Molecular structure of simple mono- and diphenyl meso-substituted porphyrin diacids: influence of protonation and substitution on the distorsion

The crystal and molecular structures of three simple porphyrin diacids have been determined from X-ray diffraction data to delineate how the peripheral substituents of the porphyrin affect the overall molecular flexibility. Di-meso-substituted [DPPH4]2+(CF3CO2−)2 and, mono-meso-substituted [MPPH4]2+(CF3CO2−)2 and [dedmMPPH4]2+(CF3CO2−)2 porphyrin diacids show increasingly saddled core conformation. Some of the spectroscopic properties (NMR and UV–visible) of the porphyrin diacids are also discussed in terms of the observed structures.