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

TLDR: In this paper, the properties of Mn(II) metal-organic coordination polymers were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction.

Abstract: Five new Mn(II) metal–organic coordination polymers, [Mn(tbip)(bipy)]n (1), {[Mn(tbip)(dpe)]·1.5H2O}n (2), [Mn(tbip)(bpa)]n (3), [Mn(mip)(bpa)]n (4) and {[Mn3(mip)2(Hmip)2(bpp)2(H2O)2]·2H2O}n (5), were prepared through hydrothermal reactions of Mn(II) acetate with H2tbip (H2tbip = 5-tert-butyl isophthalic acid) or H2mip (H2mip = 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 [Mn2(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 H2tbip or H2mip 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.