Calcium ion (Ca2+) and crown ethers, 12-crown-4, 15-crown-5, 1-aza-18-crown-6 (A18-crown-6) and 1,10-diaza-18-crown-6 (DA18-crown-6), were assembled into divalent supramolecular cation (SC2+) structures in the monovalent [Ni(dmit)2]- salts (dmit2-=2-thioxo-1,3-dithiole-4,5-dithiolate), which regulate the arrangement of the [Ni(dmit)2]- anions in the crystal. The divalent SC2+-[Ni(dmit)2]- system showed a larger diversity of crystal structures compared with the monovalent SC+ system. Peculiar magnetic behavior was observed depending on the arrangement of the S=1/2 spins on the [Ni(dmit)2]- anions. Single crystals of Ca2+(12-crown-4)2[Ni(dmit)2]2 (1) and Ca2+ (15-crown-5)2[Ni(dmit)2]2(CH3CN) 0.7 (2) had a typical sandwich-type Ca2+ (crown ether)2 structure, which included the formation of π-π dimers and monomers of [Ni(dmit)2]- anions in the crystal. The temperature-dependent magnetic susceptibility (χm) of salt 1 showed a magnetic transition at 190 K, at which temperature the spins on each [Ni(dmit)2]- dimer formed a singlet pair. On the other hand, the magnetic behavior of salt 2 obeyed the Curie-Weiss law. The Ca2+ ions in the isostructural single crystals of Ca2+(A 18-crown-6)[Ni(dmit)2]2(CH3CN)2 (3) and Ca2+ (DA18-crown-6)[Ni(dmit)2]2(CH3CN) 2 (4) were completely included into the 18-crown-6 cavity, and further interacted with two CH3CN molecules from the axial position. The resultant Ca2+(18-crown-6)(CH3CN)2 cations induced the formation of uniform zig-zag chains of the [Ni(dmit)2]- anions, the magnetic susceptibility of which were explained by a one-dimensional Heisenberg antiferromagnetic linear chain. The magnetism of these salts was discussed in terms of the intermolecular transfer integral t.
ASJC Scopus subject areas
- Materials Chemistry