Effects of calcium ions on crystal structure and luminescence properties of six rare earth metal complexes

Six heterometallic complexes ([Ln(2)(PYde)(6)Ca-3(H2O)(12)]center dot mH(2)O}(n) (Ln = Tb (1), m = 16; Eu (2), m = 14; Sm (3), m = 16; H2pydc = pyridine-2,6-dicarboxylic acid) and [Ln(2)(pydc)(6)Ca-2(H2O)(10)]center dot 2Him center dot xH(2)O (Ln = Tb (4), x = 8; Eu (5), x = 6; Sm(6), x = 8; im = imidazole) have been hydrothermally synthesized and characterized by elemental analysis, IR, TG, XRD as well as single-crystal X-ray diffraction. Complexes 1-3 display threedimensional network structure and can be simplified to a new topology, with the point symbol of {4.8(4).12}(2){4(2).8(2).10(2)}{8}(2). Complexes 4-6 exhibit tetranuclear structures. The luminescence properties for the six complexes were determined using solid samples. They show characteristic emission spectra of lanthanide ions. The complexes 1-6 were compared in terms of emission intensity, fluorescence decay lifetime and quantum yield. The quantum yields Phi(total) are 90.02 +/- 10%, 81.05 +/- 10%, 37.65 +/- 10%, and 70.84 +/- 10% for complexes 1 (Ca-Tb), 4 (Ca-Tb), 2 (Ca-Eu), and 5 (Ca-Eu), respectively. The effects of the structure of the complexes and the coordination of calcium ions on the luminescent properties of lanthanide complexes were also investigated.