Magnetic Properties of Complexes

Magnetic Properties of Coordination Compounds

The magnetic properties of a compound can be determined from its electron configuration and the size of its atoms. An electron is a negatively charged particle which revolves around the nucleus and spins on its own axis. A magnetic field is generated due to the orbital motion and spin of the electron. The spinning of an electron in an orbit is very much similar to flow of electric current in a closed circuit. Therefore, an unpaired electron is regarded as a micro magnet which has a definite magnetic moment. Substance having an unpaired electron when placed in a magnetic field interacts with the applied field. Consequently, an attractive force is exerted and the paramagnetic property is shown.

Complexes which tend to move into or interacts a magnetic field is paramagnetic while complexes which tend to move out of a magnetic field is diamagnetic. The extent of paramagnetism is measured in terms of the magnetic moment(μ).
Transition metals have a large number of unpaired electrons in their d-orbital. The size of the magnetic moment of a system containing unpaired electrons is related directly to the number of such electrons. Greater the number of unpaired electrons, larger the magnetic moment (μ). Larger the magnitude of μ, greater the paramagnetism of the compound.
Magnetic moment has contributions from spin and orbital angular momentum. A nonspherical environment may lead to quenching of the contribution from orbital angular momentum.
However, the spin-only magnetic moment applicables in all cases and is related to the total number of unpaired electrons.

Whewe- n = number of unpaired electons in the complex.

If there is a possibility for contribution from the orbital angular momentum, then-

Where-
L = Resultant orbital angular momentum quantum number of all electrons in the complex
S = Resultant spin quantum number of all electrons in the complex.
For an octahedral complex, orbital contributions are possible only when the t_2g orbitals are occupied unsymmetrically and for a tetrahedral complex the t₂ orbitals have to be unsymmetrically occupied.

Calculate the μ_s and μ_L+S values for [V(H₂O)₆]⁺³ system.

Oxidation state of V in the given complex ion is +3 so it is d² system.

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