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series of 3-hydroxy-2-methyl-4-pyridinones and their complexes with aluminum(III) have been characterized by potentiometric (glass electrode) titration. The equilibria have been examined at 25.0 ±0.1 °C and at ionic strengths of p = 0.15 and 0.6 M (NaCl). The pyridinones have a variety of substituents at the ring nitrogen atom (H, CH3, C2H5, and «-C6H13), and the pyridinonate anions are characterized by two stepwise protonation constants of ~109,8 and ~1037. These ligands form A1L" complexes (n = 1-3) of high stability; the overall stability constants ft for the 3:1 complexes are all >1030. At ligand to metal ratios >1, the ligands prevent Al(III) hydrolysis at millimolar concentrations, even under slightly basic conditions, and the effective formation constants (fttff) of the various ligands for Al3+ at physiological pH are 1024-1025. The binding of these ligands to Al34 is considerably enhanced (10 orders of magnitude) in comparison to that of their pyrone congeners. Two examples of the practical application of these data are discussed: (1) confirmation of Al34 speciation (particularly hydrolysis behavior) as deduced from 27A1 NMR spectra and (2) simulation of comparative metal binding in a simple blood plasma model.

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Can. J. Chem. 72, 1362 (1994.In model studies designed to study the synthesis of potentially hexadentate chelates based on the linkage of three furan rings to a triamine via amide linkages, new 2-and 4-substituted 3-hydroxy-5-methylfurans have been prepared. Particularly, 3-hydroxy-5-methyl-(N-methylforrnamido)furan (Hahm) and its Al and Ga complexes (M(ahm)3) have been prepared and thoroughly characterized by a variety of techniques, in the solid state and in solution. Solution equilibrium studies ( p = 0.6 M NaCl, 25°C) uncovered a complicated set of equilibria in the ~l~+ / H a h m system; the solution potentiometric data were best explained by the presence of mixed ligand (