A novel dinuclear double-stranded helical complexes of bis(terdentate) N4O2 donor ligand with silver(I) and zinc(II) d10 metal ions

Reaction of the hexadentate N4O2-donor ligand 6,6′-bis(3-hydrazonobutan-2-one)-2,2′-bipyridine (L) with Ag(I) and Zn(II) affords a dinuclear double stranded helicate species [Ag2L2]2+ (1a) and [Zn2L2]2+ (1b), in which partitioning of the ligand into two bis-tridentate pyridyl-ketoimine chelating units allow each ligand to bridge both metal centres. X-ray crystallography, ESI-MS and UV–Vis spectrophotometric titration experiments reveal that the complex (1a) retains its solid-state structure in solution. The crystal structure of (1a) provides the first example of dinuclear silver(I) complex in which both of the metal centres can be approximated as a seven coordinate distorted mono-capped trigonal prism in which the Ag⋯Ag close contact of 3.034(4) Å is taken into account and forms the cap. The counter-ions do not interact with metal centres but hydrogen bond to N–H protons of the hydrazonic arms from the separate strands. The adjacent helical units are cross-linked together via NH⋯Oketo hydrogen bonding to maintain the supramolecular structure.

A novel hexadentate N4O2 ligand 6,6′-bis(3-hydrazonobutan-2-one)-2,2′-bipyridine was shown to self-assembly into double-stranded helical complexes with d10 silver and zinc cations in solution; the corresponding [Ag2L2]2+ helicate (1a) shows a pseudo octahedral geometry about each silver(I) centre sharing a short Ag⋯Ag interaction to accomplish a seven-coordinate mono-capped trigonal prismatic arrangement.Figure optionsDownload as PowerPoint slide