Complexation of Molybdenum(VI) with Bis(3‐hydroxy‐4‐pyridinone)amino Acid Derivatives

Abstract

AbstractThe molybdenum(VI) binding properties of a series of 3‐hydroxy‐2‐methyl‐4‐pyridinones (3,4‐HP), namely bis(3,4‐HP)chelators, were investigated in solution and as solids; in particular, the complexation of MoVI with iminobis{acetyl[1‐(3′‐aminopropyl)‐3‐hydroxy‐2‐methyl‐4‐pyridinone]}, IDAPr(3,4‐HP)2, and ethylenediamino‐N,N′‐bis(methylcarboxyl)‐N,N′‐bis{acetyl[1‐(3′‐aminopropyl)‐3‐hydroxy‐2‐methyl‐4‐pyridinone]}, EDTAPr(3,4‐HP)2, as well as three model compounds: 1,2‐dimethyl‐3‐hydroxy‐4‐pyridinone (DFP), iminodiacetic acid (IDA), and ethylenediaminodiacetic acid (EDDA). Solution studies show that the complexation occurs at low pH values by the coordination modes of the hydroxypyridinone moiety, and with the formation of bischelated MoO22+ species. As the pH is increased, hydrolytic processes start with the formation of monochelated MoO3 complexes and is followed by the total recovery of the free ligand, at pH > 8 for most of the systems, but at pH 10 for EDTAPr(3,4‐HP)2. The obtained solid molybdenum complexes showed evidence for the presence of mononuclear species in solution, whereas the dinuclear species, (MoO2)2EDTAPr(3,4‐HP)2, were only detected for the EDTA derivative. Aqueous solution studies were performed by pH–potentiometry, spectrophotometry, 1H NMR and 17O NMR spectroscopy, and solid complex species were characterized by elemental analysis, IR spectroscopy, and ESI‐MS.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)