Synthesis, DNA-binding and cleavage studies of macrocyclic copper(II) complexes

Abstract

Two macrocyclic copper(II) complexes, [CuL1](ClO4)2 (L1 = 2,6,9,13-tetraparacyclophane, a Schiff base) and [CuL2]Cl2 [L2 = 3,10-bis(2-benzyl)-1,3,5,8,10,13-hexaazacyclotetradecane] have been prepared and characterized by elemental analysis, u.v.–vis., i.r. and mass spectra. Absorption, fluorescence, circular dichroic spectra and viscosity experiments have been carried out on the interaction of the two complexes with calf thymus CT DNA. The results suggest that both complexes can bind to CT DNA by intercalation via the aromatic moiety ring in the macrocycle into the base pairs of DNA. [CuL1](ClO4)2 binds to CT DNA more strongly than [CuL2]Cl2. The position of the aromatic ring in the macrocycle plays an important role in deciding the extent of binding of the complexes to DNA. Significantly, the complexes have been found to be single-strand DNA cleavers in the presence of H2O2 or/and 2-mercaptoethanol.