Chlorine-35 NQR and 1H NMR study of guest structure anddynamics in the thiourea-hexachloroethane inclusion compound

Abstract

Atom-atomic potential calculation of the channel non-stoichiometricthiourea-hexachloroethane inclusion compound shows that the structure of theguest sublattice comprises two types of finite molecular chain, havingdifferent structure and separated by domain walls. In the present paper wepresent results of 35Cl NQR and 1H NMR measurements ofthiourea-hexachloroethane, [2.95(NH2)2CS]C2Cl6,in the temperature range from 7.5 to 90 K, which confirm this model and showthe existence of such a state at least below 60 K. Two resonances in the NQRspectra were assigned to the two nearly commensurate regions, while the thirdresonance, showing an anomalous behaviour, was attributed to the guestmolecules in the domain wall. The observed structure results from thedifferent periodicity of the guest and host substructures and shows adifference from conventional continuum models of the incommensurate state.Propagation motion of the domain wall over the channel is discussed.