New organic conductors based on dibromo- and diiodo-TSeFs with magnetic and non-magnetic MX4 counter anions (M = Fe, Ga; X = Cl, Br)
New organic conductors based on dibromo- and diiodo-TSeFs with magnetic and non-magnetic MX4 counter anions (M = Fe, Ga; X = Cl, Br)
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DOI：
10.1039/b605420j
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发表时间：
2006-08
影响因子：
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通讯作者：
T. Shirahata;M. Kibune;M. Maesato;T. Kawashima;G. Saito;T. Imakubo
中科院分区：
文献类型：
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作者：
T. Shirahata;M. Kibune;M. Maesato;T. Kawashima;G. Saito;T. Imakubo
采用磁性和非磁性MX4反阴离子（M = Fe, Ga; X = Cl, Br）制备了八种卤化四硒戊烯（TSeF）衍生物二溴（乙烯二硫）四硒戊烯（DBrETSe）和二碘（乙烯二硫）四硒戊烯（DIETSe）阳离子基盐。DBrETSe盐的晶体结构取决于MX4反阴离子上的卤素种类。DBrETSe的MCl4盐是同构的，在正交空间群Ibam中结晶，而MBr4盐在单斜空间群C2/c中结晶。另一方面，DIETSe的4种MX4盐都是同构的，在正交空间群Ibam中结晶。在所有八种晶体中，供体分子形成所谓的β型分子排列，并观察到供体分子边缘的卤素原子与反阴离子之间的特征卤素键。（DBrETSe）2MX4 （M = Fe, Ga; X = Cl, Br）在4.2 K下表现出稳定的金属行为。这与它们的碘化类似物（DIETSe）2MCl4 （M = Fe, Ga）形成对比，后者在11 K时显示fel4盐的金属半导体转变，在12 K时显示GaCl4盐的金属半导体转变。含有非磁性阴离子的（DIETSe）2GaBr4没有观察到金属-半导体跃迁，但相应的含有磁性阴离子的FeBr4盐在7.2 K下观察到跃迁，这表明（DIETSe）2FeBr4的金属-半导体跃迁与π-d电子相互作用通过I⋯Br卤素键相关。在（DBrETSe）2FeX4和（DIETSe）2FeX4 （X = Cl, Br）中观察到FeX4阴离子d自旋的反铁磁有序。与FeCl4盐的低尼尔温度（TN≈2.5 K）相反，反铁磁有序发生在相对较高的温度下，即（DBrETSe）2FeBr4的TN = 7.5 K和（DIETSe）2FeBr4的TN = 7.0 K。由于（DBrETSe）2FeBr4的金属态保持在TN以下，该盐被归类为一种新型的反铁磁性有机金属。另一方面，（DIETSe）2FeBr4中d自旋的反铁磁有序与7k左右的金属-半导体跃迁协同发生。FeX4阴离子之间的d自旋的这些反铁磁顺序不能用直接的阴离子-阴离子相互作用来解释，因为它们在FeX4阴离子之间的卤素距离很长，并且强烈建议通过卤素键在供体和反阴离子之间进行π-d相互作用。
Eight cation radical salts based on halogenated tetraselenafulvalene (TSeF) derivatives, dibromo(ethylenedithio)tetraselenafulvalene (DBrETSe) and diiodo(ethylenedithio)tetraselenafulvalene (DIETSe), were prepared using magnetic and non-magnetic MX4 counter anions (M = Fe, Ga; X = Cl, Br). Crystal structures of the DBrETSe salts depend on the halogen species on the MX4 counter anion. The MCl4 salts of DBrETSe are isostructural and crystallize in the orthorhombic space group Ibam and those of the MBr4 salts crystallize in the monoclinic space group C2/c. On the other hand, all four MX4 salts of DIETSe are isostructural and crystallize in the orthorhombic space group Ibam. In all eight crystals, donor molecules form a so-called β-type molecular arrangement and characteristic halogen bonds between the halogen atoms on the edge of the donor molecules and those of the counter anions are observed. (DBrETSe)2MX4 (M = Fe, Ga; X = Cl, Br) show stable metallic behaviour down to 4.2 K. This is in contrast to their iodinated analogues (DIETSe)2MCl4 (M = Fe, Ga), which show a metal–semiconductor transition at 11 K for the FeCl4 salt and at 12 K for the GaCl4 salt. No metal–semiconductor transition is observed for (DIETSe)2GaBr4, which contains the non-magnetic anion, but the transition is observed at 7.2 K for the corresponding FeBr4 salt, which contains a magnetic anion, indicating that the metal–semiconductor transition of (DIETSe)2FeBr4 correlates to the π–d electronic interaction through the I⋯Br halogen bonds. Antiferromagnetic orderings of d spins of the FeX4 anions are observed in (DBrETSe)2FeX4 and (DIETSe)2FeX4 (X = Cl, Br). In contrast to the low Neel temperature (TN ≈ 2.5 K) of the FeCl4 salts, the antiferromagnetic orderings occur at relatively high temperatures, i.e.TN = 7.5 K for (DBrETSe)2FeBr4 and TN = 7.0 K for (DIETSe)2FeBr4. Since the metallic state of (DBrETSe)2FeBr4 remains below TN, this salt is classified as a novel antiferromagnetic organic metal. On the other hand, the antiferromagnetic ordering of the d spins in (DIETSe)2FeBr4 takes place cooperatively with the metal–semiconductor transition around 7 K. These antiferromagnetic orderings of the d spins between the FeX4 anions cannot be explained by direct anion–anion interactions because of their long halogen⋯halogen distances between the FeX4 anions, and the importance of the π–d interaction between the donors and the counter anions through the halogen bonds is strongly suggested.