Synthesis of Schiff base ligand from N-substituted benzenesulfonamide and its complexes: Spectral, thermal, electrochemical behavior, fluorescence quenching, in vitro-biological and in-vitro cytotoxic studies

Convenient synthesis of new octahedral complexes from 4-amino-N-(1,3-thiazol-2-yl) benzenesulfonamide and 2-hydroxybenzaldehyde with the molecular formula [M(L)2Cl2] (where M = Mn(II), Co(II) and Cu(II) ions) have been described. The Schiff base behaves as a bidentate ligand with oxygen and nitrogen donors and coordinates via phenolic oxygen and azomethine nitrogen. Structural features and bonding mode of the Schiff base have been proposed by magnetic properties and spectral methods. All the complexes exhibit d-d transitions, photo emissive and one electron quasi reversible redox behavior. The Schiff base ligand and its complexes have been screened for antimicrobial screening towards some clinically important microorganisms. The quenching studies were carried out for the [Cu(L)2Cl2] complex by the alizarin red S dye in DMSO using fluorescence measurements. The thermodynamic parameter ΔGet to predict feasibility of the transfer of electrons in the excited state was evaluated by employing the well-known Rehm-Weller expression. The evaluated highly biologically active complex [Cu(L)2Cl2] shows excellent cytotoxicity towards (MCF -7) cancer cell line. [Display omitted] •The mode of bonding between the central metal atom and the ligand reveals bidentate mode of bonding. The binding sites are azomethine and phenolic OH group., with distorted octahedral environment.•The synthesised complexes exhibits d-d transition, photo emission and one electron quasi reversible redox behaviour.•The thermodynamic feasibility of the excited state electron transfer reactions was calculated by employing the well-known Rehm-Weller expression shows the electron transfer process is thermodynamically favourable.•The excited state interaction of [Cu(L)2Cl2] complex with alizarin red S dye was carried out through fluorescence measurements.•The better cytotoxicity activity of Co (II) complex against MCF-7 cell line may play a significant role in metallo drug formulation.