Spectroscopic studies of copper (II) complexes with some amino acid as ligand
Pages 77-85
Maria Hübner, I. Hauer, Csilla Muller, D. Rusu, Klara Botond, L. David
Abstract
Cooper-amino acids complexes: [Cu(L1)2]•H2O (1), L1 – hystidine; [Cu(L2)2]•H2O (2), L2 – methionine and [Cu(L3)2]•H2O (3), L3 – threonine have been synthesized and characterized by means elemental analysis, FT–IR, UV–VIS and ESR spectroscopies.
The atomic elemental measurements confirm the 1:2 metal ions: amino acid ratio composition for the synthesized compounds.
Through FT-IR spectroscopy were obtained information about the copper (II) ions coordination. In the FT-IR spectra of the ligand the νs(N–H) stretching vibration appears at 3082 cm-1 (L1), 3146 cm-1 (L2) and 3176 cm-1 (L3) and is shifted in the spectra of the complexes (49 cm-1, 83 cm-1, 35 cm-1 respectively) proving the involvement of the –NH2– group in the complex formation. The ν(C=O) stretching vibrations is shifted in the complexes spectra confirming the involvement of the carboxylic group in the metal ions covalent bonding.
The local symmetry of the copper ions was obtained by comparing the ligand UV-VIS spectra with those of amino acid complexes.
The powder EPR spectra of the complex (1) measured at room temperature is characterized by the presence of an isotropic signal centred at g= 2.094, which can be assigned to an Oh symmetry around the copper ion. Powder ESR spectrum of (2) is typical for monomeric species with square-planar local symmetry around the metal ion (gII = 2.197, g = 2.136). Powder ESR spectrum of the complex (3) correspond to the monomeric pseudotetrahedral species with a CuN2O2 local cromophore.