THERMOCHEMISTRY OF SOME METALLIC AMINO-ACID COMPLEXES .1. COPPER(II) COMPLEXES

The standard (p(empty set) = 0.1 MPa) molar enthalpies of formation of the following crystalline copper(II) amino acid complexes were determined at 298.15 K by solution-reaction calorimetry: DELTA(f)H(m)empty set[Cu(gly)2, cr] = - 943.7 +/- 1.3 kJ mol-1; DELTA(f)H(m)empty set[Cu(ala)2, cr]= - 1003.7 +/- 1.5 kJ mol-1; DELTA(f)H(m)empty set[Cu(val)2, cr] = - 1124.1 +/- 2.2 kJ mol-1; DELTA(f)H(m)empty set[Cu(leu)2, cr] = - 1177.8 +/- 2.1 kJ mol-1; DELTA(f)H(m)empty set[Cu(isol)2, cr] = - 1156.3 +/- 1.8 kJ mol-1; DELTA(f)H(m)empty set[Cu(Phgly)2, cr] = - 772.3 +/- 1.9 kJ mol-1; DELTA(f)H(m)empty set[Cu(Phala)2, cr] = - 831.8 +/- 2.6 kJ mol-1. The results suggest a linear correlation between the standard molar enthalpies of formation of the crystalline copper(II) amino acid complexes and those of the corresponding crystalline amino acids. Estimations of the standard molar enthalpies of sublimation of the copper(II) amino acid complexes are presented. The total binding energy between the copper(II) and the amino acid ligand is derived and compared with the corresponding parameter for copper(II) acetylacetonate.