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相关概念视频

Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

1.5K
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...
1.5K
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.4K
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,...
1.4K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.5K
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 involved orbitals. The...
1.5K
π Electron Effects on Chemical Shift: Overview01:27

π Electron Effects on Chemical Shift: Overview

1.6K
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,...
1.6K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

1.6K
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...
1.6K
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

3.0K
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...
3.0K

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Updated: Jan 18, 2026

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
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视角:基于轨迹的激发状态动态的振动式合潜力.

Sandra Gómez1, Patricia Vindel-Zandbergen2,3, Dilara Farkhutdinova4,5

  • 1Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.

Journal of chemical theory and computation
|September 11, 2025
PubMed
概括
此摘要是机器生成的。

振动合 (VC) 潜能简化了兴奋状态动态模拟,使光物理过程的有效研究成为可能. 这些模型为复杂系统中的能量转移和放松通路提供了宝贵的见解.

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科学领域:

  • 计算化学计算化学
  • 物理化学 物理化学
  • 理论化学 理论化学

背景情况:

  • 激发状态动力学模拟对于理解光物理和光化学过程至关重要.
  • 非adiabatic的相互作用需要准确的,但计算可处理的模型.
  • 振动性合 (VC) 潜能提供了一个基于物理的方法来建模这些相互作用.

研究的目的:

  • 在基于轨迹的兴奋状态动态模拟中审查振动合 (VC) 潜力的应用.
  • 突出使用风险投资模型,特别是线性风险投资 (LVC) 获得的优势和见解.
  • 讨论与各种计算方法集成的VC潜力.

主要方法:

  • 审查振动合 (VC) 潜力,包括线性VC (LVC).
  • 与基于轨迹的方法的集成:表面跳跃,变化的多配置高斯式和精确因子推算衍生方法.
  • 适用于分子和凝结相系统.

主要成果:

  • 虚拟电路模型,特别是LVC,有助于对光物理和光化学过程进行高效的模拟.
  • 这些模型提供了对能量/电荷转移,兴奋状态寿命和放松途径的洞察.
  • 虚拟机模型已经揭示了机械细节,如特定状态的系统间交叉和振动模式选择性.

结论:

  • 虚拟电路潜能在计算上是高效的,对于基准测试和探索兴奋状态动态非常有价值.
  • 未来的方向包括将VC与机器学习,无调校正和复杂环境的混合QM/MM框架集成在一起.
  • 基于VC的方法增强了对不同分子系统的光物理学的研究.