2-Benzoylpyridine and copper(II) ion in basic medium: Hydroxide nucleophilic addition stabilized by metal complexation, reactivity, crystal structure, DNA binding study and magnetic behavior

On reaction of 2-benzoylpyridine (Bzpy) with copper(II) ion, different types of copper(II) complexes have been isolated in pure form depending upon the counter anion of the copper(II) salts used as reactant and the pH of the medium. Mono-nuclear copper(II) complexes of formula [Cu(Bzpy)2(ClO4)2] (1) and [Cu(Bzpy)2(H2O)2](NO3)2 (2) were formed with copper(II) perchlorate and nitrate, respectively. On the other hand, following a similar reaction type in presence of alkali, we obtained the dinuclear copper(II) complex [Cu2(Bzpy)2{BzOpy}2(H2O)](ClO4)2 (3) containing the hydroxy-2-pyridylphenylmethanolato (BzOpy)− anion, achieved through the nucleophilic addition of the hydroxide to the carbonyl group of Bzpy, which is stabilized by metal complexation. However, this behavior was not recorded with copper(II) nitrate. The complexes were characterized by physicochemical and spectroscopic tools along with structural characterization by single crystal X-ray diffraction analysis. The interaction of dinuclear copper(II) complex 3 with calf thymus DNA (CT-DNA) has been investigated by using absorption and emission spectral studies and the binding constant (Kb) and the linear Stern–Volmer quenching constant (Ksv) have been determined. Complex 3 was active to oxidize the catechol to the corresponding quinone in MeCN medium via complex-catechol intermediate. Magnetic behavior for 3 is typical for uncorrelated spins down even up to 2 K.