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

Abstract

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 19.6μg/mL. The antioxidant activities of the compounds were investigated with complex 1 showing higher activities against DPPH (150μM) and ABTS (160μm) 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.