DNA/protein binding and magnetic properties of a 1D Cu(II) complex containing fumarate and tridentate Schiff base ligands

Abstract

ID copper(II) complex, [Cu2(L)2(fum)]∙H2O}n (1) has been synthesized using fumarate (fum2-) and a Schiff base (HL), derived from the condensation reaction of 2-amino-1-butanol and salicyldehyde. Complex 1 has been characterized by X-ray crystal structure, FT-IR, electronic absorption and fluorescence spectroscopic methods. The structural determination reveals that complex 1 crystallizes in the monoclinic system with space group P21/n and form 1D polymeric chain, built by bridging fum. Weak π¿π and C-H¿π interactions in 1, lead to a 3D supramolecular architecture. Complex 1 exhibits fluorescence at room temperature with a quantum yield (Φs) of 0.257. The interactions of complex 1 with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic techniques and the analysis shows that complex 1 interaction with BSA / HSA occurs mainly with ground state association process. Calculated values of apparent association constants are 1.34 × 104 M-1 and 1.81 × 104 M-1 for BSA and HAS, respectively, at 300 K. The number of binding sites and binding constants were calculated using double logarithm regression equation. The interaction of complex 1 with the calf thymus DNA (CT-DNA) was also investigated using electronic absorption and fluorescence spectroscopic methods. The results show that complex 1 has binding affinity to CT-DNA in the order of 2.96×105 M-1. Low temperature magnetic measurements reveal existence of antiferromagnetic interaction in complex 1. The magnetic data have been fitted considering complex 1 as a pseudo-dinuclear system, with the two copper(II) atoms bridged by two carboxylate oxygen atoms, since the coupling through long fum bridge is almost nil. The best-fit parameters obtained with this model are J = - 60 cm-1, gCu = 2.20.