Template synthesis, DNA binding, antimicrobial activity, Hirshfeld surface analysis, and 1D helical supramolecular structure of a novel binuclear copper(ii) Schiff base complex.

A new binuclear copper(ii) Schiff base complex [Cu L (NO)]·2CHOH (1) [ = 2,6-bis(()-(-tolylimino)methyl)-4-methoxyphenol] was synthesized using a template method in which the tridentate NO Schiff base ligand was derived from [1 + 2] condensation of 2,6-diformyl-4-methoxyphenol and -methyl aniline in the presence of copper(ii) ions as the template agent. The X-ray diffraction analyses revealed that this complex crystallizes in the monoclinic system with space group P2/. The most remarkable structural feature of 1 is that it contains two types of 1D right-handed helical chains. The molecules are linked by intermolecular hydrogen bonds and π⋯π interactions, then a 3D supramolecular network was constructed. Moreover, the intermolecular interactions on the crystal packing of 1 have been further studied using Hirshfeld surface analysis and corresponding 2D fingerprint plots. Binding interaction of this complex with calf thymus DNA (CT-DNA) has been investigated using absorption and emission studies, viscosity experiments and circular dichroism studies. Complex 1 shows significant binding to the DNA. The results of fluorescence spectroscopy and UV absorption spectroscopy, CD spectroscopy and viscosity indicated that this complex interacted with CT-DNA in a groove binding mode where the binding constant was 1.3 ± 0.2 × 10 L mol. Our fluorimeteric study showed that the reaction between 1 and CT-DNA was exothermic (Δ = 59.6 kJ mol; Δ = 268.79 J mol K). Antibacterial activities of the complex were screened by the disc diffusion method against three Gram-positive bacteria ( ATCC 25923, ATCC 23212 and ATCC 34384), and three Gram-negative bacteria ( ATCC 25922, ATCC 27853 and ATCC 70063). The results indicated that this complex demonstrated acceptable antibacterial activities.