The Series of Molecular Conductors and Superconductors ET4[AFe(C2O4)3]路PhX (ET = bis(ethylenedithio)tetrathiafulvalene; (C2O4)2鈥?

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• 作者：Eugenio Coronado ; Simona Curreli ; Carlos Gim茅nez-Saiz ; Carlos J. G贸mez-Garc铆a
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：January 16, 2012
• 年：2012
• 卷：51
• 期：2
• 页码：1111-1126
• 全文大小：660K
• 年卷期：v.51,no.2(January 16, 2012)
• ISSN：1520-510X

文摘

An extensive series of radical salts formed by the organic donor bis(ethylenedithio)tetrathiafulvalene (ET), the paramagnetic tris(oxalato)ferrate(III) anion [Fe(C₂O₄)₃]^{3鈥?/sup>, and halobenzene guest molecules has been synthesized and characterized. The change of the halogen atom in this series has allowed the study of the effect of the size and charge polarization on the crystal structures and physical properties while keeping the geometry of the guest molecule. The general formula of the salts is ET₄[AIFe(C₂O₄)₃]路G with A/G = H₃O+/PhF (1); H₃O+/PhCl (2); H₃O+/PhBr (3), and K+/PhI (4), (crystal data at room temperature: (1) monoclinic, space group C2/c with a = 10.3123(2) 脜, b = 20.0205(3) 脜, c = 35.2732(4) 脜, 尾 = 92.511(2)掳, V = 7275.4(2) 脜3, Z = 4; (2) monoclinic, space group C2/c with a = 10.2899(4) 脜, b = 20.026(10) 脜, c = 35.411(10) 脜, 尾 = 92.974掳, V = 7287(4) 脜3, Z = 4; (3) monoclinic, space group C2/c with a = 10.2875(3) 脜, b = 20.0546(15) 脜, c = 35.513(2) 脜, 尾 = 93.238(5)掳, V = 7315.0(7) 脜3, Z = 4; (4) monoclinic, space group C2/c with a = 10.2260(2) 脜, b = 19.9234(2) 脜, c = 35.9064(6) 脜, 尾 = 93.3664(6)掳, V = 7302.83(18) 脜3, Z = 4). The crystal structures at 120 K evidence that compounds 1鈥?b>3 undergo a structural transition to a lower symmetry phase when the temperature is lowered (crystal data at 120 K: (1) triclinic, space group P1̅ with a = 10.2595(3) 脜, b = 11.1403(3) 脜, c = 34.9516(9) 脜, 伪 = 89.149(2)掳, 尾 = 86.762(2)掳, 纬 = 62.578(3)掳, V = 3539.96(19) 脜3, Z = 2; (2) triclinic, space group P1̅ with a = 10.25276(14) 脜, b = 11.15081(13) 脜, c = 35.1363(5) 脜, 伪 = 89.0829(10)掳, 尾 = 86.5203(11)掳, 纬 = 62.6678(13)掳, V = 3561.65(8) 脜3, Z = 2; (3) triclinic, space group P1̅ with a = 10.25554(17) 脜, b = 11.16966(18) 脜, c = 35.1997(5) 脜, 伪 = 62.7251(16)掳, 尾 = 86.3083(12)掳, 纬 = 62.7251(16)掳, V = 3575.99(10) 脜3, Z = 2; (4) monoclinic, space group C2/c with a = 10.1637(3) 脜, b = 19.7251(6) 脜, c = 35.6405(11) 脜, 尾 = 93.895(3)掳, V = 7128.7(4) 脜3, Z = 4). A detailed crystallographic study shows a change in the symmetry of the crystal for compound 3 at about 200 K. This structural transition arises from the partial ordering of some ethylene groups in the ET molecules and involves a slight movement of the halobenzene guest molecules (which occupy hexagonal cavities in the anionic layers) toward one of the adjacent organic layers, giving rise to two nonequivalent organic layers at 120 K (compared to only one at room temperature). The structural transition at about 200 K is also observed in the electrical properties of 1鈥?b>3 and in the magnetic properties of 1. The direct current (dc) conductivity shows metallic behavior in salts 1鈥?b>3 with superconducting transitions at about 4.0 and 1.0 K in salts 3 and 1, respectively. Salt 4 shows a semiconductor behavior in the temperature range 300鈥?0 K with an activation energy of 64 meV. The magnetic measurements confirm the presence of high spin S = 5/2 [Fe(C₂O₄)₃]3鈥?/sup> isolated monomers together with a Pauli paramagnetism, typical of metals, in compounds 1鈥?b>3. The magnetic properties can be very well reproduced in the whole temperature range with a simple model of isolated S = 5/2 ions with a zero field splitting plus a temperature independent paramagnetism (N伪) with the following parameters: g = 1.965, |D| = 0.31 cm鈥?, and N伪 = 1.5 脳 10鈥? emu mol鈥? for 1, g = 2.024, |D| = 0.65 cm鈥?, and N伪 = 1.4 脳 10鈥? emu mol鈥? for 2, and g = 2.001, |D| = 0.52 cm鈥?, and N伪 = 1.5 脳 10鈥? emu mol鈥? for 3.}