Four novel alkaline-earth metal coordination polymers with networks controlled by the diverse coordination modes of amino-sulfonate ligand: Synthesis, crystal structures and luminescent properties

Four novel alkaline-earth metal coordination polymers based on 4,4′-diamino-2,2′-stilbenedisulfonic acid ligand (H2dsd), namely, [Mg(dsd)(H2O)4]n (1), {[Ca(dsd)(H2O)2]·H2O}n (2), {[Sr(dsd)(H2O)6]·H2O}n (3), [Ba(dsd)(H2O)2]n (4), were synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, single-crystal X-ray diffraction and thermogravimetric analysis. These complexes exhibit various polymeric networks due to the diverse coordination modes of dsd2−. Complexes 1 and 3 display a 1D zigzag chain structure with dsd2− group as a μ-bis(monodentate) ligand (denoted as μ2-η1η1 ligand). Complex 2 is a 1D ribbon chain coordination polymer in which dsd2− shows the μ3-η1η2η1 coordination mode, and complex 4 is a 2D coordination polymer in which dsd2− presents the unusual μ4-η1η2η1η1 coordination mode. The present four complexes exhibit different fluorescent emissions in the solid state at room temperature.