Appropriately substituted N-centered urazolyl radicals are capable of generating interesting cage-like structures upon forming N-N bonds. The radicals are generated by the oxidation of the corresponding NH urazole precursors. We synthesized a triurazole precursor that we hoped would dimerize through the formation of three N-N bonds to afford a large molecular cage. Unfortunately, the attempts at the oxidation of the urazoles to form urazolyl radicals instead only lead to random oligomerization, forming plastic-like materials rather than the desired cages.

Dynamic covalent chemistry (DCvC) is a powerful means by which to rapidly prepare complex structures from simple molecular building blocks. Effective DCvC behavior is contingent upon the reversibility of covalent bond formation. Stabilized radical species, therefore, have been effectively used for these applications. In earlier work we demonstrated that properly substituted 1-arylurazolyl radicals showed promise as oxygen-insensitive heterocyclic N-centered radicals with a propensity for reversible bond formation. In this work we have synthesized several tethered bis(urazolyl) diradicals, varying by the type and length of connectivity between the urazole rings, and tested them for DCvC behavior. We have found that when the two aryl rings to which the urazolyl radical sites are attached are tethered by a chain of five or more carbons, equilibrium mixtures of monomeric and dimeric species are formed by N− N bond formation between two radical sites. DCvC behavior is observed that is sensitive to changes in temperature, concentration, and (to a lesser extent) solvent. In general, the dimer species is favored at lower temperatures and higher concentrations.