Reversible Redox System of 2‐Oxypyritriphyrin(1.2.1) Accompanying Interconversion between 3‐Pyridone and 3‐Hydroxypyridine Units

To develop a π-conjugation circuit switched by redox reaction between 3-pyridone and 3-hydroxypyridine, ring-contracted analogue of oxypyriporphyrin, 2-oxypyritriphyrin(1.2.1) was prepared. When 2-oxypyritriphyrin treated with NaBH4, not only the 3-oxypyridine unit, but also meso-carbon reduced. The reduced analog could be oxidized again to afford in reversible manner.