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ABSTRACT: Reactions of rare earth benzoate and nickel perchlorate with a Schiff-base ligand, 2-([(2-hydroxyphenyl)imino]methyl) phenol (H(2)L), in the presence of triethylamine yielded three heterobimetallic octanuclear clusters of general formula [RE(3)Ni(5)L(5)(PhCOO)(3)(μ(3)-OH)(5)(μ(3)-OCH(3))(CH(3)OH)(4)(H(2)O)]·xCH(3)OH·yH(2)O (RE = Dy(III), x = 4, y = 4 (), RE = Gd(III), x = 5, y = 4 (), RE = Y(III), x = 5, y = 3 ()). Single-crystal X-ray diffraction reveals that the metal core of each cluster consists of two distorted [RE(2)Ni(2)O(4)] cubane-like moieties and a heterobimetallic triangular [RE(2)NiO(2)] unit, with RE ions arranged in a typical triangular fashion. Variable-temperature solid state magnetic susceptibilities of these complexes were measured in the temperature range 2-300 K and the results indicate that an overall ferromagnetic interaction among the metal ions is operative for compounds and . Under zero external field, the Dy(3)Ni(5) compound shows a frequency dependence of the out-of-phase (χ'') signals, which indicates slow relaxation of the magnetization.
Dalton Transactions 02/2013; · 3.84 Impact Factor
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ABSTRACT: A series of mixed-valent heterometallic pentanuclear Co(III)(3)Co(II)RE(III) (RE = Gd (1), Tb (2), Y (3)) clusters have been rationally assembled by taking advantage of a bifunctional ligand with o-vanillin and tripodal tris(hydroxymethyl)aminomethane units. Structural determinations reveal that all compounds are isomorphous and possess a T-shaped Co(4)RE core, which comprises two nearly linear Co(2)RE subunits sharing a common RE ion. Their magnetic properties were thoroughly studied. The static magnetic susceptibility studies of 1 demonstrate the presence of weak ferromagnetic interactions between the magnetic centres and magnetic anisotropy reflected by the single ion zero-field splitting (ZFS) D term. Both 1 and 2 behave magnetically as heterodinuclear metal systems, while the magnetic behaviour of 3 is identical to an isolated Co(II) ion. Moreover, alternating-current susceptibility measurements did not exhibit any out-of-phase signal, suggesting that slow magnetic relaxation is absent above 2 K within them. These isomorphous Co(4)RE clusters offer an opportunity to systematically probe the contribution of different metal ions to the overall magnetic behaviour in Co(II)-RE(III) systems.
Dalton Transactions 07/2012; 41(32):9760-5. · 3.84 Impact Factor
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ABSTRACT: Two Dy(3) triangles encapsulated inside the cavity of a macrocycle ligand have been successfully synthesized, providing a unique opportunity to probe the relaxation dynamics of the complexes by altering the axial ligands.
Chemical Communications 06/2012; 48(55):6924-6. · 6.17 Impact Factor
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ABSTRACT: Two linear tetranuclear lanthanide complexes of general formula [Ln(4)(L)(2)(C(6)H(5)COO)(12)(MeOH)(4)], where HL = 2,6-bis((furan-2-ylmethylimino)methyl)-4-methylphenol, () and Ln(III) = Dy(III) (1) and Gd(III) (2), have been synthesized and characterized. The crystal structural analysis demonstrates that two Schiff-base ligands inhibit the growth of benzoate bridged 1D chains, leading to the isolation of discrete tetranuclear complexes due to their steric hindrances. Every Ln(III) ion is coordinated by eight donor atoms in a distorted bicapped trigonal-prismatic arrangement. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency- and temperature-dependent out-of-phase signal under zero dc field, typical of single-molecule magnet (SMM) behaviour with an anisotropic barrier Δ(eff) = 17.2 K.
Dalton Transactions 02/2012; 41(11):3248-52. · 3.84 Impact Factor
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ABSTRACT: We described the syntheses, crystal structures, and magnetic behavior of a novel series of heterometallic [Ni(4)M(2)] [M = Gd (1), Dy (2) and Y (3)] hexanuclear compounds afforded by the reaction of rare-earth(III) nitrate, nickel(II) acetate, and Schiff-base ligand 2-(2-hydroxy-3-methoxybenzylideneamino)phenol (H(2)L) in a mixture of ethanol and dichloromethane in the presence of triethylamine. Single-crystal X-ray diffraction measurements reveal that all three compounds have a metal core made up of two Ni(2)MO(4) defective cubanes. The magnetic properties of all compounds have been studied. Solid-state direct-current magnetic susceptibility analyses demonstrate competing antiferromagnetic and ferromagnetic interactions within both compounds 1 and 3. Solid-state alternating-current magnetic susceptibility investigations show a frequency-dependent out-of-phase signal for compound 2 below 4 K, suggestive of slow magnetic relaxation.
Inorganic Chemistry 02/2012; 51(4):2699-705. · 4.60 Impact Factor
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ABSTRACT: Reactions of lanthanide perchlorates and manganese acetate with Schiff-base ligand (H(4)L = 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol) in methanol in the presence of triethylamine yielded two hexanuclear heterometallic clusters of general formula [Mn(4)(ΙΙΙ)Ln(2)(ΙΙΙ)(H(2)L)(2)(HL)(2)(CH(3)COO)(4)(CH(3)O)(2)(CH(3)OH)(4)](ClO(4))(2)·6CH(3)OH [Ln = La(ΙΙΙ) (1), Nd(ΙΙΙ) (2)]. 1 and 2 are isostructural, with the metal centres consisting of a nonplanar [Mn(4)(ΙΙΙ)Ln(2)(ΙΙΙ)(μ(2)-O)(8)(μ(3)-OR)(2)](8+) core. Variable-temperature solid state magnetic susceptibilities measurements of 1 and 2 in the temperature 2-300 K were performed, indicating dominant antiferromagnetic exchange interactions between the metal centres in both compounds. Alternating current (ac) susceptibility data for 2 displays out-of-phase signal suggesting slow relaxation of magnetization whereas no out-of-phase signal is observed in 1, highlighting the incorporation of lighter lanthanide leads to SMM property.
Dalton Transactions 12/2011; 41(8):2314-9. · 3.84 Impact Factor
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ABSTRACT: The asymmetric Cole-Cole plots observed in a remarkable linear Dy(III) compound suggests the occurrence of multiple relaxations most likely associated with distinct anisotropic centres, thus opening new avenues for investigating the relaxation dynamics of lanthanide aggregates.
Chemical Communications 09/2010; 46(33):6057-9. · 6.17 Impact Factor
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ABSTRACT: Two new dysprosium(III) coordination compounds, namely, [Dy(4)(HL)(4)(C(6)H(4)NH(2)COO)(2)(mu(3)-OH)(4)(mu-OH)(2)(H(2)O)(4)].4CH(3)CN.12H(2)O (1) and Dy(8)(HL)(10)(C(6)H(4)NH(2)COO)(2)(mu(3)-OH)(8)(OH)(2)(NO(3))(2)(H(2)O)(4)] (2), have been synthesized from the Schiff-base ligand 2-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid (H(2)L) and dysprosium chloride (1) or dysprosium nitrate (2). Single-crystal X-ray diffraction studies reveal that compound 1 exhibits a tetranuclear cubane-like structure and that 2 is an octanuclear, bis-cubane complex. The [Dy(4)(mu (3)-OH)(4)] cubane cores of 1 and 2 are structurally related; however, the magnetic properties of 1 and 2 are drastically different. Indeed, 2 shows slow relaxation of magnetization while no out-of-phase alternating current (ac) signal is noticed for 1. These significant disparities are most likely due to the different M-O-M angles observed for the respective cubane cores.
Inorganic Chemistry 08/2010; 49(16):7549-57. · 4.60 Impact Factor
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Chemistry 10/2009; 15(40):10335-8. · 5.93 Impact Factor
