Novel ruthenium(II) and (III) compounds with multidentate Schiff base chelates bearing biologically significant moieties

In this account, we report the isolation of novel ruthenium(II/III) compounds from the respective reactions of the metal precursor, trans-[RuCl2(PPh3)3] with multidentate Schiff base ligands bearing biologically significant moieties (viz. antipyrine, uracil or chromone). From these coordination reactions of trans-[RuCl2(PPh3)3] with 4-((pyridine-2yl)methyleneimino)antipyrine (pap), 4-((pyridine-2-ylimino)methylene)-chromone (pch), 2,6-bis-((6-amino-1,3-dimethyluracilimino)methylene)pyridine (H4ucp) and 2,6-bis-((antipyrine-imino)methylene)pyridine (bpap); the complex salt, trans-[RuIICl(pap)(PPh3)2]BF4 and the ruthenium(II/III) complexes: trans-P, cis-Cl-[RuIII(pch)Cl2(PPh3)2], [RuII(H3ucp)Cl(PPh3)] and cis-[RuIICl2(bpap)(PPh3)] were formed, respectively. These ruthenium compounds were characterized via multinuclear NMR, IR, UV–Vis, emission and ESR spectroscopy, conductivity measurements as well as structural elucidations were confirmed via single crystal X-ray diffraction. The redox properties of metallic compounds were investigated by voltammetric analysis. In addition, DFT studies of [RuII(H3ucp)Cl(PPh3)] were conducted to provide insight into its intrinsic solid state structural features.

The diimine ruthenium complexes, [RuII(H3ucp)Cl(PPh3)] (3) and cis-[RuIICl2(bpap)(PPh3)] (4) were isolated from the equimolar coordination reactions of trans-[RuCl2(PPh3)3] with 2,6-bis-((6-amino-1,3-dimethyluracilimino)methylene)pyridine (H4ucp) and 2,6-bis-((antipyrine-imino)methylene)pyridine (bpap), respectively. The distinctive difference in the structural features of the diimine and mono-imine ruthenium compounds are also reflected in their redox behaviors.Figure optionsDownload as PowerPoint slide