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Spin–Spin Coupling: One-Bond Coupling

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,...

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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.
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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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Colors and Magnetism

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Color in Coordination Complexes
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Valence Bond Theory

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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...

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Related Experiment Video

Updated: Oct 6, 2025

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

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Spin Crossover in a Cobalt Complex on Ag(111).

Sven Johannsen¹, Sascha Ossinger^2,3, Jan Grunwald²

¹Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098, Kiel, Germany.

Angewandte Chemie (International Ed. in English)

|January 15, 2022

Summary

This summary is machine-generated.

Cobalt complexes on silver surfaces exhibit reversible spin-state transitions. These changes, controlled by electrical current, offer insights into electron-induced excited spin-state trapping (ELIESST) mechanisms.

Keywords:

Electron Transfer Molecular Devices Scanning Probe Microscopy Single-Molecule Studies Spin Crossover

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Area of Science:

Surface science
Molecular magnetism
Scanning probe microscopy

Background:

Cobalt complexes with specific coordination spheres can exhibit interesting magnetic properties.
Controlling and observing spin states at the single-molecule level is a key challenge in molecular magnetism.

Purpose of the Study:

To investigate the spin states of a Co-based complex deposited on Ag(111) using scanning tunneling microscopy.
To understand the mechanism of electron-induced excited spin-state trapping (ELIESST) in molecular systems.

Main Methods:

Deposition of a Co-based complex [Co(H2B(pz)(pypz))2] on Ag(111) surface.
Investigation using scanning tunneling microscopy (STM) at low temperatures (≈5 K).
Analysis of molecular transitions induced by tunneling current and bias voltage.

Main Results:

Molecules aggregate into tetramers due to their coordination sphere.
Individual complexes exhibit reversible transitions between two states, interpreted as S=1/2 and S=3/2 spin states.
Transition rates depend linearly on tunneling current and show bias voltage dependence.

Conclusions:

The observed bistability is attributed to the different spin states of the Co2+ complex.
Calculated orbital structures support the interpretation of the spin states and switching mechanism.
Provides initial insights into the ELIESST mechanism at the single-molecule level.