Manganese Phthalocyanine Coordination Chemistry: Recent Results and Present Status

A number of substituted manganese phthalocyanines (PcMn), which are easily soluble in organic solvents, have been synthesized with good yields (up to 76%) and high purity. PcMn with manganese +2 oxidation state without axial ligands was obtained for the first time and thoroughly characterized. It was shown that PcMn forms, PcMnIIIX, PcMnII or [LPcMnIII]2O, depending on substituents nature, can be stable in usual conditions. It was found that some PcMnII derivatives can be oxidized by water to PcMnIIIOH. The stages of substituted PcMn electrochemical reduction and oxidation have been studied and the correlation of redox potentials with electronic properties of substituents has been established. For the first time, the idea has been proposed and confirmed that PcMnII, when treated by organic bases in solution forms an equilibrium mixture of three electronic isomers — Pc+·MnI, PcMnII and Pc−·MnIII. A new scheme of PcMn photoreactions has been proposed and the possibility of using PcMn as a model of a photosystem component has been discussed. All the data are summarized in the complete scheme of photo and dark transformations between valence and coordination PcMn derivatives in solution.