Melamine–Barbiturate Supramolecular Assembly as a pH‐Dependent Organic Radical Trap Material

In the last two decades, a large number of self‐assembled materials were synthesized and they have already found their way into large‐scale industry and science. Hydrogen‐bond‐based supramolecular adducts are found to have unique properties and to be perfect host structures for trapping target molecules or ions. Such chemical systems are believed to resemble living matter and can substitute a living cell in a number of cases. Herein, a report on an organic material based on supramolecular assembly of barbituric acid and melamine is presented. Surprisingly, the structure is found to host and stabilize radicals under mild conditions allowing its use for biological applications. The number of free radicals is found to be easily tuned by changing the pH of the environment and it increases when exposed to light up to a saturation level. We describe a preparation method as well as stability properties of melamine–barbiturate self‐assembly, potentiometric titration, and hydrogen ions adsorption data and EPR spectra concerning the composite. A surprising property of melamine–barbiturate (M–BA) composite is shown here as a radical trap, the capacity of which greatly depends on pH. It is suggested that the layered structure of the M–BA composite may be the host for trapped oxygen molecules, which in turn react with a short‐lived barbiturate radical and stabilize in the interlayer space.