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Colors and Magnetism

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 Theory

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...

Crystal Field Theory - Octahedral Complexes

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...

Structural Isomerism

Structural Isomerism

Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...

Coordination Number and Geometry

Coordination Number and Geometry

For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.

Metal-Ligand Bonds

Metal-Ligand Bonds

The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...

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Related Experiment Video

Updated: May 28, 2026

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

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

Published on: June 7, 2018

Magnetostructural D correlations in hexacoordinated cobalt(II) complexes.

Ján Titiš¹, Roman Boča

¹Department of Chemistry (FPV), University of SS. Cyril and Methodius, SK-917 01 Trnava, Slovakia. jan.titis@ucm.sk

Inorganic Chemistry

|October 28, 2011

Summary

This study reveals a magnetostructural correlation in cobalt(II) complexes. Magnetic anisotropy (D) is linked to the distortion of coordination polyhedra in these hexacoordinated cobalt(II) compounds.

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Area of Science:

Inorganic Chemistry
Solid-State Chemistry
Magnetochemistry

Background:

Hexacoordinated cobalt(II) complexes exhibit diverse structural and magnetic properties.
Understanding the relationship between structure and magnetism is crucial for designing new materials.

Purpose of the Study:

To investigate the magnetostructural correlation in mononuclear cobalt(II) complexes.
To correlate magnetic anisotropy (D) with the structural distortion of coordination polyhedra.

Main Methods:

Synthesis and characterization of cobalt(II) complexes with N/O-donor ligands.
Magnetochemical investigations using SQUID susceptibility and magnetization measurements down to 2 K.
Analysis of magnetic data using crystal-field theory.

Main Results:

Investigated complexes with chromophores including {CoN(6)}, {CoO(6)}, {CoO(4)O'(2)}, {CoN(2)O(2)O'(2)}, and {CoN(2)O(2)Cl(2)}.
Observed magnetic behavior typical for zero-field-splitting systems in most complexes.
Established a correlation between magnetic anisotropy (D) and structural distortion.

Conclusions:

The magnetostructural correlation in hexacoordinated cobalt(II) complexes is established.
Magnetic anisotropy parameters are directly related to the splitting of crystal-field multiplets.
Crystal-field theory provides a framework for understanding this relationship.