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Related Concept Videos

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

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

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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,...
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NMR Spectroscopy: Spin–Spin Coupling01:08

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

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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.
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1.1K
Spin–Spin Coupling Constant: Overview01:08

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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.
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¹H NMR Signal Multiplicity: Splitting Patterns01:13

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5.3K
When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...
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Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
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Exchange Spin Coupling in Optically Excited States.

Torben Steenbock1, Lawrence L M Rybakowski1, Dominik Benner1

  • 1Department of Chemistry, University of Hamburg, HARBOR, Building 610, Luruper Chaussee 149, Hamburg 22761, Germany.

Journal of Chemical Theory and Computation
|July 7, 2022
PubMed
Summary
This summary is machine-generated.

We developed a new method to measure spin coupling in optically excited states of molecules. This technique accurately predicts spin interactions, aiding quantum information processing applications.

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Area of Science:

  • Quantum Chemistry
  • Materials Science
  • Spectroscopy

Background:

  • Electron spin coupling in optically excited states influences molecular photoemission properties.
  • This spin coupling is crucial for potential quantum information processing applications.
  • Experimental studies show photogenerated spins in metal complexes interact with attached radicals, affecting spin density distributions.

Purpose of the Study:

  • To propose and validate a computational method for evaluating spin coupling in optically excited states.
  • To investigate the tunability of spin coupling in metal complexes by altering metal centers.
  • To identify and characterize previously unconsidered excited states and their properties.

Main Methods:

  • Utilized an energy-difference scheme to evaluate spin coupling.
  • Employed unrestricted and spin-flip simplified time-dependent density functional theory (TD-DFT).
  • Applied the method to three experimentally studied platinum complexes for validation.

Main Results:

  • Computed coupling constants showed excellent agreement with experimental data.
  • Demonstrated that spin coupling can be fine-tuned by substituting platinum with palladium or zinc.
  • Identified a third bright excited doublet state with inverse spin polarization and significantly higher brightness compared to previously known states.

Conclusions:

  • The proposed TD-DFT-based energy-difference scheme is a reliable method for evaluating spin coupling in optically excited states.
  • Metal substitution offers a viable strategy for tuning spin coupling in these systems.
  • The newly identified bright excited state has potential for applications in optical spin control and quantum information transfer.