Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

摘要

Hydrogen bond-mediated self-assembly is a powerful strategyfor creating nanoscale structures. However, little is knownabout the fidelity of assembly processes that must occur when similarand potentially competing hydrogen-bonding motifs are present.Furthermore, there is a continuing need for new modules and strategiesthat can amplify the relatively weak strength of a hydrogen bond togive more stable assemblies. Herein we report quantitative complexationstudies on a ureidodeazapterin-based module revealing an unprecedentedstability for dimers of its self-complementaryacceptoracceptor-donor-donor (AADD) array. Linking two such unitstogether with a semirigid spacer that carries a first-, second-, orthird-generation Fréchet-type dendron affords a ditopic structureprogrammed to self assemble. The specific structure that is formeddepends both on the size of the dendron and the solvent, but all of theassemblies have exceptionally high stability. The largest discretenanoscale assembly is a hexamer with a molecular mass of about 17.8kDa. It is stabilized by 30 hydrogen bonds, including sixAADD⋅DDAA contacts. The hexamer forms and is indefinitely stablein the presence of a hexamer containing six ADD⋅DAAhydrogen-bonding arrays.