Synthetic, spectroscopic, magnetic, and X-ray structural studies on a vitamin B₆-amino acid Schiff base complex, aqua(5'-phosphopyridoxylidenetyrosinato)copper(II) tetrahydrate

Abstract

A Schiff base metal complex, [Cu^II(PLP-DL-tyrosinato)(H₂O)].4H₂O (PLP = pyridoxal phosphate), with the molecular formula CuC₁₇O₁₃N₂H₂₇P has been prepared and characterized by magnetic, spectral, and X-ray structural studies. The compound crystallizes in the triclinic space group P1̅ with a = 8.616 (2) Å, b = 11.843 (3) Å, c = 12.177 (3) Å, α = 103.40 (2)°, β = 112.32 (2)°, γ = 76.50 (1)°, and Z = 2. The structure was solved by the heavy-atom method and refined by least-squares techniques to a final R value of 0.057 for 3132 independent reflections. The coordination geometry around Cu^II is distorted square pyramidal with phenolic oxygen, imino nitrogen, and carboxylate oxygen from the Schiff base ligand and water oxygen as basal donor atoms. The axial site is occupied by a phosphate oxygen from a neighboring molecule, thus resulting in a one-dimensional polymer. The structure reveals π-π interaction of the aromatic side chain of the amino acid with the pyridoxal π system. A comparative study is made of this complex with similar Schiff base complexes. The variable-temperature magnetic behavior of this compound shows a weak antiferromagnetic interaction.