Diamagnetic susceptibility anisotropy

Values of the diamagnetic anisotropy of benzene and other aromatic hydrocarbon molecules are calculated on the basis of the assumption that the p, electrons (one per aromatic carbon atom) are free to move from carbon atom to adjacent carbon atom under the influence of the impressed fields. When combined with the assumed values for the contributions of the other electrons (-2.0X 10-6 for hydrogen, —4.5 X10 c for aromatic carbon, — 6.0XlO-6 for aliphatic carbon) these lead to principal diamagnetic susceptibilities of molecules in approximate agreement with the available experimental data. The diamagnetic anisotropy of graphite is also discussed. 

CERTAIN diamagnetic crystals, such as bismuth and graphite, show pronounced diamagnetic anisotropy, the susceptibility being of normal magnitude in the basal plane and abnormally large in the direction perpendicular to this plane. A similar phenomenon is shown by... 

Magnetic properties. Anisotropy of diamagnetic susceptibility has been used, in much the same way as optical anisotropy, as evidence of molecular orientation in crystals. 

Some diamagnetic crystals (graphite, bismuth, naphthalene and other aromatic substances) show prohounced diamagnetic anisotropy. The observed anisotropy of crystals of benzene derivatives correspond to the molar diamagnetic susceptibility —54 X 10 with the field direction perpendicular to the plane of the benzene ring and —37 X lO"6 with it in the plane. This molecular anisotropy has been found to be of some use in determining the orientation of the planes of aromatic molecules in crystals.1... 

To study the N-1 phase transition, it is necessary to find some physical property proportional to 5(7) that can be measured accurately as a function of temperature. There are many possibilities, which include depolarization of Raman spectra, diamagnetic susceptibility anisotropy, NMR deuterium quadrupole splitting, dielectric constant... 

Aromatic compounds display magnetic properties related to a ring current. These include unusual chemical shifts, especially of protons, large magnetic anisotropies, and large diamagnetic susceptibility exaltations. 

The diamagnetic susceptibility anisotropy (DSA) is linearly related to the binding energy (BE), the correlation being... 

The diamagnetic susceptibility anisotropies and molecular second moments of the electronic charge distributions for COCIF have been calculated by Maksic and Mikac [1303a], and these authors suggested that their calculated values showed that the experimentally derived second moments (calculated from the Zeeman effect in the Stark-modulated microwave... 

The decreasing aromaticity in the anion is also manifested in a smaller magnetic sus-ceptibihty exaltation (A) , which is defined as the difference between the bulk magnetic susceptibility (xm) of a compound and the susceptibility (xm ) estimated from an increment system for the same structure without cyclic conjugation (A = xm — Xm in units of ppm cgs). Thus, the value A = —9.1 for PhO is equal to only 59% of the A = —15.5 for phenol. The computed values for the diamagnetic susceptibility anisotropy (Xanis) follow the same trend, indicating that PhO has actually about 60% of the aromaticity of PhOH352. 

---