| Summary: | Here we present the synthesis, structure and magnetic properties of complexes of general formula (Mn)(Me<sub>2</sub>NH<sub>2</sub>)<sub>4</sub>][Mn<sub>3</sub>(μ-L)<sub>6</sub>(H<sub>2</sub>O)<sub>6</sub>] and (Me<sub>2</sub>NH<sub>2</sub>)<sub>6</sub>[M<sub>3</sub>(μ-L)<sub>6</sub>(H<sub>2</sub>O)<sub>6</sub>] (M = Co<sup>II</sup>, Ni<sup>II</sup> and Cu<sup>II</sup>); L<sup>−2</sup> = 4-(1,2,4-triazol-4-yl) ethanedisulfonate). The trinuclear polyanions were isolated as dimethylammonium salts, and their crystal structures determined by single crystal and powder X-ray diffraction data. The polyanionic part of these salts have the same molecular structure, which consists of a linear array of metal(II) ions linked by triple N1-N2-triazole bridges. In turn, the composition and crystal packing of the Mn<sup>II</sup> salt differs from the rest of the complexes (with six dimethyl ammonia as countercations) in containing one Mn<sup>+2</sup> and four dimethyl ammonia as countercations. Magnetic data indicate dominant intramolecular antiferromagnetic interactions stabilizing a paramagnetic ground state. Susceptibility data have been successfully modeled with a simple isotropic Hamiltonian for a centrosymmetric linear trimer, H = −2J (S<sub>1</sub>S<sub>2</sub> + S<sub>2</sub>S<sub>3</sub>) with super-exchange parameters J = −0.4 K for Mn<sup>II</sup>, −7.5 K for Ni<sup>II</sup> and −45 K for Cu<sup>II</sup> complex. The magnetic properties of these complexes and their easy processing opens unique possibilities for their incorporation as magnetic molecular probes into such hybrid materials as magnetic/conducting multifunctional materials or as dopant for organic conducting polymers.
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