Comparative analysis of the conformations of symmetrically and asymmetrically deca- and undecasubstituted porphyrins bearing meso-alkyl or -aryl groups

X-ray crystallography and proton nuclear magnetic resonance spectroscopy were done to determine the structure of symmetrically and asymmetrically highly substituted porphyrins. The results showed that the decasubstituted free-base porphyrins with two meso-aryl substituents have a negligible out-of-plane distortion but a large amount of in-plane distortion, with the corresponding nickel(II) complexes having either planar or modestly nonplanar arrangements. The nickel(II) complexes of 5,15-diethyl-substituted porphyrins, on the other hand, were found to have very ruffled conformations, in spite of the planar arrangement of the corresponding free-base porphyrins.