Guest-encapsulation behavior in a self-assembled heterodimeric capsule

Tetra(4-pyridyl)-cavitand 1 and tetrakis(4-hydroxyphenyl)-cavitand 2 self-assemble into a heterodimeric capsule 1.2 via four PhOH center dot center dot center dot pyridyl hydrogen bonds in CDCl3, wherein one molecule of 1,4-disubstituted-benzene as a guest is encapsulated to form a ternary complex, guest@(1.2). The X-ray crystallographic analysis of (methyl p-ethoxybenzoate)@(1.2) confirmed that the methyl ester and ethoxy groups of the encapsulated guest are oriented to the cavity ends of the 1 and 2 units, respectively. The scope and limitation of guest encapsulation in 1.2, including guest-binding selectivity and orientational isomeric selectivity, are described from the viewpoint of size complementarity and CH-pi, CH-halogen, and halogen-pi interactions between guest and the cavity of 1.2. (C) 2008 Elsevier Ltd. All rights reserved.