中间旋转S = 3/2单核Fe (III) 复合体中的缓慢磁放松
Xiaowen Feng1, Seung Jun Hwang1, Jun-Liang Liu2
1Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
Journal of the American Chemical Society
|October 26, 2017
概括
局部对称性显著影响铁 (III) 复合物的磁性异构性. 相对称的复合体表现出缓慢的磁放松和歇斯底里,与它们的扰动对应物不同.
科学领域:
- 无机化学
- 磁化学
- 材料科学
背景情况:
- 单核铁 (III) 复合物对于理解磁性属性至关重要.
- 局部对称性在确定过渡金属复合物的磁性行为中起着至关重要的作用.
- 研究磁体结构的相关性提供了关于磁性异构的见解.
研究的目的:
- 在两个单核铁 (III) 复合体中研究局部对称性对磁性异构的影响.
- 为了将结构对称性与磁性特性联系起来,
- 了解Fe (III) 系统中磁性行为的基本原理.
主要方法:
- 单核铁 (III) 复合物的合成和表征.
- 磁结构相关性研究.
- 磁性测量包括零场分裂 (ZFS) 参数的确定和慢磁放松分析.
主要成果:
- 复合物1具有较高的对称性,其ZFS参数 (D) 为 -50(2) cm−1,缓慢的磁放松和磁歇斯底里高达4K.
- 具有扰乱对称性的化合物2显示了减少的ZFS参数 (D) -17{\displaystyle \mathrm {D} } 1) cm−1和低能量屏障 (Ueff) 46 cm−1.
- 在研究的Fe (III) 复合体中显示出局部对称性和磁性异构性之间的明显关系.
结论:
- 局部对称性是控制单核铁 (III) 复合物的磁性异构的一个关键因素.
- 对称复合体可以显示增强的磁性特性,如缓慢放松和歇斯底里,这与分子磁性有关.
- 这些发现有助于单分子磁铁和磁性材料的合理设计.
相关概念视频
Atomic Nuclei: Types of Nuclear Relaxation
1.0K
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
1.0K
Atomic Nuclei: Nuclear Relaxation Processes
1.3K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
1.3K
Colors and Magnetism
14.2K
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...
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...
14.2K
Valence Bond Theory
11.4K
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...
11.4K
Atomic Nuclei: Nuclear Spin State Population Distribution
2.4K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
2.4K
Atomic Nuclei: Nuclear Spin State Overview
2.1K
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
2.1K

![Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59399.jpg&w=3840&q=50)
