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<p>Dinuclear and mononuclear pyridoxal Schiff base complexes, specifically [{FeL}<sub>2</sub>(<i>µ</i>-O)]·2.2H<sub>2</sub>O (<b>1</b>) and [NiL’(H<sub>2</sub>O)]·2H<sub>2</sub>O (<b>2</b>) (where L<sup>2–</sup> is the dianion of tetradentate pyridoxal Schiff base generated in situ by the iron-catalyzed oxidative C − N bond cleavage of the initial pentadentate Schiff base, and L’<sup>2–</sup> is the dianion of pentadentate Schiff base ligand formed from pyridoxal and <i>N</i>-(2-aminoethyl)propane-1,3-diamine) have been synthesized and characterized by elemental analysis, Fourier transform infrared spectroscopy, and mass spectrometry. The crystal structures of these complexes were determined using single-crystal X-ray diffraction. The Fe atoms in complex <b>1</b> exhibit a distorted square pyramidal coordination geometry, while Ni atom in complex <b>2</b> displays a distorted octahedral geometry. The most significant finding is the strong antiferromagnetic exchange coupling observed in the diiron complex <b>1</b>. Magnetic susceptibility data revealed an exchange coupling constant of <i>J</i> = − 173&#xa0;cm<sup>–1</sup>, confirming its potential role as a model for non-heme diiron metalloenzymes. In contrast, complex <b>2</b> exhibits typical paramagnetic behavior of an octahedral Ni(II) complex with two unpaired electrons. Calculations based on density functional theory confirmed the high-spin state of the Fe(III) centers in the diiron complex and verified the magnitude of the strong antiferromagnetic exchange coupling. For the nickel complex, these calculations also revealed a significant degree of bond covalency, providing a comprehensive understanding of the structural and magnetic properties of these pyridoxal-based coordination compounds.</p>

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Strong antiferromagnetic interaction in µ-Oxo-bridged diiron(III) complex and paramagnetic nickel(II) complex of pyridoxal Schiff base ligands

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  • 发表日期：

    2026年2月18日

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  • Viera Murašková,
  • Václav Eigner,
  • David Sedmidubský

摘要

Dinuclear and mononuclear pyridoxal Schiff base complexes, specifically [{FeL}2(µ-O)]·2.2H2O (1) and [NiL’(H2O)]·2H2O (2) (where L2– is the dianion of tetradentate pyridoxal Schiff base generated in situ by the iron-catalyzed oxidative C − N bond cleavage of the initial pentadentate Schiff base, and L’2– is the dianion of pentadentate Schiff base ligand formed from pyridoxal and N-(2-aminoethyl)propane-1,3-diamine) have been synthesized and characterized by elemental analysis, Fourier transform infrared spectroscopy, and mass spectrometry. The crystal structures of these complexes were determined using single-crystal X-ray diffraction. The Fe atoms in complex 1 exhibit a distorted square pyramidal coordination geometry, while Ni atom in complex 2 displays a distorted octahedral geometry. The most significant finding is the strong antiferromagnetic exchange coupling observed in the diiron complex 1. Magnetic susceptibility data revealed an exchange coupling constant of J = − 173 cm–1, confirming its potential role as a model for non-heme diiron metalloenzymes. In contrast, complex 2 exhibits typical paramagnetic behavior of an octahedral Ni(II) complex with two unpaired electrons. Calculations based on density functional theory confirmed the high-spin state of the Fe(III) centers in the diiron complex and verified the magnitude of the strong antiferromagnetic exchange coupling. For the nickel complex, these calculations also revealed a significant degree of bond covalency, providing a comprehensive understanding of the structural and magnetic properties of these pyridoxal-based coordination compounds.