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Related Concept Videos

Colors and Magnetism03:02

Colors and Magnetism

Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
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...
Ferromagnetism01:31

Ferromagnetism

Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
Paramagnetism01:30

Paramagnetism

Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
Crystal Field Theory - Octahedral Complexes02:58

Crystal Field Theory - Octahedral Complexes

Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

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Related Experiment Video

Updated: Jun 2, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
08:55

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

[4Fe4S]2+ clusters exhibit ground-state paramagnetism.

Kresimir Rupnik1, Chi Chung Lee, Yilin Hu

  • 1Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70808, USA.

Journal of the American Chemical Society
|April 15, 2011
PubMed
Summary
This summary is machine-generated.

Two nitrogen fixation proteins possess unique ferredoxin-type clusters. These clusters exhibit an unusual paramagnetic state upon oxidation, suggesting a specific function and evolutionary link.

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Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
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Last Updated: Jun 2, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
08:55

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Published on: June 7, 2018

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope
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Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
06:53

Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks

Published on: June 9, 2023

Area of Science:

  • Biochemistry
  • Bioinorganic Chemistry
  • Molecular Biology

Background:

  • Ferredoxins are crucial electron transfer proteins containing iron-sulfur clusters.
  • Nitrogen fixation is a vital biological process essential for life on Earth.
  • The electronic properties of iron-sulfur clusters dictate their function in biological systems.

Purpose of the Study:

  • To investigate the unique properties of ferredoxin-type [4Fe4S] clusters in nitrogen fixation proteins.
  • To understand the implications of these unique properties for the mechanism of nitrogen fixation.
  • To explore potential evolutionary relationships between these clusters.

Main Methods:

  • Spectroscopic analysis of the [4Fe4S] clusters.
  • Electrochemical studies to determine redox properties.
  • Bioinformatic analysis to compare cluster structures.

Main Results:

  • Identified ferredoxin-type [4Fe4S] clusters in two nitrogen fixation proteins.
  • Observed a paramagnetic ground state upon oxidation, a novel characteristic for ferredoxins.
  • Demonstrated a unique electronic coupling within these clusters.

Conclusions:

  • The unusual paramagnetic state is critical for the function of these clusters in nitrogen fixation.
  • These findings suggest a specialized role and evolutionary origin for these [4Fe4S] clusters.
  • The study opens new avenues for understanding nitrogenase mechanisms.