Mn(II) coordination polymers assembled from 8 or 9-connected trinuclear secondary building units: topology analysis and research of magnetic properties

Two new Mn(II) coordination polymers, namely {[Mn3L2(pbbm)]center dot CH3CN}(n) (1) and [Mn3L2(CH3CN)(2)](n) (2) (pbbm = 1,1'-(1,5-pentane)bis-benzimidazole) have been prepared using a 3,4-bi(4-carboxyphenyl)benzoic acid (H3L) ligand under solvothermal conditions. Single-crystal X-ray diffraction studies indicate that 1 and 2 are both three-dimensional frameworks composed of trinuclear Mn(II) subunits. A topological analysis manifests that 1 is a 3-nodal (3,4,9)-connected new topology with a Schl fli symbol of (3.4(2))(3.4(2) 6(3)) (3(4).4(6).5(6).6(14).7(6)); while 2 is a 4,8-c flu network topology with a Schl fli symbol of (4(6))(4(12).6(12).8(4)). 1 and 2 possess excellent chemical resistance to boiling water and organic solvents. Variable temperature magnetization measurements (chi(T-T)(M) and chi(-1)(M)-T) make it clear that both complexes display ferrimagnetic interactions in the low-temperature region. The values from field-dependent magnetization measurements, M(H), do not reach clear saturation because of the magnetic anisotropy of the polycrystalline sample. Using alternating current (AC) susceptibility measurements, frequency-dependent peaks do not appear in all in-phase (chi') and out-of-phase (chi '') curves, indicating that there is no slow relaxation behavior of the magnetization. Markedly, the field-cooled (FC) and zero-field-cooled (ZFC) data of 1 display a divergence over the temperature range of 40-3.5 K, which could be on account of long-range magnetic ordering, or the impact of superparamagnetic behavior. Especially, 2 is based on a typical -J(1)J(1)J(2)-sequence, featuring a ferrimagnetic chain with a (5/2, 10/2) spin topology.