A supramolecular analog of cyclohexane sustained by aromatic C–H···π interactions between ferrocene moieties: molecular packing of ferrocene-containing thiosemicarbazato metal complexes

Abstract

Novel supramolecular cyclohexane-like structures, [NiL₂] (1) and [ZnL₂] (2) (HL=acetylferrocenyl thiosemicarbazone), have been constructed by self-assembly of ferrocene moieties ia aromatic C–H···π interactions. The nickel(II) atom in 1 is coordinated in a distorted square-planar cis configuration with two ferrocene-containing ligands positioned on the same side. One of the ferrocene moieties interacts with symmetry-related species to form a supramolecular arrangement that is topologically equivalent to cyclohexane, but in which edge-to-face C–H···π interactions between ferrocene moieties serve the same structural functions as the C–C bonds in cyclohexane. The zinc(II) atom in 2 is coordinated in a tetrahedral geometry with two equivalent Zn–S and Zn–N bonds. Each ferrocene moiety interacts with symmetry-related species using C–H···π interactions to form a two-dimensional cyclohexane-like network. Powder X-ray diffraction analyses of complexes 1 and 2, together with the palladium(II) complex [PdL₂] (3), copper(II) complex [CuL₂] (4), and cobalt(II) complex [CoL₂] (5) reveal that the supramolecular cyclohexane-like aggregation is robust enough to be exchanged from one network to another. All the results indicate that although C–H···π interactions have energies only in the 2–20 kJ mol⁻¹ range, these interactions are directional enough in combination that the orientation of molecules in the solid can be predicted with a reasonable degree of accuracy.