Synthesis, characterization, catalytic, antimicrobial, DNA binding and cleavage studies of N-functionalized tetraazamacrocyclic binuclear copper(II) complexes

Abstract

A series of binuclear copper(II) complexes of N-functionalized cyclam derivatives has been prepared by the Schiff base condensation of 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-l,4,8,11-tetraazacyclo-tetradecane (PC-a), 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-l,4,8,11-tetraazacyclo-tetradecane (PC-b) with appropriate aliphatic diamines, and copper(II) perchlorate. All the complexes were characterized by elemental, FT-IR, UV–Vis, ESI and ESR spectral analysis. The room temperature magnetic moment studies depicts the presence of an antiferromagnetic interaction in the binuclear complexes, which is also observed from the broad ESR spectra with a g value of 2.10–2.11. Variable-temperature magnetic susceptibility study of the complex [Cu2L2a](ClO4)2 shows that the calculated −2J value is 219 cm−1, which conveys a spin–spin interaction between the two copper(II) ions. The catechol oxidation and hydrolysis of 4-nitrophenylphosphate were carried out by using the complexes as a catalyst. All the above metal complexes were screened for antimicrobial and human pathogenic fungal activity. The binding of the complexes to calf thymus DNA (CT-DNA) has been investigated with UV–Vis and fluorescence spectroscopy. All complexes display significant cleavage property of circular plasmid pBR322 DNA into linear form. Spectral, electrochemical, magnetic and catalytic studies support the distortion of the copper ion geometry that arises as the macrocyclic ring size increases.