Push-Pull Charge Transfer and High-Potentials Induced by Hypervalent Ions in Antimony(V) and Phosphorus(V) Porphyrins

Abstract

When main-group element phosphorus(V) or antimony(V) is inserted into the porphyrin cavity, the resulting phosphorus(V) porphyrin or antimony(V) porphyrin acquires several unique properties: (i) it remains as an excellent photosensitizer, (ii) introduces two chemically active axial bonds orthogonal to the plane of the porphyrin, (iii) attains strong oxidizing potentials, and (iv) induces a push-pull type intramolecular charge transfer. Our recent research has been focused on the latter two properties. The high oxidation number of the phosphorus and antimony ions makes the porphyrin central ring electron deficient. The presence of meso-substitutions (R) with moderate to high electron densities is sufficient to induce a push-pull type intramolecular electron transfer from peripheral aryl units to the central porphyrin ring. By varying the electron richness of the R unit, it is possible to modulate the charge transfer character. Steady-state and transient absorption studies were employed to establish the push-pull intramolecular charge transfer. Here, I will present some hypervalent porphyrins and discuss their structural, redox, and photophysical properties. Figure 1