Structures of Ni(dmit)2 salts of lithium or ammonium included in crown ether assemblies

Tomoyuki Akutagawa, Takayoshi Nakamura, Tamotsu Inabe, Allan E. Underhill

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Three kinds of [Ni(dmit)2] (dmit = 2-thioxo-1,3-ditiol-4,5-dithiolate) salts containing 12-crown-4, 15-crown-5 or 18-crown-6 were prepared. In the crystal, the crown ethers form supramolecular assemblies in which counter cations are included. Lithium ions are located in the dimeric penta-coordinated ion cavity of [Li+]2[12-crown-4]3 unit of the [Li+]2[12-crown-4][Ni(dmit)2] 7[acetone]2 crystal. Each Li+ cation is coordinated by four oxygen atoms of a 12-crown-4 molecule and the oxygen of a second 12-crown-4 molecule which form a bridge to a further Li+ cation. Two 15-crown-5 molecules sandwich a NH+4 cation in the salt of [NH+4][15-crown-5]2[Ni(dmit)2]. The NH+4 ion is deca-coordinated by oxygen atoms of 15-crown-5 through weak hydrogen bonding. The cation-crown ether unit forms a dimer resulting in a barrel-like supramolecular cation. The [NH+4][18-crown-6][Ni(dmit)2]3 complex is composed of segregated trimer stacks of Ni(dmit)2 and isolated ion-captured cavities of [NH+4][18-crown-6]. The NH+4 ion is fully included in the cavity, and is tightly bounded through strong hydrogen bonds to the oxygen atoms of 18-crown-6, resulting in a disk-shaped supramolecular cation. The salts of [Li+]2[12-crown-4]3[Ni(dmit)2] 7[acetone]2 and [NH+4][18-crown-6][Ni(dmit)2]3 show semiconducting behaviour with the room-temperature conductivities of 30 and 0.4 S/cm, respectively, while [NH+4][15-crown-5]2[Ni(dmit)2] is insulating due to the mono-cation state of [Ni(dmit)2].

Original languageEnglish
Pages (from-to)264-271
Number of pages8
JournalThin Solid Films
Volume331
Issue number1-2
DOIs
Publication statusPublished - 1998
Externally publishedYes

Keywords

  • Crown ether
  • Crystal structure
  • Electrical conductivity
  • Ni(dmit) complex
  • Supramolecular cation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

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