Becker Richard, Johnsson Mats, Kremer Reinhard K, Klauss Hans-Henning, Lemmens Peter
Department of Inorganic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden.
J Am Chem Soc. 2006 Dec 6;128(48):15469-75. doi: 10.1021/ja064738d.
A new layered transition metal oxohalide, FeTe2O5ClxBr1-x, has been identified. It crystallizes in the monoclinic space group P21/c. The unit cell for FeTe2O5Br is a = 13.3964(8), b = 6.5966(4), c = 14.2897(6) A, beta=108.118(6) degrees, and Z=8. The layers are built of edge sharing [FeO6] octahedra forming [Fe4O16]20- units that are linked by [Te4O10X2]6- groups. The layers have no net charge and are only weakly connected via van der Waals forces to adjacent layers. There are four crystallographically different Te atoms, and one of them displays a unique [TeO2X] coordination polyhedron (X=Cl, Br). Magnetic susceptibility measurements show a broad maximum typical for 4-spin clusters of coupled Fe(III) ions in the high-spin state. Evidence for magnetic instabilities exists at low temperatures, which have been confirmed with specific heat experiments. A theoretical modeling of the susceptibility concludes a frustration of the intra-tetramer anti-ferromagnetic exchange interaction.
一种新型层状过渡金属氧卤化物FeTe2O5ClxBr1-x已被发现。它结晶于单斜空间群P21/c。FeTe2O5Br的晶胞参数为a = 13.3964(8)，b = 6.5966(4)，c = 14.2897(6) Å，β = 108.118(6)°，Z = 8。这些层由边共享的[FeO6]八面体构成，形成[Fe4O16]20-单元，这些单元通过[Te4O10X2]6-基团相连。这些层没有净电荷，仅通过范德华力与相邻层微弱相连。存在四个晶体学上不同的Te原子，其中一个呈现独特的[TeO2X]配位多面体（X = Cl，Br）。磁化率测量显示出高自旋态下耦合Fe(III)离子的4自旋簇典型的宽峰。在低温下存在磁不稳定性的证据，并已通过比热实验得到证实。磁化率的理论建模得出四聚体内反铁磁交换相互作用受挫的结论。
