Dimerization Control in the Self-Assembly Behavior of Copillar[5]arenes Bearing ω-Hydroxyalkoxy Groups

Two novel copillar[5]arenes bearing omega-hydroxyalkoxy groups are synthesized and their self assembly properties are studied by H-1 NMR spectroscopy, specific viscosity, and X-ray measurements. The copillar[S]arene 2b bearing a 6-hydroxyhexyloxy group exhibits a reversible self assembly behavior, leading to the formation of the self inclusion monomer and hugging dimers. The reversible self assembly behavior can be controlled by tuning solvent, temperature, guest, and H-bond interaction. However, the copillar[5]arene 2a bearing a short 4-hydroxybutyloxy group does not show such a self-assembly behavior to the formation of the self-inclusion monomer and hugging dimers.