間接的な核スピン-スピンカップリングにおける"スルー・スペース"と"スルー・ボンド"の貢献を区別する:複合的なPPとPSeスケーラーカップリングに適用される一般的アプローチ
Olga L Malkina1, Jean-Cyrille Hierso2,3, Vladimir G Malkin1
1Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 84 536, Slovakia.
Journal of the American Chemical Society
|June 10, 2022
まとめ
核のスピン・スピン結合経路を 複雑な分子で分析するために 新しい計算方法を開発しました これらのツールは,核磁共振現象の理解を向上させる"空間を通る"と"結合を通る"相互作用を視覚化し,定量化します.
科学分野:
- コンピュータ化学
- 核磁気共鳴スペクトル
- 量子化学について
背景:
- NMRでは間接的な核スピン-スピン結合が重要ですが,複雑なシステムでは十分に理解されていません.
- "透き通る空間" (TS) と"透き通る結合"の結合経路を区別することは困難です.
- 既存の方法は複数の相互作用を含む複雑な結合メカニズムを解剖するのに苦労しています
研究 の 目的:
- 間接的な核スピン-スピン結合経路を分析するための新しい計算アプローチを開発し,検証する.
- 個々の伝達経路とそのJ値への貢献を視覚化,議論,定量化する.
- スピン・スピンカップリングにおける単一のペアと混合結合/非結合相互作用の役割を明らかにする.
主な方法:
- 占有分子軌道 (FOMO) とグローバル分子軌道貢献 (GMOC) に焦点を当てた2つの補完的な理論的アプローチを導入した.
- FOMOは,占有軌道からの貢献を分析し,GMOCは,クロス貢献を含む,占有軌道と空の軌道の両方を考慮します.
- これらの方法をディフォスフィンモデルに適用し,セレナ化 (ディフォスフィノ) ナフタレン化合物の結合を実験的に測定した.
主要な成果:
- 計算ツールによって 個々のスピン・スピン結合経路を 視覚化・定量化することができました
- TSのスピン・スピン伝播におけるリンとセレニウム単体ペアの重要な役割に関する証拠が見つかりました.
- この研究では,近隣のヘテロ原子間の単一対の重複を伴う共振結合を混合するスピン-スピン伝達経路を初めてモデル化しました.
結論:
- 開発されたFOMOとGMOC方法は,複雑なNMR結合メカニズムを解剖するための強力なツールを提供します.
- これらのアプローチは,スピン・スピン・カップリングの理解,特に単一のペアと混合経路の貢献を強化します.
- この発見は,近隣のヘテロアトムを持つ分子における電子構造と結合に関する新しい洞察を提供します.
さらに関連する動画
関連する概念動画
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
1.2K
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...
1.2K
01:08NMR Spectroscopy: Spin–Spin Coupling
1.7K
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
1.7K
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
1.1K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
1.1K
01:17Spin–Spin Coupling: One-Bond Coupling
1.1K
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,...
1.1K
01:08Spin–Spin Coupling Constant: Overview
1.0K
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...
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...
1.0K
01:27¹H NMR: Long-Range Coupling
2.0K
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
2.0K