Guest-Driven Control of Folding in a Crown-Ether-Functionalized ortho -Phenylene.

A crown-ether-functionalized o -phenylene tetramer has been synthesized and coassembled with monotopic and ditopic, achiral and chiral secondary ammonium ion guests. NMR spectroscopy shows that the o -phenylene forms both 1:1 and 1:2 complexes with monotopic guests while remaining well-folded. Binding of an elongated ditopic guest, however, forces the o -phenylene to misfold by pulling the terminal rings apart. A chiral ditopic guest biases the o -phenylene twist sense.