Thermoanalytical investigations about the metal–amino acid interactions

Abstract

The adducts CdCl 2 · 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 ·2Gly lost both ligands in a single step with an E a value of 113 kJ mol −1. CdCl 2 ·Gly prepared from water or 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.