Spectroscopic studies, density functional theory calculations, non-linear optical properties, biological activity of 1-hydroxy-4-((4-(N-(pyrimidin-2-yl)sulfamoyl)phenyl)diazenyl)-2-naphthoic acid and its chelates with Nickel (II), Copper (II), Zinc (II) and Palladium (II) metal ions

Abstract

Novel Nickel (II), Copper (II), Zinc (II) and Palladium (II) chelates with 1‑hydroxy-4-((4-(N-(pyrimidin-2-yl)sulfamoyl)phenyl)diazenyl)-2-naphthoic acid (H3L) have been produced and clarified using several physicochemical techniques. Quantum mechanical calculations of energies, geometries were achieved by using the density functional theory with Becke's three parameter exchange functional, the Lee_Yang_Parr correlation functional (B3LYP/GEN) combined with 6.311 G (d,p) and LANL2DZ basis sets. The analyses of Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) have been used to justify the charge transfer within the ligand and its chelates. The considered small energy gap between Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies expressions that the charge transfer occurs within the ligand and its chelates. The results show that the azo dye ligand exists in two tautomeric structures, the first structure (H3L), the sulphonamide (SO2NH), while the second one, the sulphonamide group in enolic form (H2L-OH). The H2L-OH tautomer has energy of 12.93 kcal/mol higher than that of H3L. The structure of H3L was found to be the most stable and used as the ligand in this study. The bond lengths of Ni(II) ion with the donating sites of the ligand in Ni-(H2L)2 chelate suggest a distorted octahedral geometry, Cu2-(L) chelate, suggests a highly distorted tetrahedral geometry, Zn-(HL) chelate displays a distorted octahedral geometry, Pd-(H2L) chelate approves a distorted square planar geometry around its own central metal ion. Geometrical parameters, molecular electrostatic potential maps and total electron densities analyses of the ligand and its chelates have been carried out. Molecular stability, hyper conjugative interactions, intramolecular charge transfer and bond strength have been examined by applying of natural bond orbital (NBO) analysis. Total static dipole moment, mean polarizability, anisotropy of the polarizability, mean first-order hyperpolarizability have been also achieved. From the molecular hyperpolarizability (˂β˃), The computed (˂β˃) values show that for the ligand (H3L) and its Ni-(H2L)2, Cu2-(L), Zn-(HL) and Pd-(H2L) are ~23, ~70, ~44, ~132 and ~38 times greater than that of Urea, indicating all the studied ligand and its chelates reveal significant polarizability and first-order hyperpolarizability and are predicted to be successful for Non-Linear Optical (NLO) materials. The analyses of the chelates indicate that the Zn(II) and Pd(II) form 1:1, Ni(II) form 1:2 while Cu(II) ion form 2:1 (M:L) and non-electrolytic behavior of chelates indicate the absence of counter ion. Ni-(H2L)2 complex had zero antibacterial activity against E. coli while its activity is higher than the azo dye against Staphylococcus aureus. Pd-H2L complex had almost the same activity as the azo dye against both types of bacteria. The higher activity of Zn-HL and Cu2-L complexes can be explained by their chelation.