ダイナミックな核極化NMRスペクトロスコピーは,微細な有機ポリマーの高通量特徴を可能にします
Frédéric Blanc1, Samantha Y Chong, Tom O McDonald
1Department of Chemistry, §Stephenson Institute for Renewable Energy, and ‡Center for Materials Discovery, University of Liverpool , Crown Street, Liverpool L69 7ZD, United Kingdom.
Journal of the American Chemical Society
|September 14, 2013
まとめ
動的核極化 (DNP) 固体NMRは,微細な有機ポリマーの信号対ノイズ比を大幅に高めます. この高度な技術により,分子構造の詳細な決定とポリマーライブラリの高通量特徴づけが可能です.
科学分野:
- マテリアルサイエンス 材料科学
- ポリマー化学のポリマー化学について
- アナリティカル・ケミストリー (Analytical Chemistry) とは
背景:
- 微孔性有機ポリマーは,構造的特徴が難しい複雑なネットワークです.
- 固体核磁共振 (NMR) スペクトロスコピーは,ポリマー構造を分析する上で極めて重要です.
- 伝統的なNMR方法は,しばしば感度が低く,詳細な分析を制限しています.
研究 の 目的:
- 微孔性の有機ポリマーの特性改善のために,強化された固体NMRのダイナミック・ニュクレア・ポラライゼーション (DNP) を適用する.
- 自然に豊富に存在する (13) C と (15) N のクロス・ポラライゼーション・マジック・アングル・スピニング (CP MAS) NMRスペクトルの高い信号対ノイズ比を達成するために.
- ポリマーライブラリを効率的かつ高速に分析できるようにする.
主な方法:
- ダイナミック・ニュクレア・ポラライゼーション (DNP) を利用し,ビス・ニトロキシード・ラジカルを用いた.
- 固体核磁共振 (NMR) スペクトロスコーピー,特に (13) C と (15) N CP MAS を採用しました.
- 高磁場 (14.1 T) と低温 (∼105 K) で実験を行った.
主要な成果:
- 10倍以上の感度向上を達成しました.
- 高品質の自然多量 (13)Cと (15)NのCP MASのNMRスペクトルを取得しました.
- 複雑なポリマーネットワークの分子構造に関する前例のない詳細を明らかにした.
結論:
- DNP固体NMRは,微細な有機ポリマーの詳細な構造分析のための強力な技術です.
- この方法は,組み合わせポリマーライブラリを効率的かつ高通量で特徴づけることを容易にする.
- このアプローチは,複雑なポリマー材料の研究を大幅に前進させる.
関連する概念動画
¹H 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...
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
Two-Dimensional (2D) NMR: Overview
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
Other Nuclides: 31P, 19F, 15N NMR
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
2D NMR: Overview of Homonuclear Correlation Techniques
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
COSY90 is the standard two-dimensional (2D) COSY experiment that...
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...


