Solvothermal synthesis, structure and magnetism of two novel 3D metal-organic frameworks based on infinite helical Mn–O–C rod-shaped building units

Two novel coordination polymers Mn3(BTC)2(DMF)4 1 and Mn3(BTC)2(DMF)3(Pyd) 2 have been synthesized under solvothermal conditions and structurally characterized. Crystal data for 1: monoclinic P21/c, a = 17.876(4) Å, b = 11.797(2) Å, c = 18.848(4) Å, β = 116.35(3)°, Z = 4. Crystal data for 2: monoclinic P21/c, a = 17.711(4) Å, b = 11.849(2) Å, c = 18.903(4) Å, β = 114.86(3)°, Z = 4. In the structures, the carboxyl groups of BTC ligands bridge the metal centers to form infinite helical Mn–O–C rod-shaped building units running along the 21 screw axes. Meanwhile the adjacent helical rods twist each other via benzene rings of BTC ligands to lead to a three-dimensional network with one-dimensional about 6 × 8 Å2 quadrangular channels along the [100] direction. TGA, IR and magnetic properties have been investigated.