Utilization of σ-Holes on Sulfur and Halogen Atoms for Supramolecular Cation···Anion Interactions in Bilayer Ni(dmit)2 Anion Radical Salts

Abstract

We prepared novel Ni(dmit)2 anion radical salts with ethyl-4-halothiazolium cations (Et-4XT, with X denoting the halogen: I, Br, or Cl), (Et-4IT)[Ni(dmit)2]2 (1), (Et-4BrT)[Ni(dmit)2]2 (2), and (Et-4ClT)2[Ni(dmit)2]5 (3). Single-crystal X-ray diffraction analysis of 1–3 indicates that, unlike the halogen atoms that have only one σ-hole each, the cations’ sulfur atoms each have two σ-holes that lie approximately along the extensions of the C–S bonds. The presence of the σ-holes is supported by electrostatic potential of the cations calculated based on the density functional theory method. In the crystals of 1–3, these σ-holes interact with lone pairs on the terminal thioketone moieties in the Ni(dmit)2 anion radicals to form electrostatic σ-hole bonds (halogen bonds and chalcogen bonds). This results in supramolecular cation···anion networks. Crystal and electronic structure analyses, and electrical and magnetic measurements reveal that the salts 1 and 2 are isostructural bilayer Mott systems, in which two...