PORPHYRINS WITH 4 AZOLE SUBSTITUENTS IN MESO POSITIONS - X-RAY CRYSTAL-STRUCTURE OF MESO-TETRAKIS-(1-BENZYLPYRAZOL-4-YL)-PORPHYRIN AT 200-K

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-m ethoxybenzyl and SEM protected meso-pyrazolylporphyrins afforded the f irst known pyrazolylporphyrins with pyrazole free NH groups. The cryst al and molecular structure of meso-tetrakis-1-(benzyl-pyrazol-4-yl)por phyrin 4a has been solved by X-ray analysis. The porphyrin core displa ys a similar pattern of bond distances and angles to that of meso-tetr aphenylporphyrin itself. The pyrazole rings are almost perpendicular t o the macrocyclic ring in such a way that the nitrogen lone pairs of t he pyrazole N-2 atoms are situated, up, down, down, up, with regard to it (alpha alpha beta beta atropisomer).