Abstract

Five pentanuclear heterometallic isostructural complexes, [Ni(4)Ln(L)(2)(LH)(2)(CH3CN)(3)Cl]center dot xH(2)O center dot yCH(3)OH {Ln = Y-III (1), Gd-III (2), Tb-III (3), Dy-III (4) and Er-III (5)} [for 1 and 2, x = 2, y = 1; for 3, x = 6, y = 2; for 4, x = 5, y = 1; for 5, x = 2, y = 2] were prepared by the reaction of (E)-2-(hydroxymethyl)-6-{[(2-hydroxyphenyl)imino]methyl}-4-methylphenol (LH3) with LnCl(3)center dot 6H(2)O and Ni(OAc)(2)center dot 4H(2)O in the presence of tetrabutylammonium hydroxide (TBA-OH) base. The structural characterization reveals that compounds 1-5 contain a spirocyclic pentanuclear core [Ni(4)Ln(mu(3)-O)(4)(mu(2)-O)(4)](3+) where two triangular motifs [Ni(2)Ln(mu(3)-O)(2)(mu(2)-O)(2)](3+) are fused together through a common vertex of the Ln(III) ion. The central Ln(III) ion forms an eight-coordinated distorted triangular dodecahedron geometry, while the nickel(II) ions form a distorted octahedron geometry. Comprehensive dc magnetic studies reveal that antiferromagnetic exchange interaction exists between the Ni-II centres. The ac susceptibility measurement revels that dysprosium and erbium analogue shows field induced slow magnetic relaxation with an anisotropic barrier (U-eff) of 25.12 cm(-1) and 22.13 cm(-1) respectively.