Inelastic neutron scattering has been used to study the tunnelling of methyl groups belonging to several guest molecules (toluene, p-xylene, gamma-picoline) incarcerated in a host calixarene matrix. In all the cases investigated, the low tunnel-split librational states of the guest methyl groups. The main line occurs near 0.63 meV, very close to the CH3 quantum free rotor limit. In the toluence complex, the quantum regime persists at least up to 60 K. Effects of coupling between rotational and vibrational modes are discussed. Very subtle structural changes not revealed by diffraction measurements are suggested by the neutron spectroscopy results.
Methyl group tunnelling studies in calixarenes / Caciuffo, ROBERTO GIOVANNI MARIA; G., Amoretti; C. J., Carlile; F., Fillaux; Francescangeli, Oriano; M., Prager; F., Ugozzoli. - In: PHYSICA. B, CONDENSED MATTER. - ISSN 0921-4526. - 202 (3-4):(1994), pp. 279-286. [10.1016/0921-4526(94)90306-9]
Methyl group tunnelling studies in calixarenes
CACIUFFO, ROBERTO GIOVANNI MARIA;FRANCESCANGELI, ORIANO;
1994-01-01
Abstract
Inelastic neutron scattering has been used to study the tunnelling of methyl groups belonging to several guest molecules (toluene, p-xylene, gamma-picoline) incarcerated in a host calixarene matrix. In all the cases investigated, the low tunnel-split librational states of the guest methyl groups. The main line occurs near 0.63 meV, very close to the CH3 quantum free rotor limit. In the toluence complex, the quantum regime persists at least up to 60 K. Effects of coupling between rotational and vibrational modes are discussed. Very subtle structural changes not revealed by diffraction measurements are suggested by the neutron spectroscopy results.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
