Crystal structures of o,o′-(N,N′-dipicolinyldene)diazadiphenyl disulfide and its copper (II) complex: Antioxidant, antibacterial and DNA-binding properties

•Synthesis and characterization of o,o′-(N,N′-dipicolinyldene)diazadiphenyl disulfide and its copper complex.•S–S bond is cleaved prior to coordination with copper.•Investigation and comparison of antibacterial, antioxidant and DNA binding of ligand and its copper complex.

Copper (II) complex [Cu(L)Cl] (1) was synthesized by the reaction of o,o′-(N,N′-dipicolinyldene)diazadiphenyl disulfide (L–L) with copper (II) chloride. L–L and 1 were structurally characterized by spectral and single X-ray crystallography. X-ray structure of 1 showed that the copper atom is found in a square planar geometry and is bonded to azomethine nitrogen, sulfur, nitrogen of pyridine and chloride atoms. The compounds were examined for their antibacterial, antioxidant, DNA-binding activities. Complex 1 was found to display higher antibacterial activities compared to L–L, being more active against Klebsiella pneumonia with a MIC of 19.6 μg/mL. The antioxidant activities of the compounds were investigated with complex 1 showing higher activities against DPPH (150 μM) and ABTS (160 μm) radicals. The DNA-binding properties of L–L and 1 have been investigated by electronic absorption, fluorescence and viscosity measurements. They were found bind to DNA via groove binding mode with an intrinsic binding constant, Kb of 1 × 107 (L–L) and 6.5 × 103 M−1 (1), respectively. L–L and complex 1 were found to cleave DNA effectively via singlet oxygen oxidative pathway. This study reveals the possible use of L–L and its copper complex in pharmaceutical application.

Graphical abstractThe crystal structures of o,o′-(N,N′-dipicolinyldene)diazadiphenyl disulfide (L–L) and its copper complex are reported. The S–S bond in L–L was found to cleave prior to coordination. Both compounds show significant antioxidant, antibacterial and DNA binding activities.Figure optionsDownload full-size imageDownload as PowerPoint slide