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

The 1D copper(II) complex {[Cu-2(L)(2)(fum)]center dot(H2O)center dot(MeOH)}(n) (1) has been synthesized using fumarate (fum(2-)) and a Schiff base (HL), derived from the condensation reaction of 2-amino-1-butanol and salicylaldehyde. Complex I has been characterized by its X-ray crystal structure, together with FT-IR, electronic absorption and fluorescence spectroscopic methods. The structural determination reveals that complex 1 crystallizes in the monoclinic system with the space group P2(1)/n and forms a 1D polymeric chain, built by bridging fum ligands. Weak pi center dot center dot center dot pi and C-H center dot center dot center dot pi interactions lead to the formation of a 3D supramolecular architecture. Complex 1 exhibits fluorescence (lambda(ex), 366 nm; lambda(em), 410, 433 and 462 nm) at room temperature, with a quantum yield (Phi(s)) 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 results show that the interaction of complex 1 with BSA/HSA occurs mainly with a ground state association process. The calculated values of the apparent association constants (at 300 K) are 1.34 x 10(4) and 1.81 x 10(4) L mol(-1) for interactions with BSA and HSA, respectively. The number of binding sites and binding constants were calculated using a double logarithm regression equation. The interaction of complex 1 with calf thymus DNA (CT-DNA) was also investigated using electronic absorption and fluorescence spectroscopic methods. The results show that complex 1 has a binding affinity to CT-DNA of the order of 2.96 x 10(5) L mol(-1). Low temperature magnetic measurements reveal the existence of an antiferromagnetic interaction in complex 1. The magnetic data have been fitted considering complex 1 as a pseudo-dinuclear system, with the two copper(II) ions 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) and g(Cu) = 2.20. (C) 2016 Elsevier Ltd. All rights reserved.