Physico-Chemical and Spectroscopic Investigations of New Metallic Complexes with Phenylalanine as Ligand

Abstract

The [Cu(L)2]⋅H2O (1), [Co(L)2]⋅2H2O (2) and [Zn(L)2]⋅H2O (3) metallic complexes with phenylalanine as ligand were synthesized in aqueous solution and characterized by means of atomic absorption, elemental analysis, differential scanning calorimetry, FT‐IR, UV‐VIS and ESR spectroscopies. The comparative analysis of the FT‐IR spectra for the ligand and the complexes indicate the coordination of the metallic centre to the carboxylic oxygen atom and to the nitrogen atom of the amino group. In the ligand spectrum the νs(N–H) stretching vibration appears splitted at 3078 cm−1 and 3030 cm−1 and is shifted at 3320 cm−1 and 3256 cm−1 in the copper complex, at 3220 cm−1 in the cobalt spectrum and at 3256 cm−1 and 3334 cm−1 for the zinc complex proving the involvement of the –NH2– group in the complex formation. The νs(C=O) stretching vibration emerge in the ligand spectrum at 1623 cm−1 and appears to be shifted toward higher wave numbers with 4 cm−1 and 10 cm−1 for Cu and Co complexes and with 9 cm−1 toward lower wave numbers for Zn complex. The n→π* characteristic band in the UV spectra assigned to the C=O bond appear at 231 nm for phenylalanine and is shifted toward lower wave lengths in the complexes spectra proving the covalent nature of the metal‐ligand bond. Powder ESR spectra at room temperature are typically for monomeric species with pseudotetrahedral symmetry around the copper ions and octahedral environment for the cobalt ion.