Aminothiazole-Linked Metal Chelates: Synthesis, Density Functional Theory, and Antimicrobial Studies with Antioxidant Correlations.

During the current study, the new aminothiazole Schiff base ligands ( S 1 ) and ( S 2 ) were designed by reacting 1,3-thiazol-2-amine and 6-ethoxy-1,3-benzothiazole-2-amine separately with 3-methoxy-2-hydroxybenzaldehyde in good yields (68-73%). The ligands were characterized through various analytical, physical, and spectroscopic (FT-IR, UV-Vis, 1 H and 13 C NMR, and MS) methods. The ligands were exploited in lieu of chelation with bivalent metal (cobalt, nickel, copper, and zinc) chlorides in a 1:2 (M:L) ratio. The spectral (UV-Vis, FT-IR, and MS), as well as magnetic, results suggested their octahedral geometry. The theoretically optimized geometrical structures were examined using the M06/6-311G+(d,p) function of density function theory. Their bioactive nature was designated by global reactivity parameters containing a high hardness (η) value of 1.34 eV and a lower softness (σ) value of 0.37 eV. Different microbial species were verified for their potency ( in vitro ), revealing a strong action. The Gram-positive Micrococcus luteus and Gram-negative Escherichia coli gave the highest activities of 20 and 21 mm for compounds ( 8 ) and ( 7 ), respectively. The antifungal activity against the Aspergillus niger and Aspergillus terreus species gave the highest activities of 20 and 18 mm for compounds ( 7 ) and ( 6 ), respectively. The antioxidant activity, evaluated as DPPH and ferric reducing power, gave the highest inhibition (%) as 72.0 ± 0.11% (IC 50 = 144 ± 0.11 μL) and 66.3% (IC 50 = 132 ± 0.11 μL) for compounds ( 3 ) and ( 8 ), respectively. All metal complexes were found to be more biocompatible than free ligands due to their chelation phenomenon. The energies of LUMOs had a link with their activities.