在正方形平面协调中高旋(II) 离子:氧硫化物Sr2CoO2Cu2S2和Ba2CoO2Cu2S2及其固体溶液的结构和磁性
Catherine F Smura1, Dinah R Parker, Mohamed Zbiri
1Department of Chemistry, University of Oxford, Oxford, UK.
Journal of the American Chemical Society
|February 10, 2011
概括
这项研究揭示了分层的氧甲基化物表现出反铁磁性排序,排序的磁矩随着Ba含量增加而增加,这是由于协调多面体的四角延长. 这种延长增强了(II) 离子中未灭的轨道成分.
科学领域:
- 材料科学 材料科学 材料科学
- 固态物理 固态物理
- 无机化学 无机化学 有机化学
背景情况:
- 层层的氧基化物 (Sr(1-x) Ba(x)) ((2) CoO(2) Cu(2) S(2) 被研究它们的磁性特性.
- 这些化合物中的 (II) 离子由氧化物和硫化物协调,形成四边长的八面体.
研究的目的:
- 使用粉末中子衍射确定 (Sr(1-x) Ba(x)) ((2) CoO(2) Cu(2) S(2) 的反铁磁结构.
- 调查结构参数,特别是四边形延长和 (II) 离子的磁性特性之间的相关性.
主要方法:
- 粉末中子衍射被用来确定晶体和磁性结构.
- 进行了ab initio计算以支持实验观测.
主要成果:
- 观察到反铁磁的顺序,与最近的邻居 (二) 时刻在CoO (二) 平面内反铁磁合.
- 的有序磁矩 (II) 随着含量增加而增加,与CoO的四边长延伸有关.
- 由于暴露在潮湿的空气中,导致铜缺乏导致有序磁矩的减少.
结论:
- 协调环境的四角延长显著影响了磁性,特别是未灭的轨道组成部分.
- 观察到的低于尼尔温度的磁力阻力扭曲与有序磁矩的大小有关.
相关概念视频
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:34Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
02:42Ionic Crystal Structures
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
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Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...