Electrochemistry of Three-Dimensional Porphyrin Arrays and Related Compounds

Three-dimensional π-conjugated molecules have received extensive attention in many chemical research areas due to their interesting structure and unique characteristics. Among these situations, we found that oxidation of aromatic amines was useful for construction of distorted π-conjugated molecules under laboratory conditions. For example, oxidation of beta-amino substituted porphyrins provided three-dimensional porphyrins in excellent yield. In particular, sequential use of amination and oxidation toward 5,10,15,20-tetramesitylporphyrin effectively afforded highly twisted porphyrin oligomers. These oligomers exhibited high solubility in common organic solvent, which is promising for application to solution-processible molecular wire. In addition, we further investigated the substituent effect on the oxidation of beta-aminoporphyrins. We disclosed that dimerization products were varied dependent on meso-aryl substituents. In this presentation, we will show the electrochemical properties of these porphyrin oligomers in order to investigated the effect of distorted conformation on π-electronic network between porphyrin units. We also found oxidation of N-aryl beta-amino substituted porphyrins produced dehydropyrazine-bridged porphyrin dimers. Recently, we have succeeded in the synthesis of π-extended dihydrophenazine through oxidation of amino-substituted anthracenes. This molecule exhibited conformational change upon electrochemical and chemical redox conditions. Spectral analysis and theoretical calculation revealed that the aromatic and non-aromatic switch of the central dihydropyrazine moiety by two electron oxidation play important role for this electrochemical responsive behaviors. This time, we also prepared π-extended dihydrophenazine based on porphyrins. The structure was clearly elucidated by X-ray diffraction analysis, showing saddle-shape conformation. The electrochemical analysis exhibited irreversible characteristic upon one-electron oxidation and reduction as observed for anthracene derivatives. In this presentation, we will show the synthetic details and electrochemical behaviors of π-extended dihydrophenazines and related porphyrin arrays.