A 13C cross-polarisation magic-angle-spinning nuclear magnetic resonance study of some well characterised crown ethers and their complexes

Abstract

Solid crown ethers and crown ether complexes with well determined crystal structures have been examined by ¹³C cross-polarisation magic-angle-spinning (CPMAS) n.m.r. Certain carbon atoms in most of the compounds studied gave single lines in the solution-state spectra, but produced multiplets in the spectra of the solids. Such multiplicities depend on the conformation and packing adopted by the molecules in the solid state and a qualitative discussion is presented of the origins of such splittings in these compounds. The sensitivity of ¹³C CPMAS spectra to subtle structural differences is reflected in the differences between the spectra of two isomorphous complexes.