Solvatochromic, spectroscopic, DFT calculations, antimicrobial and docking studies of new Fe(III), Co(II), and Ni(II) chelates containing 1,2,4-triazine

Abstract

Abstract This study presents the synthesis and characterization of three novel metal chelates: Ni(DTHMN) ( 1 ), Co(DTHMN) ( 2 ), and Fe(DTHMN) ( 3 ). Comprehensive analytical techniques, including elemental analysis, infrared (IR) and electronic (UV-Vis) spectroscopy, thermal analysis, molar conductivity, and magnetic susceptibility measurements, were employed to investigate their structural and electronic properties. The findings indicate that the ligand DTHMN acts as a tridentate donor, coordinating through the hydroxyl group (O–H), azomethine nitrogen (C = N), and triazine nitrogen atoms, forming mononuclear chelates with tetrahedral or octahedral geometries. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed that the Ni(DTHMN) chelate adopts a nano-spherical to cubic morphology. All synthesized chelates exhibit luminescence behavior, suggesting potential utility in photoactive materials. Solvatochromic shifts in absorption and fluorescence spectra were analyzed to estimate ground-state (µ g ) and excited-state (µ e ) dipole moments. These were determined using Reichardt’s solvent polarity parameter (E T N ) and multiple empirical functions, including the Bilot–Kawski, Lippert–Mataga, Bakhshiev, and Kawski–Chamma–Viallet models. A notable increase in dipole moment upon excitation suggests enhanced stabilization of the excited state in polar solvents, particularly involving n–π* transitions. Density Functional Theory (DFT) calculations, performed using the B3LYP/GENECP method with a 6-311G(d, p) basis set for non-metal atoms and SDD for metal atoms, supported experimental data and provided insights into optimized structural parameters. Further computational analyses included molecular electrostatic potential (MEP) mapping and nonlinear optical (NLO) property evaluation, revealing charge distribution and optical characteristics. The antimicrobial activity of the complexes was tested against a panel of Gram-positive, Gram-negative bacteria, and fungi, showing promising efficacy. Finally, molecular docking studies were conducted to investigate the binding interactions of the chelates with the FabH–CoA enzyme complex (PDB ID: 1HNJ), providing insight into their potential as bioactive agents.