Solid-state molecular rotators of anilinium and adamantylammonium in [Ni(dmit)2]- salts with diverse magnetic properties

Tomoyuki Akutagawa, Daisuke Sato, Hiroyuki Koshinaka, Masaaki Aonuma, Shin Ichiro Noro, Sadamu Takeda, Takayoshi Nakamura

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Supramolecular rotators of hydrogen-bonding assemblies between anilinium (Ph-NH3+) or adamantylammonium (AD-NH3 +) and dibenzo[18]crown-6 (DB[18]crown-6) or meso-dicyclohexano[18] crown-6 (DCH[18]crown-6) were introduced into [Ni(dmit)2] salts (dmit2- is 2-thioxo-1,3-dithiole-4,5-dithiolate). The ammonium moieties of Ph-NH3+ and AD-NH3+ cations were interacted through N-H+∼O hydrogen bonding with the six oxygen atoms of crown ethers, forming 1:1 supramolecular rotator-stator structures. X-ray crystal-structure analyses revealed a jackknife-shaped conformation of DB[18]crown-6, in which two benzene rings were twisted along the same direction, in (Ph-NH3+)(DB[18]crown-6)[Ni(dmit) 2]- (1) and (AD-NH3+)(DB[18]crown-6) [Ni(dmit)2]- (3), whereas the conformational flexibility of two dicyclohexyl rings was observed in (Ph-NH3+)(DCH[18]crown-6) [Ni(dmit)2]- (2) and (AD-NH3 +)(DCH[18]crown-6)[Ni(dmit)2]_ (4). Sufficient space for the molecular rotation of the adamantyl group was achieved in the crystals of salts 3 and 4, whereas the rotation of the phenyl group in salts 1 and 2 was rather restricted by the nearest neighboring molecules. The rotation of the adamantyl group in salts 3 and 4 was evidenced from the temperature-dependent wide-line 1H NMR spectra, dielectric properties, and X-ray crystal structure analysis, ab initio calculations showed that the potential energy barriers for the rotations of adamantyl groups in salts 3 (ΔE ≈ 18 kJmol-1) and 4 (ΔE ≈ 15 kJmol -1) were similar to those of ethane (∼12 kJmol-1) and butane (17-25 kuJmol-1) around the C-C single bond, which were 1 order of magnitude smaller than those of phenyl groups in salts 1 (ΔE ≈ 180 kJmol-1) and 2 (ΔE ≈ 340 kJmol-1). 1D or 2D [Ni(dmit)2]- anion arrangements were observed in the crystals according to the shape of crown ether derivatives. The 2D weak intermolecular interactions between [Ni(dmit)2]- anions in salts 1 and 3 led to Curie-Weiss behavior with weak antiferromagnetic interaction, whereas 1D interactions through lateral sulfur-sulfur atomic contacts between [Ni(dmit)2]- anions were observed in salts 2 and 4, whose magnetic behaviors were dictated by ferromagnetic (salt 2) and singlet-triplet (salt 4) intermolecular magnetic interactions, respectively.

Original languageEnglish
Pages (from-to)5951-5962
Number of pages12
JournalInorganic Chemistry
Issue number13
Publication statusPublished - 2008 Jul 7


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