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Related Concept Videos

Valence Bond Theory02:42

Valence Bond Theory

Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

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

Spin–Spin Coupling Constant: Overview

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

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

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

NMR Spectroscopy: Spin–Spin Coupling

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

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

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...

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Related Experiment Video

Updated: May 26, 2026

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface
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Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

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Chiral Covalent Organic Framework for Highly Efficient Spin Polarization.

Enbing Zhang1, Shuaishuai Ding1, Guangyuan Feng1

  • 1State Key Laboratory of Advanced Materials for Intelligent Sensing, Key Laboratory of Organic Integrated Circuit, Ministry of Education & Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, School of Science, Tianjin University, Tianjin 300072, China.

Journal of the American Chemical Society
|May 25, 2026
PubMed
Summary

Highly crystalline two-dimensional chiral covalent organic frameworks (2D-CCOFs) enable high spin polarization for chiral spintronic devices. Stable devices were constructed using graphene, demonstrating chirality-dependent magnetoresistance.

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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Area of Science:

  • Materials Science
  • Organic Chemistry
  • Condensed Matter Physics

Background:

  • Two-dimensional chiral covalent organic frameworks (2D-CCOFs) offer potential for chiral spintronic applications due to tunable semiconducting properties and inherent chirality.
  • Key challenges include synthesizing highly crystalline 2D-CCOF films and developing stable device architectures.

Purpose of the Study:

  • To synthesize a highly crystalline and conductive 2D-CCOF film.
  • To construct stable 2D-CCOF-based spintronic devices and evaluate their performance.
  • To investigate the role of graphene as a protective layer in device fabrication.

Main Methods:

  • Synthesis of a high-crystallinity 2D-CCOF film.
  • In situ magnetic conductive-probe atomic force microscopy (mCP-AFM) for characterization.
  • Fabrication of half-spin valve devices using 2D-CCOF and graphene.

Main Results:

  • Successful synthesis of a highly crystalline and conductive 2D-CCOF film.
  • Demonstration of high chiral-induced spin selectivity (CISS) (>90% spin polarization at room temperature).
  • Construction of stable graphene-protected 2D-CCOF spintronic devices exhibiting chirality-dependent magnetoresistance.

Conclusions:

  • The developed 2D-CCOF exhibits excellent spin selectivity, paving the way for efficient spin control.
  • Stable solid-state chiral spintronic devices can be realized using 2D-CCOFs with graphene interlayers.
  • This work addresses critical challenges in 2D-CCOF film synthesis and device fabrication.