MOLECULAR TUNNELING IN P-TERT-BUTYLCALIX[4]ARENE(2 1)P-XYLENE/

Inelastic neutron scattering has been used to study molecular tunnelli ng in the p-tert-butylcalix[4]arene(2:1)p-xylene complex. At low tempe rature the measured spectra show several bands between 0.63 and 2.6 me V which are interpreted as being due to transitions between tunnel-spl it librational states of the p-xylene methyl groups. Effects of coupli ng between a CH3 group and the whole p-xylene molecule have been obser ved. The rotational barrier provided by the host lattice is very small and the methyl groups behave as almost free quantum rotors.