Clean Water and Sanitation (SDG 6), Climate Action (SDG 13)
Metal ion (M 2+ ) detection in water promoted by metal-dimethylglyoxime pincer complexes: DFT, QTAIM, NBO and spectral properties (IR and UV-vis) Djendo Mazia, Suzane Leonie * , Ndom Jean Claude, Bikele Mama Désiré Computational and Theoretical Chemistry Unit, Department of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon. E-mail: bikelemama@yahoo.fr The examination of chelating properties to capture alkaline earth (Mg 2+ ), transition (Fe 2+ , Co 2+ , Ni 2+ , and Cu 2+ ), and post-transition (Zn 2+ , Sn 2+ , and Pb 2+ ) metal (M) ions by bis-dimethylglyoximato ligand using M06-2X/6-31G(d;p)/Lanl2DZ in DFT method. Our Geometrical results obtained indicate that O…O separation distance (upper than 2.5Å) increase along the series Ni < Sn < Co< Pb< Fe< Cu< Zn < Mg proved the asymmetric character of the two formed O–H…O intramolecular H-bonds within the complexes. Collectively, optimised molecular geometries of all complexes feature a metal centered in a square-planar environment Chelation of the glyoxime ligand entails formation of a five-membered metallacycle (two with the both oxime ligand and the two others from the hydrogen bridged formed) which adopts a perfectly planar conformation. This geometrical structure exhibits the presence of a centrosymmetric resulting from improper rotation S2v which interchanges group atom of each ligand through an average C 2v symmetry followed by a perpendicular σ-plan. According to A.Syed Yunus et al exceptional stability of these complexes can be accentuated to their planar structure. As earlier reported by L.E. Godycki et al, the presence of typically O---H−O hydrogen bonds (short H bond) coupled to the planar structural of M(Hdmg) 2 are responsible for the insolubility (or low solubility) in alkaline medium.The spectral properties (IR and UV-vis) calculation studied is to predict of metal detection and the possibility to remove it, the calculated DT-DFT in water as a solvent revealed the lowest-lying singlet→singlet electronic transitions involving bis-Hdmg and M 2+ that is governed by ILLCT for Mg 2+ , MLCT for, Fe 2+ , Ni 2+ , and Cu 2+ , and both MLCT and LMCT for Zn 2+ , Sn 2+ , and Pb 2+ complexes. DFT-calculated IR spectra in the gas phase demonstrated a correlation between a stronger O-H stretching mode and a weaker intramolecular H-bond interaction. The electronic calculated results based on bonding properties analysis according to QTAIM and NBO calculations reveal that, the nature of the metal as well as the presence of asymmetric intramolecular H-bond which connect the two Hdmg ligands in the completely planar molecules determine the chemical and thermodynamic stability. Key words: Chelating properties, bis-dimethylglyoximato ligand, stability, aqueous solution, alkaline earth, transition, and post-transition metal (M) ions. References 1. L. Tschugaeff, Ü ber ein neues, empfindliches Reagens auf Nickel. Ber. Dtsch. Chem. Ges. 1905, 38, 2520−2522. 2. A.Syed Yunus, K. Devendra Reddy, K. Arun Manna. Structural, Electronic, and Spectral Properties of Metal dimethylglyoximato [M(DMG)2; M = Ni 2+ , Cu 2+ ] Complexes: A Comparative Theoretical Study. J. Phys. Chem. A 123 (2019) 9166−9174 3. L.E. Godycki, R.E. Rundle, The structure of nickel dimethylglyoxime. Acta Crystallogr. 6 (1953) 487–495.
P53
© The Author(s), 2025
Made with FlippingBook Learn more on our blog