General Information. All solvents were reagent grade. Silica gel (230-400 mesh) was used for flash chromatography purifications. 1 H NMR spectra were recorded at 400 or 600 MHz and mean value with the smallest and largest association constants determined. In the cases where free host and free guest could not be observed at the same time over the course of the titration, the association constant is too high to be determined precisely (log Ka > 5).