Studies on the Conformation of 5,15-Diarylporphyrins with (Arylsulfonyl)oxy Substituents

Article abstract of DOI:10.1021/jo00257a013

Dimeso-substituted octaalkylporphyrins, carrying an (arylsulfonyl)oxy group at the ortho position of the two (meso) phenyl groups, were synthesized from dipyrrolylmethanes and aldehydes.On account of a 1H NMR upfield shift in CDCl3 solution of 2-5 ppm for the aryl protons, a folded conformation is assumed in which the substituted aryl groups lie right above and below the porphyrin plane.In CDCl3/CF3COOH solution the upfield shifts are absent.The results of low-temperature 1H NMR measurements and ring-current calculations agreed with our assumptions.The sulfonyloxy group promotes folding of the molecule more than the ester, sulfonyl, sulfinyl, thio, or methylene group.In zinc porphyrins carrying anthraquinone substituents, intramolecular coordination was observed. ΔG, ΔH, and ΔS values for the various conformational equilibria were calculated from the NMR data.We suggest van der Waals interactions with a contribution of charge transfer as the driving force for the folding of the molecule.