パラ水素から派生したスピン順序を低磁場でのピリジンに自発的に移す
Kevin D Atkinson1, Michael J Cowley, Paul I P Elliott
1Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingdom.
Journal of the American Chemical Society
|September 2, 2009
まとめ
この研究では,ハイパーポラライズドピリジンの検出を容易にする新しいイリジウム複合体の詳細が示されています. パラヒドロゲン誘発の偏振は,自由ピリジンに対するNMRスペクトロスコピーの100倍以上の信号増強を可能にします.
科学分野:
- 有機金属化学 有機金属化学
- 無機化学 無機化学とは
- NMRスペクトロスコーピ NMRスペクトロスコーピ
背景:
- カチオンイリジウム複合体は貴重な触媒である.
- リンガンド交換ダイナミクスは,触媒過程において極めて重要です.
- パラ水素誘発極化 (PHIP) は,NMR信号を強化する.
研究 の 目的:
- 新しいカチオンのイリジウム二酸化水素複合体を合成し,特徴づけること.
- ディヒドリド複合体のリガンド交換機構を調査するために.
- NMRスペクトロスコピーにおける信号増強のためのPHIPの応用を実証する.
主な方法:
- [Ir (((COD)) (((PCy (((3))) (((py)) ]BF (((4) と fac,cis-[Ir (((PCy (((3)))) (((py)) (((3) ((H)) (((2)) ]BF (((4) の合成について
- メタノールにおけるピリジンリガンド交換の運動学的研究.
- NMR光譜を用いたパラヒドロゲン誘発極化 (PHIP) 実験.
主要な成果:
- イリジウム二水素複合体 (2) が形成され,特徴づけられました.
- 活化パラメータを決定したピリジンリガンドのトランスからヒドリドへの急速な交換が観察されました.
- フリーピリジン共鳴 (1H, 13C, 15N) の100倍以上の信号強化がPHIPで達成されました.
- 信号の強化は,フォスフィンリガンドの特性と磁場強度によって影響を受けた.
結論:
- 開発されたイリジウム複合体は,PHIPのための効果的なプラットフォームとして機能します.
- PHIPは,リガンド交換を通じてピリジンの感受性の高い検出を可能にします.
- この方法は,ソリューションにおけるダイナミックなプロセスを研究するための強力なツールを提供します.
関連する概念動画
π Electron Effects on Chemical Shift: Overview
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0, resulting in...
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
Atomic Nuclei: Nuclear Magnetic Moment
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
Paramagnetism
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
Atomic Nuclei: Nuclear Spin State Overview
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...
¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
![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)

