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].
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