Bis(μ-chloro) bridged 1D Cu^I and Cu^II coordination polymer complex and mononuclear Cu^II complex: Synthesis, crystal structure and biological properties

A novel one-dimensional coordination polymer containing –Cu(I)–Cu(II)– core with chloro bridge on Cu(I) and ligand bridge on Cu(II) ions (1) and a mononuclear Cu(II) complex (2) have been synthesized from the reactions of 3- and 4-methoxy-3-quinolin-3-ylimino-methyl-2-phenol with [CuCl₂(PPh₃)₂]. The ligands and the complexes have been characterized by spectral and analytical methods. In addition, the structures of both the ligands and the copper complexes were confirmed by single crystal X-ray diffraction studies. In both complexes, the phenolic oxygen and azomethine nitrogen atom of the ligand coordinate to the copper ions in a monobasic bidentate manner resulting in an approximately square planar geometry around the copper ion. In the polymeric complex, the N atom of the quinoline ring is coordinated to Cu(I) in addition to the phenolic oxygen and azomethine nitrogen atom coordinating to Cu(II) ion, thus bridging Cu(I) and Cu(II) ions in the complex. The interactions of the compounds with calf thymus DNA (CT-DNA) have been followed by absorption and emission titration methods, which revealed that the compounds interact with CT-DNA through intercalation. Further, the interactions of the compounds with bovine serum albumin (BSA) were also investigated using UV–visible, fluorescence spectroscopic methods. The results indicated that complex 1 exhibited a stronger binding to CT-DNA and BSA than the free ligands and complex 2. In addition, the in vitro cytotoxicity experiment showed that complexes 1 and 2 exhibit potent cytotoxic properties against PANC-1and Hela cells. Moreover, while complex 1 showed prominent cytotoxic activity against both PANC-1 and Hela cells with IC₅₀ of 17.91 and 11.67 μM, complex 2 showed moderate cytotoxic activities with IC₅₀ of 25.13 and 16.41 μM in PANC-1 and Hela cells. Further, apoptosis was confirmed by fluorescence image using EB/AO reagent.