A new three-dimensional manganese(II) coordination polymer based on the 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene ligand

The self-assembly of coordination polymers and the crystal engineering of metal-organic coordination frameworks have attracted great interest, but it is still a challenge to predict and control the compositions and structures of the complexes. Employing multidentate organic ligands and suitable metal ions to construct inorganic-organic hybrid materials through metal-ligand coordination and hydrogen-bonding interactions has become a major strategy. Recently, imidazole-containing multidentate ligands that contain an aromatic core have received much attention. A new three-dimensional Mn-II coordination polymer based on 1,3,5-tris[(1H-imidazol-1-yl) methyl] benzene, namely poly[(ethane1,2-diol-kappa O)(mu-sulfato-kappa O-2:O'){mu(3)-1,3,5-tris[(1H-imidazol-1-yl) methyl]benzene-kappa N-3:N':N"} manganese(II)], [Mn(SO4)(C18H18N6)(C2H6O2)](n), was synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Crystal structural analysis shows that there are two kinds of crystallographically independent Mn-II centres, each lying on a centrosymmetric position and having a similar six-coordinated octahedral structure. One is coordinated by four N atoms from four 1,3,5-tris[(1H-imidazol-1-yl)methyl] benzene (timb) ligands and two O atoms from two different bridging sulfate anions. The second is surrounded by two timb N atoms and four O atoms, two from sulfate anions and two from two ethane-1,2-diol ligands. The tripodal timb ligand bridges neighbouring Mn-II centres to generate a two-dimensional layered structure running parallel to the ab plane. Adjacent layers are further bridged by sulfate anions, resulting in a three-dimensional structure with 3,4,6-c topology. Thermogravimetric analysis of the title polymer shows that it is stable up to 533 K. The first weight loss between 533 and 573 K corresponds to the release of coordinated ethane-1,2-diol molecules, and further decomposition occurred at 648 K.