Iron(III) and cobalt(III) complexes with pentadentate pyridoxal Schiff base ligand – structure, spectral, electrochemical, magnetic properties and DFT calculations

• Published in: Polyhedron 2021-03, Vol.197, p.115019, Article 115019
• Main Authors: Murašková, Viera, Eigner, Václav, Dušek, Michal, Sedmidubský, David
• Format: Article
• Language: English
• Subjects: Cobalt(III) complex; Crystal structure; Cyclic voltammetry; DFT calculations; Iron(III) complex; Magnetic properties; Pentadentate Schiff base; Pyridoxal
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2021.115019

Iron(III) and cobalt(III) complexes with pyridoxal Schiff-base ligand are prepared. These compounds are characterized by single-crystal XRD. Magnetic properties of the iron(III) complex are discussed in terms of spin Hamiltonian involving ZFS term. The electronic structure calculations are performed using DFT. Redox properties of the compounds are investigated by CV. [Display omitted] •Iron(III) and cobalt(III) complexes with pyridoxal Schiff base were prepared.•The complexes were characterized by single-crystal X-ray structure analysis.•The magnetic data were analysed using the spin Hamiltonian including the ZFS term.•The electronic structure calculations were performed using DFT.•Redox potentials of the ligand and complexes were investigated by CV. Three complexes, [FeLCl]Cl·H2O, [Co2L2H3O2]Cl·4.8H2O, and [CoLN3], where L2– is the dianion of an asymmetric propyl-ethyl pentadentate Schiff base ligand condensed from pyridoxal and N-(2-aminoethyl)propane-1,3-diamine, have been synthesized and characterized by elemental analysis, FT-IR and mass spectroscopy. Crystal structures of the complexes along with the Schiff base were determined by X-ray diffraction. 1HNMR spectrum of the Schiff base has been obtained. The coordination polyhedra of all three complexes can be expressed as distorted octahedra. Magnetic investigations of [FeLCl]Cl·H2O complex confirmed high-spin state over the whole temperature range (5–300 K) and allowed the evaluation of the axial zero-field splitting (ZFS) parameter D = –0.97 cm−1, intermolecular exchange parameter zj́ = –0.88 cm−1 and temperature-independent paramagnetism χTIM = 0.00025 cm3mol−1. The low-spin state of Co(III) was stabilized in diamagnetic [Co2L2H3O2]Cl·4.8H2O and [CoLN3] complexes. Redox potentials of the Schiff base and the complexes were investigated by cycling voltammetry on the GC electrode in dry acetonitrile. The experimental magnetic properties of the complexes [FeLCl]Cl·H2O and [CoLN3] were compared with the theoretical ones calculated using density functional theory (DFT).