Efficient Synthesis of Arylenedioxy‐Bridged Porphyrin Dimers through Catalyst‐Free Nucleophilic Aromatic Substitution

A series of porphyrin dimers bridged by one or two rigid arylenedioxy linkers was successfully synthesized by catalyst‐free meso‐aryloxylation involving nucleophilic aromatic substitution. The orientational freedom and conformation of the two porphyrin macrocycles in the mono‐bridged dimers depended on the steric hindrance between the macrocycles and substituents on the arylenedioxy linkers. On the other hand, the bis‐bridged dimers exhibited a highly rigid cofacial conformation with a distinct interplanar distance. The fluorescence quantum yields of the bis‐bridged dimers (Φfl=0.094 and 0.096) were quite similar to those of the monomers (Φfl=0.13). Owing to their high rigidities, the nonradiative deactivation of the photoexcited states associated with dimerization, which are observed for reported dimers, are mostly suppressed, thus suggesting that those dimers have highest rigidities among the cofacial porphyrin dimers exploring emission properties. Cyclic voltammetry revealed the electronic communication between the porphyrin macrocycles in the closely stacked bis‐bridged dimer. Rigid bridges: A series of porphyrin dimers bridged by one or two arylenedioxy linkers was successfully synthesized in high yields by catalyst‐free nucleophilic aromatic substitution. The orientational freedom and conformation of the two porphyrin macrocycles in the mono‐bridged dimers were controlled by the substituents on the arylenedioxy linkers. Bis‐bridged dimers exhibited a highly rigid cofacial conformation.