Novel sitting-atop complexation between uranyl and meso-tetraarylporphyrins under mild conditions

We have investigated the effect of uranyl nitrate hexahydrate on free base meso-tetraarylporphyrins under mild conditions, at room temperature and containing a few drops of chloroform. The characterization of the products by 1H NMR, IR and UV–Vis spectroscopy, elemental analysis and electrical conductometry demonstrated sitting-atop complex structures. The sitting-atop complexes are metalloporphyrins in which the metal ion is bonded to fewer than four nitrogen atoms in the distorted porphyrin plane. Such complexes may be considered as models for the initial steps of metallation of the macrocycles. This attempt is the first report of the preparation of sitting-atop complexes for actinides.

Reaction of meso-tetraarylporphyrins with UO2(NO3)2 · 6H2O under mild conditions in a 1:1 mole ratio lead to the formation of sitting-atop complexes, in which two pyrrolenine nitrogen atoms in the porphyrin core act as electron donors to an uranium(VI) center and two protons on the pyrrole nitrogens still remain.Figure optionsDownload as PowerPoint slide