Spectroscopic studies of copper (II) complexes with some amino acids

Copper-amino acids complexes in aqueous solution: [Cu(L-1)(2)](H2O)-H-. (Li=lysine), [Cu(L-2)(2)](H2O)-H-. (L-2=glycine) and [Cu(L-3)(2)](H2O)-H-. (L-3= leucine) were synthesized and analyzed by means of elemental analysis, thermogravimetric analysis, atomic absorption, FTIR, UV-VIS and EPR spectroscopies. The thermogravimetric analysis results are similar for all the complexes, the mass losses occurred in one or more steps until the complexes were destroyed and the copper oxide was formed. The atomic absorption spectroscopy and elemental analysis confirms the compounds stoichiometry. The FTIR spectra show that amino acids act as bidentate ligands with the coordination involving the carbonyl oxygen and the nitrogen atom of amino group. Powder EPR spectra at room temperature are typical for monomeric species with square-planar local symmetry around the metal ion, the principal values of the g tensor are: g(parallel to)=2.180, g(perpendicular to)=2.100 for 1, g(parallel to)=2.205, g(perpendicular to)=2.090 for 2 and g(parallel to)=2.178, g(perpendicular to)=2.112 for 3. The EPR spectra of the Cu (II) - amino acids complexes in DMF solution display the copper hyperfine structure (g(0) approximate to 2.120, A(0) approximate to Pz 80 G).