X-ray and NMR structural studies of the series of porphyrazines with peripheral pyrrolyl groups

Abstract Magnesium(II) and metal-free porphyrazines containing peripheral 2-methyl-5-phenyl- or 2,3,5-triphenyl-1 H -pyrrol-1-yl substituents were synthesized and subjected to physicochemical characterization, including high-resolution mass spectrometry, nuclear magnetic resonance, HPLC purity analysis, and UV-Vis spectroscopy, accompanied by the aggregation study in dichloromethane and pyridine. Single crystals of magnesium(II) porphyrazines were subjected to X-ray structure analysis. The presence of atropisomers of magnesium(II) porphyrazines with peripheral 2-methyl-5-phenyl- or 2,3,5-triphenyl-1 H -pyrrol-1-yl substituents was noticed in the NMR study and was confirmed by crystal structure determination. The NMR and X-ray data provided the evidence for the hindered rotation of the asymmetrical peripheral pyrrolyl substituents in magnesium(II) porphyrazines which resulted in obtaining compounds composed of different types of atropisomers, other than α 4 , preferentially α 3 β and αβαβ.