Coordination Modes of Hydroxamates in Neptunium (V) Complexes in Aqueous Solution. Issue 9 (24th March 2017)

• Record Type: Journal Article
• Authors: Dumpala, Rama Mohana Rao; Rawat, Neetika; Bhattacharya, Arunasis; Tomar, Bhupendra Singh
• Is Part Of: ChemistrySelect. Volume 2:Issue 9(2017)
• Page Start: 2722
• Page End: 2731
• Publication Date: 2017-03-24
• Subjects: Complexation -- Coordination modes -- DFT calculations -- Hydroxamates -- Neptunyl -- Potentiometry -- Protonation -- Spectrophotometry; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201700031
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: A theoretical study to understand molecular structures and coordination modes of neptunium complexes with three different substituent hydroxamates viz., acetohydroxamate (AHA), benzhydroxamate (BHA) and salicylhydroxamate (SHA) was carried out using density functional theory (DFT). The geometries for different complexes reported in literature Mx Ly Hz (x:y:z) viz 1:1:1, 1:2:2 and 1:2:0 were optimized and interaction energies (ΔE) for complexation process were calculated to obtain the most probable structures of complexes. The ΔE value revealed, the complex stability order as NpO2 + ‐SHA > NpO2 ‐AHA > NpO2 ‐BHA which is in agreement with the reported experimental data. Higher negative charge on AHA compared to BHA leads to its higher interaction with NpO2 which in turn reflects in shorter Np‐Oeq (ligand) bond distances. In 1:1:1 complex of NpO2 ‐SHA, the binding mode involving ortho hydroxyl group and ‐NHO − oxygen atom (seven membered ring) shows most negative interaction energy.However, for binding of second ligand in 1:2:2 NpO2 ‐SHA complex, steric effects dominate and the mode involving five membered ring through oxygen atoms of ‐CONHO − is most stable. Abstract : Hydroxamates having three coordinating atoms can bind the metal atom through various modes involving different combinations of bidenticity. The hydroxamates with additional functional groups further enhance the number of possible coordination modes and even the atoms bonding to metal ion can change with ligand substituents and stoichiometry of the complex. The picture describes the possible modes of binding of aqua neptunyl ion with the salicylhydroxamate.