magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

, Pascals’ constants are numbers used in the evaluation of the magnetic susceptibilities of

coordination compound A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

s. The magnetic susceptibility of a compound is the sum of the paramagnetic susceptibility associated with the

unpaired electron In chemistry, an unpaired electron is an electron that occupies an orbital of an atom singly, rather than as part of an electron pair. Each atomic orbital of an atom (specified by the three quantum numbers n, l and m) has a capacity to contain ...

s and the opposing

diamagnetic Diamagnetic materials are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted ...

susceptibility associated with

electron pair In chemistry, an electron pair or Lewis pair consists of two electrons that occupy the same molecular orbital but have opposite spins. Gilbert N. Lewis introduced the concepts of both the electron pair and the covalent bond in a landmark paper ...

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/ref> Typically, the paramagnetic susceptibility greatly exceeds in magnitude the diamagnetic susceptibility. Thus, the diamagnetic correction is not considered for many purposes. For more precise analyses, however, the diamagnetic corrections are calculated by summing the contributions from the components of the molecule. These group contributions are Pascal’s constants. This analysis assumes that these group contributions are identical in all molecules. In general, the magnitude of Pascal’s constants correlates with the number of electrons in the groups. Groups with extended pi-delocalization have larger diamagnetic corrections compared to related saturated ligands. These correction factors were first described by in 1910.Pascal, P. Ann. Chim. Phys. 1910, volume 19, page 5 The values and the method of analysis have been revised several times.

Tables

: : : With organic molecules corrections are made for bond types other than C-C and C-H single bonds. :

Notes

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References

Magnetism