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Tetranuclear Ni4 cubane complexes with high χT maxima: magneto-structural analysis

Abstract

A series of seven tetranuclear Ni(II) cubane-like complexes of general formulae [Ni4L4(ROH)4] (1 - 3) and [Ni4L4(R1OH)x(R2OH)y] (x=y=2 for complex 6, x=1, y=3 for complexes 4, 5 and 7; R = ‒C3H7, ‒C4H9, ‒C5H11; R1 and R2 = ‒CH3, ‒C2H5, ‒C3H7, ‒C4H9, ‒C5H11; L = N–(2–hydroxy–5–methylphenyl)salicylideneimine), was synthesized and their structural and magnetic properties were correlated in order to find out if there is any influence of the type of coordinated alcohol on magnetic properties. Molecular structures reveal octahedral coordination around nickel via five oxygen donor atoms and imino nitrogen atom. Three out of five oxygen atoms derive from imine and one from phenolate part of the Schiff base ligand, while the fifth derives from neutral ROH ligand. Distortion of cubane topology has been identified by Ni−O−Ni angle values and by O∙∙Ni∙∙O dihedral angle values. The intramolecular hydrogen bonds are various and rich being of the O-H···O type, spanning cubane core and probably being one of the dominant causes of its distortion. Other weak intramolecular hydrogen bonds of the C-H···N type are present in complexes 1, 2, 3, 5 and 7. The third very weak C-H···O intramolecular hydrogen bonds are responsible for supramolecular architecture of complexes 2, 5 and 6. The intermolecular hydrogen bonds are present only in the crystal structures of complexes 2, 5 and 6. An unexpected high maximum of the χT(T) curve, above 20 emuK/molOe is observed in some of the complexes. Significantly high χT maxima come from the quadratic spin-spin interactions depicted in the ZFS term as a consequence of the influence of the structural distortions and intermolecular interactions in the magnetic environment of Ni(II) ions. The influence of this contribution to the magnetic behaviour is revised in the known magneto-structural correlation between the values of the parameters of magnetic interaction J and the average Ni−O−Ni angle. Influence of the other structural characteristics, the average angle between O∙∙Ni∙∙O planes and the average angle between one O∙∙Ni∙∙O plane and Ni∙∙Ni vector, on the values of the parameters of magnetic interaction J are also analysed.

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Publication details

The article was received on 10 Apr 2018, accepted on 31 May 2018 and first published on 31 May 2018


Article type: Paper
DOI: 10.1039/C8CE00566D
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Tetranuclear Ni4 cubane complexes with high χT maxima: magneto-structural analysis

    F. Torić, G. Pavlović, D. Pajić, M. Cindric and K. Zadro, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C8CE00566D

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