Abstract
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•Essential metal ion complexes of TCSA is reported.•TCSA-metal complexes have shown better antibacterial activity than TCSA itself.•Antibiotic and antioxidant activities of complexes were found related.•Studied compounds have shown an average protein binding ability.•The resolution of ambiguity of the structures was performed by the DFT calculations.•All the complexes seem to possess the square planar geometry.
Although, 3,5,6-Trichlorosalicylic acid (TCSA) does not show good antibacterial activity, but its metal complexes have shown better activity for the selected bacterial strains with good degree of selectivity. Amongst the eight synthesized essential metal complexes of TCSA, Mn(II)-TCSA and Ni(II)-TCSA have been found to be more effective with MIC range of 20–50µg/Las compared to control (chloramphenicol). The activity of an individual complex against different microbes was not identical, indicating the usage of an individual metal chelate against a targeted bacterial strain. Besides, the protein (BSA) binding constant of TCSA and its metal complexes were determined and ordered as Ca(II)-TCSA>Cu(II)-TCSA>Mg(II)-TCSA≫Mn(II)-TCSA≫Zn(II)-TCSA>>>Ni(II)-TCSA>>>Co(II)-TCSA>Fe(II)-TCSA>TCSA. The present study has confirmed enhanced antibacterial activity and binding constants for the metal chelates of TCSA in comparison to free TCSA, which seems directly related with the antioxidant activity of these complexes. Further, bearing the ambiguity related to the structural characterization of the metal complexed with TCSA ligand, DFT calculations have been employed as the tool to unravel the right environment around the metals, studying basically the relative stability of square planar and octahedral metal complexes of TCSA.