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The element hydrogen is virtually never called 'paramagnetic' because the monatomic gas is stable only at extremely high temperature; H atoms combine to form molecular H 2 and in so doing, the magnetic moments are lost (quenched), because of the spins pair. Hydrogen is therefore diamagnetic and the same holds true for many other elements ...
Hund's rule states that when there are several MO's with equal energy, the electrons occupy the MO's one at a time before two electrons occupy the same MO. The filled MO highest in energy is called the highest occupied molecular orbital (HOMO) and the empty MO just above it is then the lowest unoccupied molecular orbital (LUMO).
The difference between the chemical shift of a given nucleus in a diamagnetic vs. a paramagnetic environment is called the hyperfine shift.In solution the isotropic hyperfine chemical shift for nickelocene is −255 ppm, which is the difference between the observed shift (ca. −260 ppm) and the shift observed for a diamagnetic analogue ferrocene (ca. 5 ppm).
Magnetic susceptibility indicates whether a material is attracted into or repelled out of a magnetic field. Paramagnetic materials align with the applied field and are attracted to regions of greater magnetic field. Diamagnetic materials are anti-aligned and are pushed away, toward regions of lower magnetic fields.
The ortho and para forms of water have recently been isolated. Para water was found to be 25% more reactive for a proton-transfer reaction. [28] [29] Molecular oxygen (O 2) also exists in three lower-energy triplet states and one singlet state, as ground-state paramagnetic triplet oxygen and energized highly reactive diamagnetic singlet oxygen.
Diamagnetic materials, like water, or water-based materials, have a relative magnetic permeability that is less than or equal to 1, and therefore a magnetic susceptibility less than or equal to 0, since susceptibility is defined as χ v = μ v − 1. This means that diamagnetic materials are repelled by magnetic fields.
The Euler relation for a paramagnetic system is then: = + + and the Gibbs-Duhem relation for such a system is: S d T − V d P + I d B e + N d μ = 0 {\displaystyle SdT-VdP+IdB_{e}+Nd\mu =0} An experimental problem that distinguishes magnetic systems from other thermodynamical systems is that the magnetic moment can't be constrained.
Electron transfer self-exchange rates can be also determined with the experimental value of line-width and chemical shift. [3] Sharp peaks of diamagnetic compounds can be broadened during the electron transfer with its partner paramagnetic compound (one-electron oxidized species), since paramagnetic compounds exhibit broader peaks at a different chemical shift.