Spectrophotometric Study of Palladium(II) Complexation with Elementary Amino Acids in Aqueous Solution

Complex formation of aqua palladium(II) ions with glycine (Gly), beta-alanine (beta-Ala), and taurine (Tau) in aqueous solution was studied by spectrophotometric titration at I = 1.0 mol/L (HClO4 + NaClO4) and T = 25 +/- 1 degrees C. A monoligand complex appeared at pH 0 in the H-Pd-Gly system under the conditions of our experiment; mono- and biscomplexes were formed at pH 1. In the H-Pd-beta-Ala system, a monoligand complex was formed at pH 1 and mono- and biscomplexes were formed at pH 2. In the H-Pd-Tau system, a monoligand complex was formed at pH 1 and 2. Molar absorption coefficients were calculated: the peak absorption occurs at lambda = 370 nm and epsilon = 203 L/(mol cm) for the monoligand glycinate complex [PdGly(H2O)(2)](+); at lambda = 325 nm and epsilon = 274 L/(mol cm) for the biscomplex [PdGly(2)](0); at lambda = 365 nm and epsilon = 342 and 297 L/(mol cm) for the beta-alaninate [Pd beta-Ala(H2O)(2)]+ and taurinate [PdTau(H2O)(2)](+) monoligand complexes, respectively; and at lambda = 330 nm and epsilon = 549 L/(mol cm) for the beta-alaninate biscomplex [Pd beta-Ala(2)](0). Logarithmic concentration formation constants were calculated for glycinate (log beta(1) = 15.03 +/- 0.07, and log beta(2) = 28.97 +/- 0.28), beta-alaninate (log beta(1) = 13.94 +/- 0.05, and log beta(2) = 25.24 +/- 0.06), and taurinate (log beta 1 = 9.74 +/- 0.08) palladium(II) complexes.