Syntheses, Structures, and Luminescence Properties of Lanthanide Coordination Polymers with a Polycarboxylic Terpyridyl Derivative Ligand

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: {[Ln(2)L(2)]center dot H2O}(n) (Ln=Pr (1), Nd (2), Sm (3), Eu (4)), {[Ln(5)L(4)-(COO)(3)(H2O)(4)]center dot 10H(2)O}(n) (Ln=Tb (5), Dy (6)), and [Yb2L2(H2O)(2)]center dot 2H(2)O (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.