Abstract

A structural and magnetic characterization of a trinuclear chiral Mn(ll) formate three-dimensional framework exhibiting a triangular arrangement is presented. Compound Na3[Mn3(HCOO)9] was obtained by solvothermal synthesis and crystallizes in the chiral cubic space group P213 and is well described by a ? conformation. The structure displays triangular Mn3 building blocks, in which the metal centers are bonded by formate ligands in a syn-anti mode (Mn-Mn 5.697(1) ÅR). The coordination sphere of manganese(II) is completed by six oxygen atoms from six formate ligands, resulting in an octahedral geometry. Magnetic susceptibility measurements showed antiferromagnetic interactions at high temperature and a strongly field dependent magnetic behavior below 40 K. At fields higher than 1.0 kOe only the antiferromagnetic interactions can be observed. At applied fields lower than 1.0 kOe magnetic susceptibility becomes irreversible with maxima observed at 22 and 34 K. These maxima suggest a weak ferromagnetic behavior because of spin canting, allowed by the presence of the noncentrosymmetric syn-anti HCOO bridges linking the Mn sites. This non-collinear antiferromagnetism and irreversible behavior can be due to the existence of a high degree of frustration in this unique lattice composed of linked triangular arrangements of interacting magnetic centers. © 2009 American Chemical Society.