Guest-Assisted and Guest-Inhibited Shell Closures Provide Differently Shaped Carceplexes and Hemicarceplexes¹^,²

Abstract

The syntheses are reported of ten new carceplexes, hemicarceplexes, or their free hosts by coupling different or similar pairs of cavitands at their rims with four O(CH2)nO or four m-(OCH2)2C6H4 bridging groups. Different combinations of seven different cavitands and five different bridging groups were involved in the shell closures, whose yields ranged from 50 to 1.8%. Seven of the new hosts have like northern and southern hemispheres, whereas three possess differently shaped hemispheres. The yield patterns are interpreted in terms of complexing guest preorganizing the reaction partners for shell closure, or the reaction partners complexing each other in nonproductive binding which inhibits shell closure. Crystal structures are reported for one new cavitand, one new caviplex, and three new hemicarceplexes. Comparisons of changes in 1H NMR spectra of incarcerated guests in different hosts provide interesting correlations of chemical shifts with structure.