The photochemical and photocatalytic properties of iron meso-tetraarylporphyrins bearing an OH- axial ligand and different substituents in the beta-positions of the porphyrin ring are reported. Irradiation (lambda = 365 nm) in the absence of dioxygen leads to the reduction of Fe-III to Fe-II with the formation of OH* radicals. Substituents at the pyrrole P-positions are found to markedly affect the photoreduction quantum yields. Under aerobic conditions, this photoreaction can induce the subsequent oxidation of cyclohexane to cyclohexanone and cyclohexanol by O-2 itself. The process occurs under mild conditions (22 degrees C; 760 Torr of Or) and without the consumption of a reducing agent. The polarity of the solvent and the nature of the porphyrin ring have a remarkable effect on the selectivity of the photooxidation process, likely controlling the cleavage of O-O bonds of possible iron peroxoalkyl intermediates. In particular, in pure cyclohexane, oxidation occurs with the selective formation of cyclohexanone; in contrast, in dichloromethane/cyclohexane mixed solvent, the main oxidation product is cyclohexanol. Phenyl-tert-butylnitrone (pbn) has been found to quench the radical chain autooxidation of the substrate thus increasing the yield of cyclohexanol. This becomes the only oxidation product when iron 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin hydroxide (Fe-III(TDCPP)(OH)) is used as photocatalyst.