Charge‐Transfer Solids Using Nucleobases: Supramolecular Architectures Composed of Cytosine and [Ni(dmit)2] Assembled by Multiple Hydrogen Bonds and Heteroatomic Contacts |
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| Authors: | Dr. Yukihiro Yoshida Dr. Mitsuhiko Maesato Dr. Manabu Ishikawa Dr. Yoshiaki Nakano Dr. Takaaki Hiramatsu Prof. Dr. Hideki Yamochi Prof. Dr. Gunzi Saito |
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| Affiliation: | 1. Faculty of Agriculture, Meijo University, Shiogamaguchi 1‐501 Tempaku‐ku, Nagoya 468‐8502 (Japan), Fax: (+81)?52‐833‐7200;2. Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo‐ku, Kyoto 606‐8502 (Japan);3. Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo‐ku, Kyoto 606‐8501 (Japan) |
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| Abstract: | Protonated species of the nucleobase cytosine (C), namely the monoprotonated CH+ and the hemiprotonated CHC+, were used to obtain four charge‐transfer complexes of [Ni(dmit)2] (dmit: 1,3‐dithiole‐2‐thione‐4,5‐dithiolate). Diffusion methods afforded two semiconducting [Ni(dmit)2]? salts; (CH)[Ni(dmit)2](CH3CN) ( 1 ) and (CHC)[Ni(dmit)2] ( 2 ). In salt 1 , the [Ni(dmit)2]? ions with a S=1/2 spin construct a uniform one‐dimensional array along the molecular long axis, and the significant intermolecular interaction along the face‐to‐face direction results in a spin‐singlet ground state. In contrast, salt 2 exhibits the Mott insulating behavior associated with uniform 1D arrays of [Ni(dmit)2]?, which assemble a two‐dimensional layer that is sandwiched between the layers of hydrogen‐bonded CHC+ ribbons. Multiple hydrogen bonds between CHC+ and [Ni(dmit)2]? seem to result in the absence of structural phase transition down to 0.5 K. Electrooxidation of [Ni(dmit)2]? afforded the polymorphs of the [Ni(dmit)2]0.5? salts, (CHC+)[{Ni(dmit)2}0.5?]2 ( 3 and 4 ), which are the first mixed‐valence salts of nucleobase cations with metal complex anions. Similar to 2 , salt 3 contains CHC+ ribbons that are sandwiched between the 2D [Ni(dmit)2]0.5? layers. In the layer, the [Ni(dmit)2]0.5? ions form dimers with a S=1/2 spin and the narrow electronic bandwidth causes a semiconducting behavior. In salt 4 , the CHC+ units form an unprecedented corrugated 2D sheet, which is sandwiched between the 2D [Ni(dmit)2]0.5? layers that involve ring‐over‐atom and spanning overlaps. In contrast to 3 , salt 4 exhibits metallic behavior down to 1.8 K, associated with a wide bandwidth and a 2D Fermi surface. The ability of hydrogen‐bonded CHC+ sheets as a template for the anion radical arrangements is demonstrated. |
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| Keywords: | conducting materials crystal engineering hydrogen bonds magnetic properties nucleobases |
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