Host–guest complexes of cucurbit[8]uril with some pentaerythritol derivative guests

Abstract

A series of first generation dendritic guests from pentaerythritol derivatives have been designed and synthesized. Investigation of the complex structures of cucurbit[8]uril (Q[8]) and the guests based on the ¹H NMR technique have revealed that the host Q[8] selectively included different branch(es) of the first generation dendritic guests and formed inclusion complexes with different structural conformations. The experimental results obtained from electronic absorption spectroscopy showed that the 1 : 1 ratio of Q[8]-based host–guest inclusion complexes have moderate stability with an average formation constants of 10⁴ L mol⁻¹. The single crystal structures of some of the guests (g5 and g6) and Q[8]–guest complexes (Q[8]-g4 and Q[8]-g6) further confirm but in some cases contradict the research results of the ¹H NMR technique and electronic absorption spectroscopy in aqueous solution.