Coordination behaviour of bis-terdentate N-donor ligands: Double- and single-stranded helicates, mesocates, and cyclic oligomers

Nawal K. Al-Rasbi, Harry Adams, Lindsay P. Harding, Michael D. Ward

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Three new ligands have been prepared in which two terdentate chelating pyrazolyl-bipyridine units are connected by a central aromatic spacer via methylene "hinges": the spacers are o-phenylene (LPh), 2,6-pyridine-diyl (LPy) and 2,3-naphthalenediyl (Lnaph). The ligands act as potentially hexadentate bridging ligands, with the central pyridyl N atom of LPy not involved in coordination. The following complexes were prepared and structurally characterised: [M2(L Ph)2][ClO4]4 (M = Ni, Cu), which are dinuclear double helicates; [Ag2-(LPh)(MeCN) 2][BF4]2, a dinuclear complex with an Ag⋯Ag bond in which the ligand adopts a helical twist around the pair of metal ions; [Ni2(LPy)2][BF4] 4, an achiral "mesocate" with a box-like structure and a face-to-face arrangement of ligands; [Ag3(Lnaph) 2](BF4)3, which contains a linear trinuclear array of AgI ions with the two ligands arranged in a shallow helical twist, each ligand spanning one terminal and the central metal ion; and [Cd 6(Lnaph)6](ClO4)12, a cyclic hexanuclear helicate with a perchlorate anion in the central cavity. Both [Cu2(LPh)2][ClO4]4 and [Cd6(Lnaph)6](ClO4)12, which have architecturally similar bridging ligands, show evidence by electrospray mass spectrometry for formation of a range of cyclic oligomers in solution up to 11-mers for the CdII/Lnaph system.

Original languageEnglish
Pages (from-to)4770-4780
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Issue number30
Publication statusPublished - 2007



  • Chelating ligands
  • Coordination chemistry
  • Helical structures
  • Self-assembly

ASJC Scopus subject areas

  • Inorganic Chemistry

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