Structural evidence for the facile chelate-ring opening reactions of novel platinum(ii)–pyridine carboxamide complexes

Abstract

The design of Pt(II) complexes with novel structural features is of great relevance in the search for new anticancer agents with innovative chemical and biological properties. In this work we have synthesised and structurally characterised three novel Pt(II) complexes with a pyridine carboxamide ligand (HL). The X-ray structural analysis shows that complex 1, [Pt(L-N, N')₂] crystallises in space group C2, while complex 2, [Pt(L-N,N')(L-N)Cl] crystallises in space group P2₁. ESMS and ¹H NMR data show that one of the two ligands in complex 1 undergoes a fast ring-opening reaction to give complex 2 in the presence of Cl⁻. Complex 2 demonstrated notable activity against human and murine leukemia cells (HL-60 and P388), but rather weak potency against lung adenocarcinoma A-549. However, complex 1 was found to be basically inactive against the above cell lines. This work provides new examples in the design of platinum compounds that can be activated in vivo by biological anions.