One-dimensional coordination polymers of antiferromagnetically-coupled [Mn-4] single-molecule magnets

Reactions of the rhombic [(Mn2Mn2III)-Mn-II(hmp)(6)](4+) complex in acetonitrile with simple carboxylate ligands yield (i) three new isolated [Mn-4] complexes, namely [Mn-4(hmp)(6)(CH3COO)(2)(H2O)(2)](ClO4)(2)center dot 4H(2)O (1), [Mn-4(hmp)(6)(CCl3COO)(2)(H2O)(2)](ClO4)(2) (2) and [Mn-4(hmp)(6)(C6H5COO)(2)(H2O)(2)](ClO4)(2)center dot 4CH(3)CN center dot 2H(2)O (3) in the presence of either bulky carboxylate or of an excess of Mn(II) source; and (ii) two 1D arrangements of [Mn-4] complexes connected through double syn-syn carboxylate bridges when using acetate and chloroacetate, namely {[Mn-4(hmp)(6)(CH3COO)(2)](ClO4)(2)center dot H2O}(n) (4) and {[Mn-4(hmp)(6)(ClCH2COO)(2)](ClO4)(2)center dot 2H(2)O}(n) (5). The assembly of such building blocks can thus be controlled by an adequate choice of the bridging anion. As expected, the isolated [Mn-4] complexes behave as Single-Molecule Magnets as shown by the study of their static and dynamic magnetic properties. Detailed magnetic studies both on polycrystalline samples and single crystals show that the chain compounds are isolated antiferromagnetic chains. The slow relaxation of their staggered magnetization has been studied thanks to finite-size effects induced by the intrinsic defects of the material.