ALUMINUM CARBOXYLATES IN AQUEOUS-SOLUTIONS .3. SYNTHESIS AND SOLUTION-STATE OF [AL2(CIT)2(H2O)6], [AL2(TART)3(H2O)4] AND [AL(GLUC)(OH)2] (H3CIT = CITRIC-ACID, H2TART = TARTARIC ACID, HGLUC = GLUCONIC ACID)

The complexes [Al2(cit)2(H2O)6] and [Al2(tart)3(H2O)4] (H-3cit = citri c acid, H-2tart = tartaric acid) have been prepared by controlled addi tion of the relevant alpha-hydroxycarboxylic acids to Al(OH), while [A l(gluc)(OH)2] (Hgluc = gluconic acid) was obtained by stoichiometric a ddition of potassium gluconate to a solution of [Al(H2O)6]3+. The solu tion state of these complexes was investigated by means of combined IR and H-1 NMR spectroscopies in D2O, at room temperature. In all cases, solutions were analysed at autogenous (2.5-4.0) and at physiological pH values, with the aim of checking the agreement between the solution state as predicted from available thermodynamic data and the real, to xicologically relevant, state stemming from spectroscopic observations . The Al(III)-citrate system is found to behave according to the therm odynamic expectations down to millimolar metal concentrations. On the contrary, the tartrate and gluconate systems do not agree with thermod ynamic predictions, albeit differently, at 0.1 and 0.3 mol dm-3 analyt ical concentrations.