Tetraaza macrocyclic Schiff base metal complexes bearing pendant groups: Synthesis, characterization and bioactivity studies

We report a new tetraaza macrocyclic Knoevenagel Schiff base as the 13-membered ligand developed by non template route via condensation of 3-(cinnamyl)-pentane-2,4-dione with two equivalent of 4-aminoantipyrine as pendant group prior to its execution for Knoevenagel condensation with o-phenylenediamine. The above type of conjugate macrocyclic ligand tends to employ as a potential tetradentate ligand, which generated a seies of macrocyclic metal complexes (1-4) with Cu(II), Co(II), Ni(II) and Zn(II) metal ions. Herein, the macrocyclic ligand and its metal complexes were characterized by the spectral and analytical methods including UV-vis, FTIR, C-13 and H-1 NMR, ESI-MS, EPR, microanalytical and magnetic moment values. The above set of data tend to suggest that synthesized metal complexes exist in square planar geometry, whereas high molar conductance values supported about the distribution of complexes in ionic nature. Indeed, cyclic voltammetry and optical absorption titration as well as hydrodynamic experiments and docking analysis data were used to identiy the way of binding of these metal complexes with calf thymus deoxyribonucleic acid as intercalation type. Further, DNA damage study was conducted by gel electrophoresis. Moreover, these complexes were studied for antimicrobial screening under in vitro condition against a set of microorganisms via broth dilution technique. It was noted that all the complexes occurred to reveal better activity as compared to macrocyclic Schiff base ligand. Also, the cancer cell lines including cervical, epithelioma, human breast and cell line of normal human dermal fibroblast were chosen to assess for cytotoxic effect with above samples.