Complexation of Halogen-Substituted Tetraphenylporphyrins and Cadmium(II) Tetraphenylporphyrins with MnCl2 in DMF

The complexation of 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin and 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin and metal exchange reactions of their cadmium complexes with manganese(II) chloride in DMF were studied with the goal of finding optimal conditions for the synthesis of manganese(II) and manganese(III) complexes with tetrapyrrole macrocyclic compounds. ortho-Substituted manganese com­plexes were synthesized by prolonged heating of the corresponding porphyrins with excess MnCl2 in boiling DMF. Metal exchange reactions of cadmium(II) 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin and cadmium(II) 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin with MnCl2 in DMF produced the corresponding manganese(III) tetraphenylporphyrins. In contrast, the complexation of tetraphenylporphyrins substituted at both pyrrole and phenyl rings with manganese(II) chloride in DMF under mild conditions afforded manga­nese(II) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin, which was oxidized to a mixture of manganese(II) and manganese(III) porphyrins on exposure to air, and manganese(II) 2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin. The synthesized compounds were identified by electronic absorption spectroscopy, 1H NMR, and mass spectrometry. The metal exchange reactions of ortho-substituted cadmium(II) tetraphenylporphyrins and the complexation of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin with manganese(II) chloride in DMF were studied by spectrophotometry, and their kinetic and activation parameters were determined. A significant effect of β- and ortho-substitution on the complexation and metal exchange reactions was revealed.