Thermoanalytical investigations about the metal-amino acid interactions

摘要

The adducts CdCl_2 center dot xGly (x = 1, 2; Gly = glycine) were synthesized and characterized by IR spectroscopy, thermogravimetry (TG) and differential scanning calorimetry (DSC). The bisadduct was prepared in a water medium and the monoadducts 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 polarity of the medium on cation-amino acid interactions at pH values of about 7.0. CdCl_2 center dot 2Gly lost both ligands in a single step with an E_a value of 113 kJ mol~(-1). CdCl_2 center dot Gly prepared from water of a water-ethanol mixture lost the single ligand in two steps, whose activation energy values are 193; 134 and 88; 156 kJ mol~(-1), respectively.