Molecular Conductors Based on the Mixed-Valence Polyoxometalates [SMo12O40]n− (n = 3 and 4) and the Organic Donors Bis(ethylenedithio)tetrathiafulv

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• 作者：Eugenio Coronado ; Simona Curreli ; Carlos Gimnez-Saiz ; Carlos J. Gmez-Garca ; Antonio Alberola ; Enric Canadell
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：December 7, 2009
• 年：2009
• 卷：48
• 期：23
• 页码：11314-11324
• 全文大小：1159K
• 年卷期：v.48,no.23(December 7, 2009)
• ISSN：1520-510X

文摘

The synthesis, crystal structure, and physical characterization of two new radical salts formed by the organic donors bis(ethylenedithio)tetrathiafulvalene (ET) and bis(ethylenediseleno)tetrathiafulvalene (BETS) and the Keggin polyoxometalate (POM) [SMo₁₂O₄₀]ⁿ⁻ are reported. The salts isolated are ET₈[SMo₁₂O₄₀]·10H₂O (1) (crystal data: (1) monoclinic, space group I2/m with a = 13.9300(10) Å, b = 43.467(3) Å, c = 13.9929(13) Å, β = 107.979(6)°, V = 8058.9(11) ų, Z = 2) and BETS₈[SMo₁₂O₄₀]·10H₂O (2) (crystal data: monoclinic, space group I2/m with a = 14.0878(2) Å, b = 44.1010(6) Å, c = 14.0930(2) Å, β = 106.739(3)°, V = 8384.8 ų, Z = 2). Both compounds are isostructural and consist of alternating layers of the organic donors (with an α or θ₄₂₊₄₀ packing mode) and POM anions. The structural data, as well as the magnetic susceptibility, ESR measurements, and band structure calculations, indicate that the Keggin POMs have been reduced by one electron in 1 and by two electrons in 2, leading to the POMs [SMo₁₂O₄₀]³⁻ and [SMo₁₂O₄₀]⁴⁻ in 1 and 2, respectively. At ambient pressure 1 is a classical semiconductor with a room temperature conductivity of about 1 S cm⁻¹ and an activation energy of about 130 meV. Salt 2 also exhibits an activated behavior although it does not follow a classical semiconducting regime. The conductivity of 2 under applied pressure shows an enhanced conductivity, in agreement with the analysis of the electronic structure, although no metallic behavior is detected below about 10 kbar.