Charge‐Transfer Solids Using Nucleobases: Supramolecular Architectures Composed of Cytosine and [Ni(dmit)2] Assembled by Multiple Hydrogen Bonds and Heteroatomic Contacts1. Issue 37 (29th July 2013)

• Record Type: Journal Article
• Authors: Yoshida, Yukihiro; Maesato, Mitsuhiko; Ishikawa, Manabu; Nakano, Yoshiaki; Hiramatsu, Takaaki; Yamochi, Hideki; Saito, Gunzi
• Is Part Of: Chemistry. Volume 19:Issue 37(2013)
• Page Start: 12325
• Page End: 12335
• Publication Date: 2013-07-29
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201300865
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Protonated species of the nucleobase cytosine (C), namely the monoprotonated CH<sup>+</sup> and the hemiprotonated CHC<sup>+</sup>, were used to obtain four charge‐transfer complexes of [Ni(dmit)<sub>2</sub>] (dmit: 1, 3‐dithiole‐2‐thione‐4, 5‐dithiolate). Diffusion methods afforded two semiconducting [Ni(dmit)<sub>2</sub>]<sup>−</sup> salts; (CH)[Ni(dmit)<sub>2</sub>](CH<sub>3</sub>CN) (<bold>1</bold>) and (CHC)[Ni(dmit)<sub>2</sub>] (<bold>2</bold>). In salt <bold>1</bold>, the [Ni(dmit)<sub>2</sub>]<sup>−</sup> ions with a <italic>S</italic>=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 <bold>2</bold> exhibits the Mott insulating behavior associated with uniform 1D arrays of [Ni(dmit)<sub>2</sub>]<sup>−</sup>, which assemble a two‐dimensional layer that is sandwiched between the layers of hydrogen‐bonded CHC<sup>+</sup> ribbons. Multiple hydrogen bonds between CHC<sup>+</sup> and [Ni(dmit)<sub>2</sub>]<sup>−</sup> seem to result in the absence of structural phase transition down to 0.5 K. Electrooxidation of [Ni(dmit)<sub>2</sub>]<sup>−</sup> afforded the polymorphs of the [Ni(dmit)<sub>2</sub>]<sup>0.5−</sup> salts, (CHC<sup>+</sup>)[{Ni(dmit)<sub>2</sub>}<sup>0.5−</sup>]<sub>2</sub> (<bold>3</bold> and <bold>4</bold>), which are the first mixed‐valence salts of nucleobase cations with metal complex anions. Similar to <bold>2</bold>, salt <bold>3</bold> contains CHC<sup>+</sup> ribbons that are sandwiched between the 2D [Ni(dmit)<sub>2</sub>]<sup>0.5−</sup> layers. In the layer, the [Ni(dmit)<sub>2</sub>]<sup>0.5−</sup> ions form dimers with a <italic>S</italic>=1/2 spin and the narrow electronic bandwidth causes a semiconducting behavior. In salt <bold>4</bold>, the CHC<sup>+</sup> units form an unprecedented corrugated 2D sheet, which is sandwiched between the 2D [Ni(dmit)<sub>2</sub>]<sup>0.5−</sup> layers that involve ring‐over‐atom and spanning overlaps. In contrast to <bold>3</bold>, salt <bold>4</bold> exhibits metallic behavior down to 1.8 K, associated with a wide bandwidth and a 2D Fermi surface. The ability of hydrogen‐bonded CHC<sup>+</sup> sheets as a template for the anion radical arrangements is demonstrated.</p> </abstract>