Enhancement of phlorin stability by the incorporation of meso-mesityl substituents

The effect of sterically bulky mesityl substituents on the stability of meso-substituted phlorins was examined. Three different phlorins bearing zero, two or three mesityl substituents were prepared via alkylation of the appropriate porphyrins. The stability of each phlorin was examined by UV–vis spectral monitoring of dilute solutions exposed to ambient light and air. UV–vis and mass spectral analyses performed after decomposition revealed qualitative differences in the degradation products. This study shows that the selection and positioning of peripheral substituents can enhance phlorin stability.