posted on 2021-11-24, 16:37authored bySadaf Noreen, Sajjad H. Sumrra
During the current
study, the new aminothiazole Schiff base ligands
(S1) and (S2) 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, 1H and 13C 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% (IC50 = 144 ± 0.11 μL) and 66.3% (IC50 = 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.