Syntheses and structure investigations of 3d transition metal complexes with a flexible N₄O₂-donor hexadentate Schiff-base ligand

The syntheses and structure investigations of four new 3d transition metal complexes (1-4) with a flexible N4O2-donor hexadentate Schiff-base ligand are described; three complexes (1, 2, and 4) of Fe^III, Co^III, and Cu^II metal ions have been investigated by UV-vis, FT-IR, high-resolution mass spectrometry (HR-MS), and scanning electron microscopy-electron dispersive spectroscopy, as well as single crystal X-ray diffraction. The X-ray structure of Ni^II complex 3 is also reported. The molecular structures of the complexes (1-3) demonstrate distorted octahedral coordination geometry, each exhibiting 1:1 (M:L) ratios and the Cu^II complex 4 shows a trinuclear structure with a Cu^II:L ratio of 3:2 in the solid state, which has been proven by X-ray diffraction. On the other hand, a mononuclear species of the Cu^II complex is formed in solution, which has been identified by electrospray ionization HR-MS.