LIPOPHILIC COORDINATION-COMPOUNDS - ALUMINUM, GALLIUM, AND INDIUM COMPLEXES OF 1-ARYL-3-HYDROXY-2-METHYL-4-PYRIDINONES

{A series of 1-aryl-3-hydroxy-2-methyl-4-pyridinones and tris(1-aryl-3-hydroxy-2-methyl-4-pyridinonato) aluminum(III), -gallium(III), and -indium(III) complexes have been prepared and completely characterized. The pyridinones have a variety of aryl substituents at the ring nitrogen atom (phenyl, p-tolyl, p-methoxyphenyl, p-nitrophenyl). The complexes have been studied by a number of techniques including n-octanol/water partitioning, potentiometry, and single-crystal X-ray diffraction. The uncomplexed ligands have log (n-octanol/water partition coefficients) (log p) greater than 1, except for the p-nitrophenyl case; the log p values are significantly higher in the complexes (> 2, except for the p-nitrophenyl cases). The complexes of 3-hydroxy-2-methyl-1-phenyl-4-pyridinone with aluminum (III), gallium (III), and indium (III) have been characterized by potentiometric (glass electrode) titration. The equilibria have been examined at 25.0 +/- 0.1-degrees-C (and 37.0 +/- 0.1-degrees-C for Al) at an ionic strength of mu- = 0.15. This ligand forms Ml(n) complexes (n = 1-3) of high stability; at 25-degrees-C the overall stability constants beta-3 for the 3:1 complexes are 10(30.7) (M = Al3+), 10(36.3) (Ga3+), and 10(31.1) (In3+). At ligand to metal ratios greater-than-or-equal-to 1, the ligands prevent M(III) hydrolysis at millimolar concentrations, even under slightly basic conditions, and the effective formation constants (beta-3eff) for the metal ions at physiological pH are 10(24.7) (M = Al3+), 10(30.3) (Ga3+), and 10(25.1) (In3+). Crystals of the ML3.5.5H2O complexes C39H36MN3O6.5.5H2O) (where M is Al or Ga, respectively, and L is the anion of 3-hydroxy-2-methyl-1-p-tolyl-4-pyridinone) are isomorphous and isostructural, crystallizing in the trigonal space group p3BAR1c with Z = 4