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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...

Diamagnetism

Diamagnetism

Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.

Ferromagnetism

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...

Paramagnetism

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...

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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Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

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Published on: July 3, 2015

Cobalt(II) single-molecule magnets.

¹WestCHEM, Department of Chemistry, University of Glasgow, University Avenue, G12 8QQ, UK. M.Murrie@chem.gla.ac.uk

Chemical Society Reviews

|April 28, 2010

Summary

This summary is machine-generated.

Polynuclear cobalt(ii) complexes show promise as single-molecule magnets (SMMs). These materials exhibit slow magnetic relaxation, potentially leading to higher operating temperatures than other SMMs.

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Area of Science:

Coordination Chemistry
Magnetochemistry
Materials Science

Background:

Polynuclear cobalt(ii)-based complexes are investigated for their magnetic properties.
Single-molecule magnets (SMMs) are crucial for developing molecular magnetic materials.
Slow magnetic relaxation is a key characteristic of SMMs.

Purpose of the Study:

To review recent advancements in polynuclear cobalt(ii)-based complexes.
To highlight their potential as single-molecule magnets (SMMs).
To compare their magnetic anisotropy with other SMM systems.

Main Methods:

Literature review of polynuclear cobalt(ii) complexes.
Analysis of magnetic relaxation data.
Comparison of magnetic anisotropy origins.

Main Results:

Cobalt(ii) complexes exhibit slow magnetic relaxation at low temperatures.
These complexes demonstrate significant magnetic anisotropy.
Potential for higher blocking temperatures compared to other SMMs.

Conclusions:

Polynuclear cobalt(ii) complexes are promising candidates for high-performance SMMs.
Their magnetic properties stem from large magnetic anisotropies.
Further research could lead to practical applications in molecular magnetism.