N-Substituted Dicyanomethylphenyl Radicals: Dynamic Covalent Properties and Formation of Stimuli-Responsive Cyclophanes by Self-Assembly

Dynamic covalent bonds and their chemistry have been of particular interest both from a fundamental and materials science aspect. Demonstrated herein is that triphenylamine (TPA) and carbazole (Cz), substituted with a dicyanomethyl radical, are useful motifs for dynamic covalent chemistry as they have the appropriate bond strength between monomer units as well as high stability and synthetic simplicity. TPA and Cz units substituted by two dicyanomethyl radicals formed macrocyclic oligomers classified as novel types of azacyclophanes, and in particular, the TPA‐based diradical gave a cyclic dimer in almost quantitative yield. The cyclic oligomers exhibited thermo‐ and mechanochromic behavior resulting from the generation of radical species by intermonomer C−C bond cleavage. Back and forth: Triphenylamine (TPA) and carbazole (Cy) derivatives substituted with a dicyanomethyl radical were found to be useful building blocks in dynamic covalent chemistry because of the reversible association/dissociation reaction between radicals. The bond dissociation energy of the intermonomer bond can be tuned by appropriate substituents. The TPA‐ and Cz‐based diradical analogues formed cyclic oligomers with defined sizes.