One-Dimensional Supramolecular Organization of Single-Molecule Magnets

Université Bordeaux 1, CNRS, Centre de Recherche Paul Pascal--UPR8641, 115 avenue du Dr. Albert Schweitzer, 33600 Pessac, France.
Journal of the American Chemical Society (Impact Factor: 12.11). 04/2007; 129(16):5045-51. DOI: 10.1021/ja067744i
Source: PubMed


An out-of-plane dimeric MnIII quadridentate Schiff-base compound, [Mn2(salpn)2(H2O)2](ClO4)2 (salpn(2-) = N,N'-(propane)bis(salicylideneiminate)), has been synthesized and structurally characterized. The crystal structure reveals that the [Mn2(salpn)2(H2O)2](2+) units are linked through weak H-bonds (OHwater...OPh) in one dimension along the c-axis, forming supramolecular chains. The exchange interaction between MnIII ions via the biphenolate bridge is ferromagnetic (J/kB = +1.8 K), inducing an ST = 4 ground state. This dinuclear unit possesses uni-axial anisotropy observed in the out-of-plane direction with DMn2/kB = -1.65 K. At low temperatures, this complex exhibits slow relaxation of its magnetization in agreement with a single-molecule magnet (SMM) behavior. Interestingly, the intermolecular magnetic interactions along the one-dimensional organization, albeit weak (J'/kB = -0.03 K), influence significantly the thermally activated and quantum dynamics of this complex. Thus, unique features such as M vs H data with multiple steps, hysteresis effects, and peculiar relaxation time have been explained considering SMMs in small exchange-field perturbations and finite-size effects intrinsic to the chain arrangement. The magnetic properties of this new complex can be regarded as an intermediate behavior between SMM and single-chain magnet (SCM) properties.

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    ABSTRACT: New Mn(III) complexes with Schiff bases and dicyanamide are synthesized: [Mn(Salpn)N(CN)2]n (two polymorphous modifications, Ia and Ib), {[Mn(5-BrSalen)N(CN)2] · CH3OH}n (II), and [Mn(3-MeOSalen)N(CN)2(H2O)] (III), where SalpnH2 = N,N′-bis(salicylidene)-1,3-diaminopropane, 5-BrSalenH2 = N,N′-bis(5-bromosalicylidene)-1,2-diaminoethane, and 3-MeOSalenH2 = N,N′-bis(3-methoxysalicylidene)-1,2-diaminoethane. Complexes Ia, Ib, and II have the polymer structure in which the dicyanamide anion binds the paramagnetic Mn(III) complexes with the Schiff bases into one-dimensional chains. Unlike them, in complex III the monomer units containing water and the dicyanamide anion as terminal ligands form dimers due to hydrogen bonds. The study of the magnetic properties of complexes Ia and II shows a weak antiferromagnetic interaction between the Mn3+ ions through the dicyanamide bridges in these complexes.
    No preview · Article · Feb 2013 · Russian Journal of Coordination Chemistry
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    ABSTRACT: The solvent-mediated crystal-to-crystal transformation was observed from yellow crystal of NiCl2(CH3OH)2(1,4-dioxane)0.5 (1) to green crystal of [NiCl2(H2O)2(1,4-dioxane)](1,4-dioxane) (2) under high humidity or adding of H2O in CH3OH/1,4-dioxane solution. The μ-Cl2 bridge in 1 replaced by 1,4-dioxane bridge in 2. In 1, the chlorine-bridged linear chains of NiCl2(CH3OH)2 and 1,4-dioxane molecules stack along the b- and c-axis alternatively with hydrogen bonds intrachain, interchain, between chain and solvent. These hydrogen bonds and dipolar interaction between ferromagnetic coupling chlorine-bridged chains result in long-range ferromagnetic ordering at 3.1K and a strong frequency dependence of the ac-susceptibilities associated to domain structures with very large shape anisotropy was observed below 3.1K. In 2, layers of 1,4-dioxane-bridged linear chains of NiCl2(H2O)2(1,4-dioxane) are intercalated by layer of 1,4-dioxane molecules with hydrogen bonds between chain and solvent. Compound 2 is paramagnet to 2K.
    No preview · Article · Nov 2011 · Polyhedron
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    ABSTRACT: In the title complex, [Mn(C(18)H(12)N(4)O(2))(N(3))(CH(4)O)], the Mn(III) ion is in a distorted octa-hedral coordination environment. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds connect mol-ecules into centrosymmetric dimers.
    Preview · Article · Jan 2007 · Acta Crystallographica Section E Structure Reports Online
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