Synthesis, spectroscopic characterization, DNA interaction and antibacterial study of metal complexes of tetraazamacrocyclic Schiff base

The template condensation reaction between benzil and 3,4-diaminotoulene resulted mononuclear 12-membered tetraimine macrocyclic complexes of the type, [MLCl2] [M = Co(II), Ni(II), Cu(II) and Zn(II)]. The synthesized complexes have been characterized on the basis of the results of elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz. FT-IR, 1H and 13C NMR, FAB mass, UV–vis and EPR. An octahedral geometry has been envisaged for all these complexes, while a distorted octahedral geometry has been noticed for Cu(II) complex. Low conductivity data of all these complexes suggest their non-ionic nature. The interactive studies of these complexes with calf thymus DNA showed that the complexes are avid binders of calf thymus DNA. The in vitro antibacterial studies of these complexes screened against pathogenic bacteria proved them as growth inhibiting agents.

Graphical abstractComparison of zone of inhibition (in mm) of macrocyclic complexes with standard antibiotic against gram negative bacterial stains. Gentamicin-standard antibiotic.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► 12-Membered tetraazamacrocyclic complexes synthesized via template condensation. ► Characterized by physico-chemical methods and various spectroscopic techniques. ► All the complexes exhibit significant binding to CT-DNA. ► Antibacterial screening of the complexes proved them potent growth inhibitors.