Copper(II) complexes of 1,3-dimethyl-5-(4′/3′-pyridylazo)-6-aminouracil: Structures, redox, magnetic and protein binding properties

Abstract

Two new monomeric copper(II) complexes based on 1,3-dimethyl-5-(4′/3′-pyridylazo)-6-aminouracil (HL1: 4′-pyridylazo, complex 1: cis-CuIIL12.MeOH; HL2: 3′-pyridylazo, complex 2: cis-CuIIL12.H2O) were synthesized, characterized and investigated for redox, magnetic and protein-binding properties. The complex 1 is in monoclinic space group C2/c, Z = 4 whereas the complex 2 is in triclinic space group P-1, Z = 2. The complexes hold similar structure in solid and solution state as could be infered from the EPR spectra of 1 having well-resolved hyperfine features, g|| > g┴ > ge (g|| =2.20 and g┴ =2.05). The E½ values for oxidative response of Cu(III)/Cu(II) couple are 1.030 V (ΔE = 133 mV) for 1 and 0.982 V (ΔE = 128 mV) for 2, indicating high redox stability of Cu(II) ions in the complex environment. Direct current (DC) variable-temperature magnetic susceptibility measurements on polycrystalline sample of 1 were carried out in the temperature range 1.8-300 K. The magnetic behavior indicates a weak antiferromagnetic interaction between Cu(II) ions in the crystal lattice below 25 K. The study of Bovin Serum Albumin (BSA)-complex interactions reveals that the BSA binds the complexes through the sites of tryptophan residues in 1:1 manner (n = 0.9007 & KA = 1.482 × 104M−1 for 1 and 0.7433 & KA =2.394×103M−1 for 2). Thus, the developed complexes could be treated as muti-functional materials.