Design, Synthesis and Aggregation of Amphiphilic Monomers-Cyclic and Tubular Hydrogen-Bonded Self-assembly in...

Two hydrogen-bonding monomers containing tetraethylene glycol (TEG) chains have been synthesized and characterized. The monomers are based on a bicyclic scaffold appended with either 4H-bonding benzyl-substituted ureidopyrimidinone motifs or 2H-bonding unsubstituted pyrrole-fused ureidopyrimidinone motifs, with the TEG chains introduced with the aim of developing amphiphilic monomers soluble in nonpolar and polar organic solvents in order to extend the utility of H-bonding in supramolecular chemistry. In CDCl₃, both monomers formed cyclic tetramers. The monomer containing 2H-bonding motifs was found to form significantly less-stable aggregates than its previously reported alkylated analogue, most likely due to interference from the TEG chains. Despite the weaker aggregation, the 2H-bonded tetramers were able to stack into tubular polymers through orthogonal H-bonding in less polar solvent (toluene) or when a suitable guest (C₇₀) was introduced. Comparison of the TEGylated monomers with previously reported alkylated analogues showed that the introduction of TEG chains resulted in increased solubility in a wide range of solvents. By using one of the TEGylated monomers, nonpolar C₆₀ could be solubilized in polar solvent acetonitrile by forming an inclusion complex. This complex was used as a homogeneous catalyst for photochemical oxidation of sulfides to sulfoxides in acetonitrile.