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Related Concept Videos

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

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

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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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Radical Formation: Overview01:03

Radical Formation: Overview

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A bond can be broken either by heterolytic bond cleavage to form ions or homolytic bond cleavage to yield radicals. A fishhook arrow is used to represent the motion of a single electron in homolytic bond cleavage. There are two main sources from which radicals can be formed:
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the...
2.1K
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.0K
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,...
1.0K
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

959
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...
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Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–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...
1.1K
Radical Formation: Addition00:47

Radical Formation: Addition

1.7K
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
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<i>S</i>-Oxide <i>peri</i>-Annulated Blatter Radicals: A Paradigm for Chiral Radicals.

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Azahelicene-fused Blatter radicals: chiral paramagnetic NIR absorbers.

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Raising the HOMO level of the [<i>closo</i>-B<sub>10</sub>H<sub>10</sub>]<sup>2-</sup> anion: apical alkyl derivatives for modern materials.

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Ladder-Type Cu(II) Coordination Polymer with π-π Stacking of Planar Blatter Radical Ligands: Structural and Magnetic Characterization.

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Photocyclization of 8-Aryloxybenzo[<i>e</i>][1,2,4]triazines Revisited: Unambiguous Structural Assignment of Planar Blatter Radicals by Correlation NMR Spectroscopy.

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Related Experiment Video

Updated: Jul 19, 2025

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
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Blatter Diradicals with a Spin Coupler at the N(1) Position.

Dominika Pomikło1, Piotr Kaszyński1,2,3

  • 1Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363, Łódź, Poland.

Chemistry (Weinheim an Der Bergstrasse, Germany)
|August 18, 2023
PubMed
Summary

Researchers synthesized stable di-Blatter diradicals using benzo[e][1,2,4]triazine and dilithiobenzenes. The spin coupling unit, like phenylene, controlled the singlet-triplet energy gap, crucial for magnetic applications.

Keywords:
EPR spectroscopydensity functional calculationsdiradicals

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Area of Science:

  • Organic Chemistry
  • Materials Science
  • Quantum Chemistry

Background:

  • Blatter diradicals are organic molecules with two unpaired electrons.
  • Controlling the spin state (singlet or triplet) is key for their potential applications.

Purpose of the Study:

  • To synthesize and characterize novel di-Blatter diradicals.
  • To investigate the effect of different arylene coupling units on the diradical's electronic properties.
  • To determine the singlet-triplet energy gap (ΔES-T) and its tunability.

Main Methods:

  • Synthesis of diradicals from benzo[e][1,2,4]triazine and dilithiobenzenes.
  • Electrochemical analysis to study redox processes.
  • Electron Paramagnetic Resonance (EPR) spectroscopy at variable temperatures.
  • Density Functional Theory (DFT) calculations.

Main Results:

  • Successful synthesis of di-Blatter diradicals linked by 1,4-phenylene and 1,3-phenylene units.
  • Observation of four one-electron redox processes in both diradicals.
  • Determination of singlet-triplet energy gaps: -3.02(11) kcal/mol for 1,4-phenylene and -0.16(1) kcal/mol for 1,3-phenylene derivatives.
  • Conformational effects influenced the energy gap in the 1,3-phenylene derivative.

Conclusions:

  • A straightforward method for accessing stable Blatter diradicals with tunable spin properties was developed.
  • The choice of arylene coupling unit significantly impacts the singlet-triplet energy gap.
  • DFT calculations suggest that low LUMO energy of (het)arylenes stabilizes the triplet state.