Self-assembled pentamers and hexamers linked through quadruple-hydrogen-bonded 2-ureido-4[1H]-pyrimidinones
H. M. Keizer, J. J. González, M. Segura, P. Prados, R. P. Sijbesma, E. W. Meijer, J. de Mendoza
Chem. Eur. J. 2005, 11, 4602-4608
Abstract: The preorganization of bifunctional 2-ureido-4-pyrimidinones mediated by either 1,3-substituted adamantane or meta-substituted phenylene ring linkers leads to the preferred formation of stable pentameric (1)5 and hexameric (2)6 assemblies, respectively. Despite the high binding constant of the 2-ureido-4-pyrimidinone dimers and the highly preorganized structure of the monomer, the predominant formation of cycles (1)5 and (2)6 in solution occurs only within a specific concentration range.