An oxamato bridged trinuclear copper(II) complex: Synthesis, crystal structure, reactivity, DNA binding study and magnetic properties

A linear tri-nuclear oxamato bridged copper(II) complex [Cu-3(pba)(dpa)(2)(H2O)(ClO4)](ClO4)center dot H2O (1) (pbaH(4) = 1,3-propanediylbis(oxamic acid), dpa = 2,2'-dipyridylamine) was isolated from the reaction mixture of Na-2[Cu(pba)]center dot 3H(2)O, copper perchlorate hexahydrate and dipyridylamine in methanol. On reaction with dpa or DMF in basic medium (KOH) at ambient temperature complex 1 changed to dinuclear oxalate bridged copper(II) derivatives, [Cu-2(mu-C2O4)(dpa)(4)](ClO4)(2) (2) and [Cu-2(mu-C2O4)(dpa)(2) (DMF)(2)](ClO4)(2) (3), respectively. The complexes 1, 2 and 3 have been characterized by physicochemical and spectroscopic tools, and also by the X-ray single crystal analysis. The hydrolysis of 1 in basic medium and thermo-gravimetric analysis has been studied. Absorption and emission spectral studies showed that complex 1 interacts with calf thymus-DNA (CT-DNA) with a binding constant (K-b) of 4.01 x 10(4) M-1 and linear Stern-Volmer quenching constant (K-sv) of 6.9 x 10(4). A strong anti-ferromagnetic interaction with a coupling constant J(CuCu) of 320.0 +/- 0.3 cm(-1) was observed from the study of magnetic behavior of complex 1 in the temperature range of 2-300 K. Electrochemical equivalency of three copper(II) ions in 1 was identified by getting only one quasi reversible cyclic voltammogram. (C) 2011 Elsevier B. V. All rights reserved.