Cobalt(II) tetramethoxyphenylporphyrin (CoTMPP) is a metalloporphyrin complex where a cobalt ion is coordinated within the macrocyclic tetramethoxyphenylporphyrin ligand. This compound is characterized by its planar structure and strong absorption in the visible region, which is typical for porphyrin derivatives. Its primary application is in the field of materials science, particularly as a precursor or active component for oxygen reduction reaction (ORR) catalysts in fuel cells and metal-air batteries. The cobalt center in the porphyrin ring acts as the catalytic site, facilitating the multi-electron reduction of oxygen. Additionally, due to its extended π-conjugation and metal coordination, it is investigated as a functional material in organic electronics, such as in organic photovoltaics (OPV) and as a dye sensitizer. The compound is also utilized as a catalyst in various organic synthesis reactions, including oxidation and cyclization processes, leveraging the redox-active cobalt center. It is typically handled as a solid and requires storage under inert conditions due to potential sensitivity.