Noble Gases as Magnetic Probes in Fullerene Chemistry

Local aromaticity mapping in the vicinity of planar and nonplanar molecules

“…We also reported on the use of 3 He nuclear magnetic shielding to verify experimentally the magnitude of theoretically calculated NICS parameters in dimeric benzene‐He, pyrrole‐He, and carbazole‐He complexes . Helium‐3 atom is a perfect magnetic probe because it is small, it is chemically inert, and its electron cloud is easily polarized and deformed in the vicinity of π‐electrons above and below planar and nonplanar rings of aromatic molecules . As a result, different shielding or deshielding effects of its nucleus with spin ½ have been calculated.…”

“…As a result, the observed chemical shifts of narrow lines in 3 He NMR spectra allowed discrimination of fullerenes differing by size and symmetry. These experiments were successfully modeled quantitatively at HF, DFT, and MP2 levels of theory …”

“…[32,50,51] Helium-3 atom is a perfect magnetic probe because it is small, it is chemically inert, and its electron FIGURE 1 Schematic image of (a) benzene ring in Cartesian coordinates with p z orbitals forming delocalized π-bonds and magnetic probe moving upward from the ring center and with (b) funnel-shaped deshielding and shielding zones shown cloud is easily polarized and deformed in the vicinity of π-electrons above and below planar and nonplanar [52] rings of aromatic molecules. [8][9][10]12,53] As a result, different shielding or deshielding effects of its nucleus with spin ½ have been calculated. It was predicted that the effective magnetic field at helium nuclei in the presence of aromatic compounds slightly differs from that of free gas.…”

“…These experiments were successfully modeled quantitatively at HF, DFT, and MP2 levels of theory. [53][54][55] The 3 He NMR spectral range is moderate. Very small chemical shift is observed for helium in He 2 and benzene-He dimers.…”

Gas‐phase 21Ne NMR studies and the nuclear magnetic dipole moment of neon‐21

“…Neon‐21 nucleus (spin number I = 3/2 + , state 1 g 9/2 ) has 10 protons and 11 neutrons and thus differs by one nucleon from the magic number 20. It is the fifth most abundant element in the universe but only makes a 0.001818% contribution (by volume) to the atmosphere of Earth, and as a noble gas, its stable compounds are rare; for instance, it forms noncovalent compounds: clathrates and endohedral fullerenes . Neon possesses 14 isotopes with mass numbers from 16 up to 29.…”