1D Coordination polymers constructed from anti-anti carboxylato-bridged Mn(III)(3)O(Brppz)(3) units: from long-range magnetic ordering to single-chain magnet behaviors.

Abstract

The coordination of methanol and ethanol molecules was observed in the construction of three 1D coordination polymers composed of anti-anti carboxylato-bridged Mn(III)(3)O(Brppz)(3) units [Brppz = 3-(5-bromine-2-phenolate)pyrazolate]. The difference in these 1D complexes' structures induced by methanol and ethanol solvents leads to the variation of the magnetic properties. The methanol solvent product 1 [Mn(III)(3)O(Brppz)(3)(MeOH)(3)(AcO)].0.5MeOH has a Mn(III)(3)O repeating unit with two octahedral configuration manganese(III) ions and one square-pyrimid configuration manganese(III) ion, showing a long-range magnetic ordering with a T(c) of 8.2 K, whereas the ethanol solvent products 2 [Mn(III)(3)O(Brppz)(3)(C(2)H(5)OH)(4)(AcO)] (alpha-phase) and 3 [Mn(III)(3)O(Brppz)(3)(C(2)H(5)OH)(4)(AcO)] (beta-phase) are polymorphs, both having a Mn(III)(3)O repeating unit with three octahedral configuration manganese(III) ions, displaying single-chain magnet behaviors. Products 2 and 3 represent the first examples of polymorphs of single-chain magnets. Furthermore, the bridging carboxylate ligand in these 1D complexes was generated by the decomposition of beta-diketones via the retro-Claisen condensation reactions in the presence of strong bases.