Formation of Discrete, Functional Assemblies and Informational Polymers through the Hydrogen-Bonding Preferences of Calixarene Aryl and Sulfonyl Tetraureas
journal contributionposted on 02.04.1998, 00:00 by Ronald K. Castellano, Julius Rebek
Derivatives of the calixarenes in the cone conformation featuring either aryl urea or sulfonyl urea functions on their larger (upper) rims dimerize through hydrogen bonding to give molecular capsules. The capsules act as hosts that reversibly bind smaller molecule guests in organic media. Heterodimers form when both aryl and sulfonyl ureas are present, and the heterodimers form exclusively with respect to the homodimers. The heterodimerization encodes information at the molecular level and allows the predictable formation of discrete aggregates of nanometer dimensions. Evidence for the reversible assembly of these structures is provided by 1H NMR, guest encapsulation studies, and gel permeation chromatography. Covalent attachment of these calixarene aryl and sulfonyl ureas at their smaller (lower) rims leads to polymeric assemblies in which the informational content is preserved.