Popis: |
Solvothermal reactions of lanthanide chloride with a new ligand, H3L, 4′-(3-carboxylpyridyl)-2,2′:6′,2“-terpyridine-6,6”-dicarboxylic acid, yields seven new lanthanide–organic frameworks: {[Ln2L2]⋅H2O}n (Ln=Pr (1), Nd (2), Sm (3), Eu (4)), {[Ln5L4(COO)3(H2O)4]⋅10 H2O}n (Ln=Tb (5), Dy (6)), and [Yb2L2(H2O)2]⋅2 H2O (7). Single-crystal X-ray diffraction reveals that these complexes belong to three structural types. Type I (1–4) consists of lanthanide–carboxyl group layers pillared by L3− to form a three-dimensional network. Type II (5 and 6) comprises a right-handed helical chain and a left-handed helical chain linked through L3− anions into a three-dimensional framework. Type III (7) is a discrete dinuclear structure. The structural change is due to the decrease in the metal coordination number from nine for the large ions to seven for the small ions; this demonstrates the effect of lanthanide contraction. These materials exhibit high thermal stability. In addition, the luminescent properties of these complexes are discussed. |