Phosphate-triggered self-assembly of N-[(Uracil-5-yl)methyl]urea: a minimalistic urea-derived hydrogelator

N-[(Uracil-5-yl)methyl]urea is reported as a minimalistic low-molecular-weight hydrogelator (LMWHG). The unusual phosphate-induced assembly of this compound has been thoroughly investigated by IR, UV/Vis, and NMR spectroscopy, electron microscopy, and rheological experiments. This rare example of an anion-triggered urea-based LMWHG is the first example of a pyrimidine- and urea-containing molecule that can be forced into self-assembly in aqueous solution without additional aromatic or lipophilic groups. The gelator/phosphate ratio within the hydrogel was successfully determined by (31) P MAS NMR spectroscopy. The hydrogel exhibits a very fast and repeatable self-healing property, and remarkable G' values. The viscoelastic properties of the hydrogel can easily be tuned by variation of the phosphate ratio.