Thermoanalytical investigations about the metal-amino acid interactions

The adducts CdCl2.xGly (x = 1, 2; Gly = glycine) were synthesized and chara cterized by IR spectroscopy, thermogravimetry (TG) and differential scannin g calorimetry (DSC). The bisadduct was prepared in a water medium and the m onoadducts were isolated with water or water-ethanol mixtures as solvents. IR, TG and DSC data obtained showed that metal-amino acid interactions can be strongly influenced by the total amount of amino acid present. By using TG data, the kinetic parameters, activation energy (E-a), frequency factor (A) and order of reaction (n), were calculated. E-a values can provide very important information about the influences of the stoichiometry and polari ty of the medium on cation-amino acid interactions at pH values of about 7. 0. CdCl2 . 2Gly lost both ligands in a single step with an E-a value of 113 kJ mol(-1). CdCl2 . Gly prepared from water or a water-ethanol mixture los t the single ligand in two steps, whose activation energy values are 193; 1 34 and 88; 156 kJ mol(-1), respectively. (C) 1999 Elsevier Science Inc. All rights reserved.