| Calcium-43 nuclear magnetic resonance (NMR) behavior of a number of calcium salts was studied in acetone, dimethylsulfoxide, dimethylformamide (DMF), ethylene glycol, formamide, methanol, propylene carbonate, tetramethylguanidine, and water as a function of salt concentration. There was evidence for ion-pairing for the chlorides, bromides, perchlorates, and nitrates in all solvents except DMF. The complexation of Ca('2+) ion with ethylenediaminetetraacetic acid (EDTA), and crown ethers 18-crown-6 (18C6) and 15-crown-5 (15C5) was also studied. The complexes with EDTA and 18C6 exhibited a slow exchange of the ('43)Ca ion between the free and complexed state, resulting in two resonances. There was no evidence for Ca('2+) ion complexation with 15C5.; The tetraphenylarsonium (and tetraphenylphosphonium) tetraphenylborate single ion assumption was studied using ('75)As, ('31)P, ('11)B, ('13)C, and proton NMR. Due to broad resonance lines (1000 Hz), ('75)As NMR was not sufficiently precise to test the validity of the assumption. Phosphorous-31 and boron-11 NMR data show that the central ion is not entirely shielded from the solvent, although ion-ion interactions are negligible. Carbon-13 data indicate that the charge is not localized on the central atom. Both carbon-13 and proton data indicate that tetraphenylarsonium, tetraphenylphosphonium, and tetraphenylborate ion are not solvated equivalently. Ion-ion interactions, as seen by ('13)C and proton NMR, are negligible. Care is advised when using this assumption to calculate free energies of transfer for single ions.; Complexation of phosphonoacetic acid (PAA) with calcium ion was studied potentiometrically in aqueous solution. The thermodynamic formation constants for the deprotonated and monoprotonated PAA complexes with Ca('2+) were found to be: log K(,f) = 4.68 (+OR-) 0.03 and log K(,f) = 2.68 (+OR-) 0.08, respectively. The thermodynamic quantities; (DELTA)G(DEGREES) = -6.38 0.07 kcal/mole; (DELTA)H(DEGREES) = 0.6 0.2 kcal/mole; (DELTA)S(DEGREES) = 21.4 0.7 cal/(DEGREES)K-mole; were calculated from the temperature dependence of the formation constant for the deprotonated PAA complex with Ca('2+) ion. The formation constant of manganese(II) ion with PAA was determined using electron spin resonance, while the complexation constants of copper(II), lead(II), and thallium(I) with PAA were determined using cyclic voltammetry. The silver(I) ion complexation constant with PAA was measured potentiometrically. The complexation of calcium(II), manganese(II), and thallium(I) ion was studied with the ligands 3-phosphonopropionic acid and phosphonoformic acid, resulting in the determination of formation constants for these ligands. |
