ONO-pincer Zn(II) & Cd(II) complexes: Synthesis, structural characterization, Hirshfeld surface analysis and CT-DNA interactions

Abstract

Four new ONO pincer complexes of type Na2[Cd(L′)(OAc)2] (2a), Na2[Zn(L)(OAc)2] (3a), [Zn(LMe)(OAc)2] (4a) and [Cd(LMe)(OAc)2] (4b), where L′ = N,N'-bis(4-methylpyridin-2-yl)pyridine-2,6-dicarboximidate, L = N,N'-di(pyridin-2-yl)pyridine-2,6-dicarboximidate and LMe=N,N'-bis(1-methylpyridinium-2-yl)pyridine-2,6-dicarboximidate, were synthesized. The ligands were generated during complex formation reaction by the in situ deprotonation of their respective pro-ligands; H2L′ (2), H2L (3) and H2LMe (OTf)2 (4). The newly synthesized metal complexes were characterized by elemental analysis, FT-IR, NMR (1H and 13C), and single crystal X-ray diffraction techniques. The single crystal analysis of 4b disclosed that the central Cd(II) ion is adopting capped trigonal prism geometry. The nature of intermolecular interactions within the crystal structure, fingerprint plots, and molecular surface contours have been studied using Hirshfeld surface analysis. The DNA binding assay was conducted by molecular absorption spectroscopy, viscosity measurement and molecular modeling simulations. DNA-interaction measurements show that the compounds have a high propensity for binding with DNA as a groove binder.