Spontaneous nucleophilic addition of hydroxide ions to the meso-position of high-valent antimony-oxo porphyrin complexes.
Bimolecular reactions of the antimony(V) porphyrin complexes SbO(tpp)OH, 1 and SbO(oep)OH, 2 with tetra-n-butylammonium hydroxide were investigated at 298 K in acetonitrile solution (tpp, dianion of 5,10,15,20-tetraphenylporphyrin and oep, dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin). Spontaneous nucleophilic addition of hydroxide ions to the non-oxidized porphyrin macrocycle leads to novel hydroxyphlorin derivatives, which contain a saturated meso-carbon bridge. While this process is a reversible equilibrium reaction for the TPP derivative, the OEP complex undergoes subsequent demetallation and oxidative ring cleavage in the presence of dioxygen. Possible implications for the competitive inhibition of heme-oxygenase by high-valent metalloporphyrin therapeutics are discussed.
Knör
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University Regensburg, Institut für Anorganische Chemie, Regensburg, Germany. guenther.knoer@chemie.uni-regensburg.de
D000818:Animals; D000965:Antimony; D004791:Enzyme Inhibitors / Q000737:chemistry; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors; D006801:Humans; D006878:Hydroxides / Q000378:metabolism*; D006900:Hydroxylation; D008665:Metalloporphyrins / Q000737:chemistry*; D015394:Molecular Structure; D013057:Spectrum Analysis
D004791:Enzyme Inhibitors; D006878:Hydroxides; D008665:Metalloporphyrins; D006418:Heme; C031356:hydroxide ion; D000965:Antimony; D006419:Heme Oxygenase (Decyclizing)