Conducting dimerized cobalt complexes with tetrathiafulvalene dithiolate ligands

Emiko Fujiwara, Kazumasa Hosoya, Akiko Kobayashi, Hisashi Tanaka, Madoka Tokumoto, Yoshinori Okano, Hideki Fujiwara, Hayao Kobayashi, Yuichi Fujishiro, Eiji Nishibori, Masaki Takata, Makoto Sakata

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15 Citations (Scopus)


To obtain novel single-component molecular metals, we attempted to synthesize several cobalt complexes coordinated by TTF (tetrathiafulvalene)-type dithiolate ligands. We succeeded in the syntheses and structure determinations of (nBu4N)2[Co(chdt)2]2 (1), (nBu4N)2[Co(dmdt)2]2 (2), [Co(dmdt)2]2 (3), and [Co(dt)2] 2 (4) (chdt = cyclohexeno-TTF-dithiolate, dmdt = dimethyl-TTF- dithiolate, and dt = TTF-dithiolate). Structure analyses of complexes 1-4 revealed that two monomeric [Co(ligand)2]- or [Co(ligand)2]0 units are connected by two Co-S bonds resulting in dimeric [Co(ligand)2]22- or [Co(ligand)2]2 molecules. Complex 1 has a cation-anion-intermingled structure and exhibited Curie-Weiss magnetic behavior with a large Curie constant (C - 2.02 K·emu·mol-1) and weak antiferromagnetic interactions (θ = -8.3 K). Complex 2 also has a cation-anion-intermingled structure. However, the dimeric molecules are completely isolated by cations. Complexes 3 and 4 are single-component molecular crystals. The molecules of complex 3 form two-dimensional molecular stacking layers and exhibit a room-temperature conductivity of σrt = 1.2 × 10-2 S·cm-1 and an activation energy of Ea = 85 meV. The magnetic behavior is almost consistent with Curie-Weiss law, where the Curie constant and Weiss temperature are 8.7 × 10-2 K·emu·mol-1 and -0.85 K, respectively. Complex 4 has a rare chair form of the dimeric structure. The electrical conductivity was fairly large (σrt = 19 S·cm -1), and its temperature dependence was very small (σ0.55Krt = ca. 1:10), although the measurements were performed on the compressed pellet sample. Complex 4 showed an almost constant paramagnetic susceptibility (χ300 K = 3.5 × 10-4 emu·mol-1) from 300 to 50 K. The band structure calculation of complex 4 suggested the metallic nature of the system. Complex 4 is a novel single-component molecular conductor with a dimeric molecular structure and essentially metallic properties down to very low temperatures.

Original languageEnglish
Pages (from-to)863-874
Number of pages12
JournalInorganic Chemistry
Issue number3
Publication statusPublished - 2008 Feb 4


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