Akutagawa Tomoyuki, Sato Daisuke, Koshinaka Hiroyuki, Aonuma Masaaki, Noro Shin-ichiro, Takeda Sadamu, Nakamura Takayoshi
Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan.
Inorg Chem. 2008 Jul 7;47(13):5951-62. doi: 10.1021/ic800271m. Epub 2008 May 28.
Supramolecular rotators of hydrogen-bonding assemblies between anilinium (Ph-NH 3 (+)) or adamantylammonium (AD-NH 3 (+)) 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 (dmit (2-) is 2-thioxo-1,3-dithiole-4,5-dithiolate). The ammonium moieties of Ph-NH 3 (+) and AD-NH 3 (+) cations were interacted through N-H (+) approximately 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-NH 3 (+))(DB[18]crown-6)[Ni(dmit) 2] (-) ( 1) and (AD-NH 3 (+))(DB[18]crown-6)[Ni(dmit) 2] (-) ( 3), whereas the conformational flexibility of two dicyclohexyl rings was observed in (Ph-NH 3 (+))(DCH[18]crown-6)[Ni(dmit) 2] (-) ( 2) and (AD-NH 3 (+))(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 (1)H 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 (Delta E approximately 18 kJmol (-1)) and 4 (Delta E approximately 15 kJmol (-1)) were similar to those of ethane ( approximately 12 kJmol (-1)) and butane (17-25 kJmol (-1)) around the C-C single bond, which were 1 order of magnitude smaller than those of phenyl groups in salts 1 (Delta E approximately 180 kJmol (-1)) and 2 (Delta E approximately 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.
将苯胺鎓（Ph-NH₃⁺）或金刚烷铵（AD-NH₃⁺）与二苯并[18]冠-6（DB[18]冠-6）或内消旋二环己基[18]冠-6（DCH[18]冠-6）之间的氢键组装超分子转子引入[Ni(dmit)₂]盐中（dmit²⁻为2-硫代-1,3-二硫杂环戊烯-4,5-二硫醇盐）。Ph-NH₃⁺和AD-NH₃⁺阳离子的铵部分通过N-H⁺···O氢键与冠醚的六个氧原子相互作用，形成1:1超分子转子-定子结构。X射线晶体结构分析表明，在(Ph-NH₃⁺)(DB[18]冠-6)[Ni(dmit)₂]⁻（1）和(AD-NH₃⁺)(DB[18]冠-6)[Ni(dmit)₂]⁻（3）中，DB[18]冠-6呈折叠刀状构象，其中两个苯环沿同一方向扭曲，而在(Ph-NH₃⁺)(DCH[18]冠-6)[Ni(dmit)₂]⁻（2）和(AD-NH₃⁺)(DCH[18]冠-6)[Ni(dmit)₂]⁻（4）中观察到两个二环己基环的构象灵活性。在盐3和4的晶体中，金刚烷基团有足够的分子旋转空间，而盐1和2中苯基的旋转受到最近邻分子的相当限制。盐3和4中金刚烷基团的旋转通过温度依赖的宽线¹H NMR光谱、介电性质和X射线晶体结构分析得到证实。从头算计算表明，盐3（ΔE约为18 kJmol⁻¹）和盐4（ΔE约为15 kJmol⁻¹）中金刚烷基团旋转的势能垒与乙烷（约12 kJmol⁻¹）和丁烷（17 - 25 kJmol⁻¹）围绕C-C单键的势能垒相似，比盐1（ΔE约为180 kJmol⁻¹）和盐2（ΔE约为340 kJmol⁻¹）中苯基的势能垒小1个数量级。根据冠醚衍生物的形状，在晶体中观察到1D或2D [Ni(dmit)₂]⁻阴离子排列。盐1和3中[Ni(dmit)₂]⁻阴离子之间的2D弱分子间相互作用导致具有弱反铁磁相互作用的居里-外斯行为，而在盐2和4中观察到通过[Ni(dmit)₂]⁻阴离子之间横向硫-硫原子接触的1D相互作用，其磁行为分别由铁磁（盐2）和单重态-三重态（盐4）分子间磁相互作用决定。
