Synthesis and characterization of Cu(II), Zn(II) and Fe(II) complexes supported by pyridylamide ligands

Abstract

Six new coordination complexes of Zn(II), Cu(II) and Fe(II) supported by pyridylamide ligands N-2-acetamidopyridine (Haap), N,N′-2,6-diacetamidopyridine (H2daap) and N,N′-2,6-pyridyl-bis[2,2,2-trifluoro-acetamide] (H2ptaa) were synthesized. The structures of the six complexes were characterized by X-ray crystallography, showing a N2O4 environment of the metal centers with octahedral geometries. Complexes 1 and 2 are mononuclear Zn(II) complexes supported by two Haap ligands or one H2daap ligand. The Cu(II) centers in complexes 3 and 4 showed a tetragonally elongated structure due to the John–Teller effect of the d9 electronic configuration of Cu(II). The two –CF3 groups on ligand H2ptaa led to the weaker interactions between the ligand and the Cu(II) center, which is supported by the X-ray crystal structure analysis and IR studies. For complexes 5 and 6, 1:1 and 2:1 ligand-to-metal ratios were observed in the mononuclear structures respectively. Evans’ method indicated both Fe(II) centers are high spin with four unpaired electrons in solution state. The theoretical studies of the complexes 1–6 included geometry optimization and IR vibrational frequencies calculation, which was compared with experimental spectra to assign the characteristic bands.