M+(12-crown-4) Supramolecular Cations (M+ = Na+, K+, Rb+, and NH4 +) within Ni(2-thioxo-1,3-dithiole-4,5-dithiolate)2 Molecular Conductor

• Published in: Inorganic chemistry 2000-06, Vol.39 (12), p.2645-2651
• Main Authors: Akutagawa, Tomoyuki, Hasegawa, Tatsuo, Nakamura, Takayoshi, Takeda, Sadamu, Inabe, Tamotsu, Sugiura, Ken-ichi, Sakata, Yoshiteru, Underhill, Allan E
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic000104a

Monovalent cations (M+ = Na+, K+, Rb+, and NH4 +) and 12-crown-4 were assembled to new supramolecular cation (SC+) structures of the M+(12-crown-4) n (n = 1 and 2), which were incorporated into the electrically conducting Ni(dmit)2 salts (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate). The Na+, K+, and Rb+ salts are isostructural with a stoichiometry of the M+(12-crown-4)2[Ni(dmit)2]4, while the NH4 + salt has a stoichiometry of NH4 +(12-crown-4)[Ni(dmit)2]3(CH3CN)2. The electrical conductivities of the Na+, K+, Rb+, and NH4 + salts at room temperature are 7.87, 4.46, 0.78, and 0.14 S cm-1, respectively, with a semiconducting temperature dependence. The SC+ structures of the Na+, K+, and Rb+ salts have an ion-capturing sandwich-type cavity of M+(12-crown-4)2, in which the M+ ion is coordinated by eight oxygen atoms of the two 12-crown-4 molecules. On the other hand, the NH4 + ion is coordinated by four oxygen atoms of the 12-crown-4 molecule. Judging from the M+−O distances, thermal parameters of oxygen atoms, and vibration spectra, the thermal fluctuation of the Na+(12-crown-4)2 structure is larger than those of K+(12-crown-4)2 and Rb+(12-crown-4)2. The SC+ unit with the larger alkali metal cation gave a stress to the Ni(dmit)2 column, and the SC+ structure changed the π−π overlap mode and electrically conducting behavior.