The ortho effect in ligation of iron tetraphenylporphyrins

The reactions of iron(II) tetramesitylporphyrin and iron(II) tetraphenylporphyrin with ligands in the sixth positions are elucidated. The binding kinetics and equilibria of isonitriles, 1-methylimidazole, 1, 2-dimethylimidazole and carbon dioxides to the iron porphyrins show the fifth and sixth ligand combinations which result in steric repulsion with the porphyrin group. The results also show a larger binding constant and lower dissociation rates for the tetramesitylporphyrins than the tetraphenylporphyrins.