Dynamics of Chloromethanes in Cryptophane-E Inclusion Complexes:  A ²H Solid-State NMR and X-ray Diffraction Study

Abstract

In this paper, we present a variable temperature 2H solid-state NMR investigation of cryptophane-E:chloroform and cryptophane-E:dichloromethane inclusion complexes. The 2H line shapes and nuclear spin relaxation rates were analyzed in terms of the distribution of C−D bond orientations and the time scale of the guest dynamics. It was found that encaged chloroform produces broad 2H spectra, and that its reorientation is relatively slow with a correlation time of ∼0.17 μs at 292 K. In contrast, the 2H line shapes of encaged dichloromethane are narrow and the motion of this guest molecule is fast with a correlation time of ∼1.4 ps at 283 K. The 2H NMR data were complemented by an X-ray diffraction study of the cryptophane-E:dichloromethane structure, which was utilized in the analysis of the NMR parameters