Synthesis, structures and properties of Mn(II) coordination frameworks based on R-isophthalate (R = -CH3 or -C(CH3)(3)) and various dipyridyl-type co-ligands

Five new Mn(II) metal-organic coordination polymers, [Mn(tbip)(bipy)](n) (1), {[Mn(tbip)(dpe)].1.5H(2)O}(n) (2), [Mn(tbip)(bpa)](n) (3), [Mn(mip)(bpa)](n) (4) and {[Mn-3(mip)(2)(Hmip)(2)(bpp)(2)(H2O)(2)].2H(2)O}(n) (5), were prepared through hydrothermal reactions of Mn(II) acetate with H(2)tbip (H(2)tbip = 5-tert-butyl isophthalic acid) or H(2)mip (H(2)mip = 5-methylisophthalic acid) in the presence of different dipyridyl co-ligands (bipy 4,4'-bipyridine, dpe = 1,2-bi(4-pyridyl) ethene, bpa 1,2-bi(4-pyridyl) ethane and bpp 1,3-di(4-pyridyl) propane). All these compounds were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. The structures of 1 and 2 are constructed of [Mn-2(tbip)2](n) layers, which consist of alternate left-and right-handed helical chains, and further pillared by bipy or dpe ligands into a 3D porous framework. Interestingly, there are two different sizes of pores in 1 and 2. From the topology point of view, both complexes 1 and 2 exhibit the rare rob network based on the dimeric [Mn(COO)](2) subunits as the 6-connected nodes. The ribbon-like chains having 8-and 16-membered rings in 3 and 4 result from dimeric Mn(II) units bridged by H(2)tbip or H(2)mip ligands, which are connected by the flexible dpa into 2D open layers. Complex 5 contains rare isophthalato-bridged trimanganese clusters as building units, which are further linked by mip anions to form a one-dimensional ladder-like chain with less common unidentate coordinated bpp decorated as pendants. The thermal stabilities and X-ray powder diffraction studies indicate that the microporous framework of 2 can keep stable even after the loss of guest water molecules. In addition, dominant antiferromagnetic coupling was observed in compounds 1-3 and 5.