Probing the Dynamic Covalent Chemistry Behavior of Nitrogen-Centered Di- and Triurazole Radicals

Dynamic
covalent chemistry (DCvC) describes systems in which readily
reversible bond formation allows for control of product distributions
by straightforward manipulation of reaction conditions (e.g., changes
in temperature, solvent, concentration, etc). Nitrogen-centered 1-aryl
urazole radicals reversibly form tetrazane dimers in solution via
N–N bond formation. When two such urazole units are attached
to a single, appropriately substituted benzene ring, the resulting
diradical system engages in DCvC. At room temperature, a polymeric
network of units is created that exhibits gel-like properties, while
at higher temperatures, near quantitative dimerization to form a molecular
cage is observed.However, attaching three such urazole units to a
single appropriately substituted benzene ring inhibits DCvC behavior.