3-D Silver(I) Lanthanide(III) Heterometallic-Organic Frameworks Constructed from 2,2'-Bipyridine-3,3'-dicarboxylic Acid: Synthesis, Structure, Photoluminescence, and Their Remarkable Thermostability

A new family of silver(I)-lanthanide(III) heterometallicorganic frameworks having the formula [AgLn(bpdc)(2)] (Ln = Eu (1), Tb (2), Sm (3), Dy (4), Y (5), Yb (6), Er (7), Ho (8); H(2)bpdc = 2,2'-bipyridine-3,3'-dicarboxylic acid), each of which crystallizes in the monoclinic space group C2/c with Z = 4, has been hydrothermally synthesized. The compounds were characterized by means of IR, elemental analysis, thermogravimetric-differential thermal analysis, and powder X-ray diffraction (XRD), wherein compounds 1, 2, and 4-8 were structurally characterized. The powder XRD and single-crystal structures of the title compounds indicate that all the compounds are isostructural and feature a three-dimensional (3-D) open framework. In the structures of the compounds, bpdc(2-) ligands link Ln(3+) through their carboxylic groups, resulting in the formation of a one-dimensional {Ln(bpdc)(2)}(n) infinite chain along the c direction. The adjacent chains are then connected to each other through the coordination interaction between Ag+ and the pyridyl N atoms of bpdc(2-) ligands from the chains, resulting in a 3-D (2,4,6)-connected open framework with (4(11).6(4))(4(3).8(2).10)(8)(2) topology. The compounds show remarkable good thermally stability up to 370 degrees C because neither aquo ligands nor lattice water molecules exist in the composition of the compounds. The photoluminescent properties of compounds 1 and 2 were studied in detail. The energy level of the triplet states of the ligand H(2)bpdc 21 505 cm(-1) (465 nm) was determined based on the 77 K emission spectrum of the compound [Gd-2(bpdc)(3)(phen)(2)(H2O)(2)]center dot 6H(2)O 9. The D-5(0) and D-5(4) emission lifetimes (1.58 and 1.76 ms) and the overall quantum yields (21% and 22%) were determined for the compounds 1 and 2, respectively.