Template synthesis and spectroscopic characterization of 16-membered [N₄] Schiff-base macrocyclic complexes of Co(II), Ni(II), Cu(II), and Zn(II): in vitro DNA-binding studies

Abstract

Template condensation between o-phthalaldehyde and 3,4-diaminotoluene resulted in mononuclear 16-membered tetraimine macrocyclic complexes, [MLCl₂] [M = Co(II), Ni(II), Cu(II), and Zn(II)]. The proposed stoichiometry and the nature of the complexes have been deduced from elemental analyses, mass spectra, and molar conductance data. The macrocyclic framework has been inferred from ν(C=N) and ν(M–N) bands in the IR spectra and the resonances observed in ¹H and ¹³C-NMR spectra. Octahedral geometry has been assigned for all these complexes on the basis of position of the bands in electronic spectra and magnetic moment data; distorted octahedral geometry has been assigned for the Cu(II) complex on the basis of EPR data. The low-conductivity data of all the complexes suggest their non-ionic nature. Interaction of these complexes with calf-thymus DNA (CT DNA) has been examined with fluorescence quenching experiments, which show that the complexes are avid binders of CT DNA.

Keywords:

• Macrocycles
• Schiff bases
• Spectral studies
• Template synthesis

Acknowledgments

The Chairman, Department of Chemistry, Aligarh Muslim University, Aligarh, India, is acknowledged for providing necessary research facilities. The authors thank University Grants Commission, New Delhi, for the financial support.