シナミック酸の [2 + 2] フォトダイメリゼーションにおける一時的な状態: 固体状態のNMRとX線解析の相関
Mujeeb Khan1, Gunther Brunklaus, Volker Enkelmann
1Max-Planck-Institut für Polymerforschung, Postfach 31 48, D-55021 Mainz, Germany.
Journal of the American Chemical Society
|January 15, 2008
まとめ
固体NMRは,トランスシナミック酸光二分子の対称性を歪める非対称な水素結合を明らかにします. このダイナミックな水素結合は,トポケミカル反応を理解するために極めて重要です.
科学分野:
- 固体化学 固体化学
- オーガニック・クリスタログラフィー
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- トランスシナミック酸誘導体は,トポケミカル反応のモデル化合物である.
- 以前の研究では,X線 difraktion,AFM,および振動スペクトロスコピーを利用しました.
- 固体NMRは,反応メカニズムに関する高度な洞察を提供します.
研究 の 目的:
- 固体NMRを用いたトランスシナミック酸誘導体の固体状態反応をモニターする.
- 光二次元の構造的詳細と対称性を明らかにする.
- トポケミカル変換における水素結合の役割を調査する.
主な方法:
- 13C-CPMAS (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) 固体NMRスペクトロスコーピー.
- 単一結晶X線微分分析. 単一結晶X線微分分析. 単一結晶X線微分分析. 単一結晶X線微分分析. 単一結晶X線微分分析. 単一結晶X線微分分析. 単一結晶X線微分分析.
- 高温X線微分. 高温X線微分. 高温X線微分. 高温X線微分. 高温X線微分. 高温X線微分. 高温X線微分.
主要な成果:
- 観測されたNMR信号は,初期X線 difraktion予想に反して,非中心対称フォトジマーを示した.
- 包装効果ではなく,非対称な水素結合が,NMRスペクトルのピーク分裂を引き起こした.
- ダイナミックな水素結合は,高温X線データによって証明されました.
結論:
- 非対称な水素結合は,シナミック酸光二酸化物における局所的対称性を著しく歪める.
- 似たような温度でX線 difraktionと固体NMRを組み合わせることは,トポケミカル反応におけるダイナミックな過程の特徴づけに不可欠です.
- この研究は,有機固体変異の反応機構の詳細な洞察を提供します.
さらに関連する動画
10:03Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
09:57Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
関連する概念動画
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...
01:25Deactivation Processes: Jablonski Diagram
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
01:192D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)
Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
01:12Two-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.
01:162D 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...
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.