Abstract
Two novel low-dimensional molecular magnetic materials were prepared by the self-assembly of 3d- and 5d-metal complexes. These are the first neutral heterobimetallic cyanobridged compounds involving one anisotropic Mn(III) Schiff base complex and one octacyanotungstate(V) per molecular unit. A slow diffusion of the constituents’ solutions leads to the formation of the 0D crystalline complex 1, due to coordination of a water molecule to the Mn center, which prevents polymer formation. A rapid mixing of reagents results in the precipitation of the microcrystalline powder of complex 2, which based on the totality of experimental data, possesses a 1D polymeric structure. The magnetic studies have shown that antiferromagnetic exchange interactions prevail in 1 (J/kB = −13.1(7) K, D = −3.0(1.3) K, zJ' = −0.16(20) K and gav = 2.00(1)); while the presence of the significant intramolecular Mn(III)–W(V) ferromagnetic coupling through cyanide bridge is characteristic for 2 (J/kB = 46.1(5) K, gMn = 2.11(3), fixed gW = 2.0). Due to the weak interchain interactions, zJ′/kB = −0.8(2) K, and compound 2 is a metamagnet with the Néel temperature of 9.5 K undergoing a spin-flip transition at 2 kOe. The slow magnetization dynamics of 2 were investigated at a DC field of 0 and 2 kOe, giving the values of τ0 32(15) and 36(15) ps, respectively, well within the range typical for single-chain magnets (SCMs). The respective ∆τ/kB values were 48.4(1.2) and 44.9(1.0) K.
Highlights
Molecular magnets of low dimensionality represent polynuclear coordination compounds in which the paramagnetic ions linked together via bridging ligands are interesting due to the slow magnetic relaxation that a large group among them exhibit
For the zero-dimensional (0D) systems named single-molecule magnets (SMMs), the ∆A value depends on the total spin and the energy of uniaxial anisotropy of the molecule and can be expressed as ∆A = S2 |D| for the integer S and (S2 − 1/4)|D| for the half-integer S [4], where the axial zero-field splitting parameter D < 0
Slow magnetic relaxation has been found for one-dimensional (1D) coordination compounds, known as single chain magnets (SCMs) [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]
Summary
Molecular magnets of low dimensionality represent polynuclear coordination compounds in which the paramagnetic ions linked together via bridging ligands are interesting due to the slow magnetic relaxation that a large group among them exhibit. The use of heavier transition metal complexes in the design of low-dimensional nanomagnets has a few advantages First of all, they possess more diffuse valence orbitals than 3d metals that can offer stronger magnetic exchange interactions [32]. The assemblies of the paramagnetic [W(CN)8 ]3− precursor and manganese(III) Schiff base complex, [Mn(SB)]+ , are fairly limited and poorly studied in comparison with the large family of bimetallic compounds comprised of the [Mn(SB)]+ cation and the 3d metal hexacyanides that are extensively investigated both structurally and magnetically [76].
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