Two tetranuclear cubane-like nickel(II) complexes of formula [Ni4(CH3O)4(L1)4(CH3OH)4] (1) and [Ni4(CH3O)4(L2)4(CH3OH)4] (2) (HL1 = 2-hydroxybenzaldehyde and HL2 = 2-hydroxy-5- methylbenzaldehyde) have been prepared by the reaction of NiCl2·6H2O with methanolic solutions of HL1 and HL2 in the presence of triethylamine at room temperature. Complexes 1 and 2 have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. The X-ray crystal structure analysis revealed that 1 and 2 have a cubane-type structural topology with four Ni(II) ions and four methoxo-oxygen atoms regularly alternating at the corners. Each metal ion in 1 and 2 is sixcoordinate in a distorted octahedral geometry defined by three bridging methoxo-oxygens, one oxygen atom from a methanol molecule and two oxygen atoms from the bidentate L1 (1)/L2 (2) ligands. The magnetic properties of 1 and 2 were investigated in the temperature range 1.9–300 K. They are indicative of an overall ferromagnetic behaviour, the decrease in the very low temperature region being due to zero-field splitting and intermolecular interactions. A detailed analysis of the magnetic data of 1 and 2 assuming an idealized D2d symmetry for the Ni4O4 unit shows the occurrence of a low-lying spin nonet and two opposite magnetic interactions, one being ferromagnetic [Ja = +12.6 (1) and +10.5 cm⁻¹ (2)] and the other antiferromagnetic [Jb = -4.10 (1) and -2.10 cm⁻¹ (2)]. These values fit well the linear correlation between the exchange coupling parameter (J) and the Ni–O–Ni angle (a) which was established for Ni4O4 cubane motifs in previous works.
Effects of electron donating/withdrawing groups in the 5-substituted-2-hydroxybenzaldehyde on the synthesis of neutral cubanes with a NiII4O4core: Synthesis, crystal structures and magnetic properties
Rudbari, Hadi Amiri
Primo
Membro del Collaboration Group
;Bruno, GiuseppePenultimo
Membro del Collaboration Group
;
2016-01-01
Abstract
Two tetranuclear cubane-like nickel(II) complexes of formula [Ni4(CH3O)4(L1)4(CH3OH)4] (1) and [Ni4(CH3O)4(L2)4(CH3OH)4] (2) (HL1 = 2-hydroxybenzaldehyde and HL2 = 2-hydroxy-5- methylbenzaldehyde) have been prepared by the reaction of NiCl2·6H2O with methanolic solutions of HL1 and HL2 in the presence of triethylamine at room temperature. Complexes 1 and 2 have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. The X-ray crystal structure analysis revealed that 1 and 2 have a cubane-type structural topology with four Ni(II) ions and four methoxo-oxygen atoms regularly alternating at the corners. Each metal ion in 1 and 2 is sixcoordinate in a distorted octahedral geometry defined by three bridging methoxo-oxygens, one oxygen atom from a methanol molecule and two oxygen atoms from the bidentate L1 (1)/L2 (2) ligands. The magnetic properties of 1 and 2 were investigated in the temperature range 1.9–300 K. They are indicative of an overall ferromagnetic behaviour, the decrease in the very low temperature region being due to zero-field splitting and intermolecular interactions. A detailed analysis of the magnetic data of 1 and 2 assuming an idealized D2d symmetry for the Ni4O4 unit shows the occurrence of a low-lying spin nonet and two opposite magnetic interactions, one being ferromagnetic [Ja = +12.6 (1) and +10.5 cm⁻¹ (2)] and the other antiferromagnetic [Jb = -4.10 (1) and -2.10 cm⁻¹ (2)]. These values fit well the linear correlation between the exchange coupling parameter (J) and the Ni–O–Ni angle (a) which was established for Ni4O4 cubane motifs in previous works.File | Dimensione | Formato | |
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6_RSC Adv., 2016, 6, 7189.pdf
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