Porphyrins with four azole substituents in meso positions: X-ray crystal structure of Meso-tetrakis-(1-benzylpyrazol-4-yl)-porphyrin at 200 K

Abstract

Several new porphyrins have been prepared in improved yields using an established method which was adapted to formylpyrazoles bearing on the pyrazole N 1-nitrogen protective groups. The deprotection of N-para-methoxybenzyl and SEM protected meso-pyrazolylporphyrins afforded the first known pyrazolylporphyrins with pyrazole free N H groups. The crystal and molecular structure of meso-tetrakis-1-(benzyl-pyrazol-4-yl)porphyrin 4a has been solved by X-ray analysis. The porphyrin core displays a similar pattern of bond distances and angles to that of meso-tetraphenylporphyrin itself. The pyrazole rings are almost perpendicular to the macrocyclic ring in such a way that the nitrogen lone pairs of the pyrazole N 2 atoms are situated, up, down, down, up, with regard to it (ααββ atropisomer).