复合物的2H固态核磁共振
Bernadeta Walaszek1, Anna Adamczyk, Tal Pery
1Institut für Physikalische and Theoretische Chemie, Freie Universität Berlin, Takustr.3, D-14195 Berlin, Germany.
Journal of the American Chemical Society
|December 5, 2008
概括
这项研究使用NMR分析过渡金属复合体作为纳米粒子表面模型. 四极合常量有助于描述这些表面上的不同物种.
科学领域:
- 固态核磁共振 (NMR) 光谱学 固态核磁共振 (NMR) 光谱学
- 材料科学 材料科学 材料科学
- 催化剂是一种催化剂.
背景情况:
- 过渡金属复合体是理解表面现象的模型系统.
- 纳米颗粒上的物种对于催化活性至关重要.
- 固态 (2H) NMR是一种强大的技术,用于表征环境.
研究的目的:
- 用2H固态NMR研究过渡金属复合体中的物种.
- 要提取四极合常量 (Qcc) 和不对称参数.
- 建立一种方法来对纳米颗粒表面的物种进行表征.
主要方法:
- 各种过渡金属复合物的合成和表征 (Tp*RuD(THT) 2,Tp*RuD(D2) ((THT),Tp*RuD(D2) 2,Cp*RuD3 ((PPh3),RuD2 ((eta2-D2) 2 ((PCy3) 2).
- 在广泛的温度范围内测量2H固态NMR光谱.
- 对NMR线形的分析,以确定四极合常量 (Qcc) 和不对称参数.
主要成果:
- 四极合常量 (Qcc) 对于金属结合的子在13kHz到76kHz之间.
- 加入碳位置的体显示Qcc值在134kHz至192kHz之间.
- 在室温下一条狭窄的线表示高度移动的子,归因于杂质或D2损失.
结论:
- 测量的四极合常量可以有效地区分各种物种.
- 这种NMR方法提供了一种方法来对Ru-纳米粒子表面的物种进行表征.
- 了解这些物种对于优化基催化剂至关重要.
相关概念视频
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.
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
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...
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
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,...
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...