Synthesis, structures and properties of alkaline earth metal benzene-1,4-dioxylacetates with three-dimensional hybrid networks

Three novel alkaline earth metal benzene-1,4-dioxylacetates M(L)H2O (M = Ca, Sr or Ba, L = benzene-1,4-dioxylacetate) with three-dimensional (3D) hybrid frameworks were reported. Both Ca(L)H2O (1) and Sr(L)H2O (2) crystallize in the monoclinic space group P21/c while Ba(L)H2O (3) in the monoclinic space group P21. As determined by X-ray single-crystal analysis, in these compounds each metal ion is coordinated by eight O atoms: four from different carboxylate groups, two from one carboxylate group, one from the ether oxygen and one from one water molecule. Each L2− ligand coordinates to five alkaline earth metal centers through one of its ether oxygen atoms and two carboxylate groups adopting novel μ3-η2:η2-bridging and μ2-η1:η1-bridging coordination modes to give rise to a 3D network. The luminescence analysis shows that complexes 1 and 2 exhibit fluorescence in the solid state at room temperature.