固态连接体动力学在相互透的Mn[N(CN) ((2))) ((2)) ((pyrazine):一个中子光谱学研究
Craig M Brown1, Jamie L Manson
1Department of Materials and Nuclear Engineering, University of Maryland, College Park, Maryland 20742, USA.
Journal of the American Chemical Society
|October 17, 2002
概括
研究了相互透的协调聚合物的固态连接体动力学. 皮拉津配体的旋转动力学驱动着在410 K的可逆相变.
科学领域:
- 固态化学 固态化学
- 材料科学是一种材料科学.
- 中子散射是一种中子散射.
背景情况:
- 具有相互透的网格的协调聚合物具有独特的特性.
- 了解连接体动力学对于材料的功能至关重要.
- 在这样复杂的结构中,固态旋转动力学在很大程度上仍未被探索.
研究的目的:
- 为了研究双重透3D协调聚合物Mn[N(CN) 2) 2 ((pyz) 中的固态连接体动力学.
- 为了阐明在410K观察到的可逆结构相变的起源.
- 描述了pyrazine连接体的旋转运动及其温度依赖性.
主要方法:
- 准弹性中子散射 (QENS) 用于探测配体动力学.
- 差分扫描热量计 (DSC) 用于识别相位过渡.
- 高分辨率的回散光谱学提供了详细的运动分析.
主要成果:
- 在410K时确认了可逆结构相位过渡.
- 这种过渡是由桥梁氨酸 (pyz) 连接体的旋转动力学驱动的.
- 在425K,pyrazine环表现出180度的重定向跳跃 (τ ≈ 70 ps).
- 在200-410 K之间观察到纳秒时间尺度上的类似运动,激活能量为24 ± 2 kJ mol-1.
- 在2D分层变体 (β-Cu[N(CN) 2) 2 ((pyz)) 中没有检测到准弹性散射.
结论:
- 这项研究提供了第一次调查固态旋转动力学在一个相互透的格子结构.
- 皮拉津连接体的旋转动力学与观察到的相位过渡直接相关.
- 这些发现强调了格子结构在决定分子运动和相位行为的重要性.
更多相关视频
08:54Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
Published on: January 25, 2020
10:13A Technical Guide for Performing Spectroscopic Measurements on Metal-Organic Frameworks
Published on: April 28, 2023
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.
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
01:17Spin–Spin Coupling: One-Bond Coupling
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...