New hexadentate macrocyclic ligand and their copper(II) and nickel(II) complexes: Spectral, magnetic, electrochemical, thermal, molecular modeling and antimicrobial studies

Ni(II) and Cu(II) complexes were synthesized with a hexadentate macrocyclic ligand [3,4,8,9tetraoxo-2,5,7,10tetraaza-1,6dithio-(3,4,8,9) dipyridinedodecane(L)] and characterized by elemental analysis, molar conductance measurements, mass, NMR, IR, electronic, EPR spectral, thermal and molecular modeling studies. All the complexes are 1:2 electrolytes in nature and may be formulated as [M(L)]X2 [where, M = Ni(II) and Cu(II) and X = Cl−, NO3−, ½SO42−, CH3COO−]. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Ni(II) complexes and tetragonal geometry for Cu(II) complexes. The antimicrobial activities and LD50 values of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against two different species of bacteria and plant pathogenic fungi.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We have synthesized Schiff's base macrocyclic complexes. ► Characterized the ligand and complexes by IR, mass. NMR, UV, EPR, CV, TGA/DSC, etc. ► Molecular modeling has been provided. ► A distorted octahedral geometry has been assigned for Ni(II) and tetragonal geometry for Cu(II) complexes. ► Antimicrobial studies with LD50 values have been provided.