Sandwich-type supramolecular cation structures of (M+)( crown-4)2 complexes (M+ = Li+, Na+, K+, and Rb+) were introduced as countercations to the [Ni(dmit)2]- anion, which bears an S = 1/2 spin, to form novel magnetic crystals (dmit2- = 2-thione-1,3-dithiole-4,5- dithiolate). The zigzag arrangement of Li+(crown-4)2 cations in Li+(crown-4)2[Ni(dmit)2] - salt induced weak intermolecular interactions of [Ni(dmit) 2]- dimers, whose magnetic spins were isolated from each other. The molecular arrangements of cations and anions in M+( crown-4)2[Ni(dmit)2]- salts (M+ = Na+, K+, and Rb+) were isostructural to each other. In the case of Na+(crown-4)2[Ni(dmit) 2]-, the space group C2/m changed to C2/c with a lowering in temperature from 298 to 100 K. This structural change occurred at 222.5 K as a first-order phase transition. The space group C2/m (T = 298 K) in the salt K+(crown-4)2[Ni(dmit)2]- also changed to C2/c (T = 100 K), which transition occurred at 270 K. Crystal structural analyses at 298 and 100 K revealed changes in both supramolecular cation conformation and [Ni(dmit)2]- anion arrangements. The transition from C2/m to C2/c crystals generated a dipole moment in the Na+(crown-4)2 and K+(crown-4) 2 structures, which were reconstructed to cancel the net dipole moment of the C2/c crystals. These cation transformations led to changes in intermolecular interactions between the [Ni(dmit)2]- anions via structural rearrangements. The crystal structure of C2/c was stabilized in Rb+(crown-4)2[Ni(dmit)2] - at 298 K. The [Ni(dmit)2]- configuration in these salts with the C2/c space group was a one-dimensional uniform chain, which showed the temperature-dependent magnetic susceptibility of a one-dimensional linear Heisenberg antiferromagnetic chain.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry