The photocatalytic decompositions of 1,2-diols by newly synthesized [meso-tetrakis(3,5-dichloro-1-methyl-4-pyridiniumyl)porphyrinato]iron(III) Fe(III)TCl2MPyP were compared with those by [meso-tetrakis(1-methyl-4-pyridiniumyl)prophyrinato]iron(III) Fe(III)TMPyP. Cofacially hindered FeTCl2MPyP was more robust and substrate-specific than FeTMPyP.