meso‐Diazacorrphycenes: Neighboring Effect of Two Nitrogen Atoms

The neighboring effect of two adjacent heteroatoms influences the structures and properties of heterocyclic compounds. Herein, we demonstrated that the introduction of two adjacent sp2 nitrogen atoms into a porphyrinic skeleton significantly enhanced its Brønsted basicity due to the repulsive interaction between two lone pairs on the nitrogen atoms. Palladium‐ and copper‐templated ring closure of dichlorobis(dipyrrin) with hydrazine hydrate provided meso‐diazacorrphycene palladium and copper complexes in good yields. The structural, magnetic, and electrochemical properties of the diazacorrphycene complexes were investigated experimentally and theoretically to elucidate the effect of the meso‐nitrogen atoms. PdII and CuII meso‐diazacorrphycenes have been efficiently prepared via cyclization of dichlorobis(dipyrrin) with hydrazine hydrate by the metal template strategy. Electrochemical analysis revealed their electron‐deficient nature owing to the electron‐withdrawing diazo moiety. Titration experiments with trifluoroacetic acid demonstrated the higher Brønsted basicity of PdII diazacorrphycene than that of PdII diazaporphyrin because of the interaction between two lone pairs on the nitrogen atoms (see figure).