Synthesis, crystal structure, DNA-binding and cytotoxicity in vitro of novel cis-Pt(II) and trans-Pd(II) pyridine carboxamide complexes

In an attempt to establish fundamental structure–activity relationships (SAR) of Pt/Pd-based anti-tumour compounds, we have recently designed monodentate pyridyl amide ligand containing central amide units which possess external metal co-ordinating pyridyl group and internal amide functionality. It was prepared in one step from commercially available compounds in moderate to good yield. Surprisingly, treatment of K2[MCl4] [M = Pt(II), Pd(II)] with ligand N-(4-chlorophenyl)-3-pyridinecarboxamide (L) in the same reaction condition affords two different hydrogen-bonded polymers: cis-[PtL2Cl2]·CH3OH·DMF (1) and trans-[PdL2Cl2]·2DMF (2). Fluorescence analysis indicates that the two complexes can bind to fish sperm DNA (FS-DNA) and gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR322 plasmid DNA. The two complexes exhibit cytotoxic specificity and significant cancer cell inhibitory rate. Furthermore, cytotoxicity values are higher in the case of cis-Pt(II) complex than trans-Pd(II) complex in four different cancer cell lines.

Graphical abstractThe synthesis, crystal structure, interaction with DNA and cytotoxic activity of two cis-platinum and trans-palladium complexes, (1) cis-[PtL2Cl2]·CH3OH·DMF and (2) trans-[PdL2Cl2]·2DMF (where L = N-(4-chlorophenyl)-3-pyridinecarboxamide), are described. We have probed that the effect of solvent molecule on the network structure and activity of the resulting self-assembled products.Figure optionsDownload full-size imageDownload as PowerPoint slide