes were found with cyclic double hydrogen bonds. The results of chemical hardness indicate that it does not obey maximum hardness principle (MHP) for the above hydrogen bonded systems. Two-body, three-body interaction energies and relaxation energies have been calculated by applying many-body analysis to know their role in the total interaction energy of the molecule. The results of many body analysis indicate that two-body interaction energy contribute more to the total interaction energy when compared to three-body interaction energies. Topological analysis has been performed for the complexes using Bader's Atoms in molecule theory. The topological parameters electron density and Laplacian of electron density show excellent linear correlation with the hydrogen bond length. NBO analysis have been carried out to study the charge transfer between proton acceptor to the antibonding orbital of the X-H bond in the complexes.