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The enthalpy change of the complexation reactions of the first-row transitional metal chlorides including CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with L--histidine in water were determined by a microcalorimeter at 298.15—323.15 K. The standard enthalpy of formation of 32Cr(His)+(aq) and 22M(His)+(aq) (M=Mn, Fe, Co, Ni and Cu) were calculated. Based on the thermodynamic and kinetic equations of the reactions, three thermody-namic parameters (the activation enthalpy, the activation entropy, the activation free energy), the rate constants, and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) are obtained. The solid complexes of CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with histidine were prepared and identified as Cr(His)2Cl3H2O, Mn(His)2Cl24H2O, Fe(His)2Cl2H2O, Co(His)2Cl2H2O, Ni(His)2Cl2H2O and Cu(His)2Cl2H2O by chemical and elemental analyses. The bonding characteristics of these complexes were char-acterized by IR as well. The results showed that, with the atomic number increasing, three thermodynamic parame-ters, GD!, HD! and SD! of the complexation reaction of these metal chlorides with L-a-histidine in water present an analogy regularity.
The enthalpy change of the complexation reactions of the first-row transitional metal chlorides including CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with L-histidine in water determined by a microcalorimeter at 298.15-323.15 K. The standard enthalpy of formation of 32Cr (His) + (aq) and 22M (His) + (aq) (M = Mn, Fe, Co, Ni and Cu) were calculated. Based on the thermodynamic and kinetic equations of the reactions, three thermodynamic parameters The activation enthalpy, the activation entropy, the activation free energy, the rate constants, and the three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) are obtained. The solid complexes of CrCl3, MnCl2, (His) 2Cl2H2O, Ni (His) 2Cl2H2O and Cu (His) 2Cl2H2O by FeCl2, CuCl2 and histidine were prepared and identified as Cr (His) 2Cl3H2O, chemical and elemental analyzes. The bonding characteristics of these complexes were char-acterized by IR as well. The results showed that, with the atomic number increasing, three thermodynamic parameters, GD !, HD! and SD! of the complexation reaction of these metal chlorides with L-a-histidine in water present an analogy regularity.