Structural investigations, DFT, anti-oxidant and α-amylase inhibitory activity of metal complexes of benzothiazole based hydrazone

The present manuscript describes the synthesis, spectral characterisation, DFT studies and biological activity of a series of 3d transition metal complexes of (E)-2-((2-(benzo[d]thiazole-2-yl)hydrazono)methyl)-5-(diethylamino)phenol (L1) in (1:1) and (1:2) ratio. Various spectral analysis revealed the presence of ONN binding domain in L1. The elemental composition was confirmed using mass spectrometry technique. The stability of the geometry was also confirmed with DFT based method using B3LYP/LanL2Dz level of theory. Absence of any imaginary frequency revealed the presence of geometry on global minima of potential energy surface. Job’s plot confirm the stoichiometric ratio of metal complexes. Electrochemical behaviour (cyclic voltammetry), magnetic moment and Conductance measurements were also investigated for the metal-complexes. Kinetic parameters for different stages of thermal decomposition of metal complexes were calculated by using Coats–Redfern and Broido method. Positive free-energy of decomposition describes the non-spontaneous nature of thermal decomposition. The negative ΔS value observed for metal complexes under consideration reveals the ordered arrangement of metal complexes than their reactants. The octahedral environment of Co²⁺, Ni²⁺, Cu²⁺ and Cd²⁺ complexes was elucidated with the help of spectroscopic data. The ligand (L1) and its metal complexes (M1–M8) exhibited excellent α-amylase and moderate anti-oxidant activities. Maximum α-amylase inhibition was exhibited by M7 with a percentage inhibition of 96.65% (IC₅₀ = 0.070 µM) and the lowest by M1 (87.00%, IC₅₀ = 0.086 µM).