Lanthanide Coordination Polymers Constructed from Imidazole-4,5-Dicarboxylate and Sulfate: Syntheses, Structural Diversity, and Photoluminescent Properties

Three series of lanthanide coordination polymers of {[Ln2(HIDC)2(SO4)­(H2O)5]·H2O}n (CPs-1Ln, Ln = Sm, Eu, Tb, Dy, Ho, Er, and Yb), {(H2prz)­[Ln2(HIDC)2(SO4)2]}n (CPs-2Ln, Ln = Sm and Eu), and [Ln2(HIDC)2(SO4)­(H2O)2]n (CPs-3Ln, Ln = Tb, Dy, Ho, Er, and Yb) have been hydrothermally synthesized by the reactions of Ln­(NO3)3·6H2O with imidazole-4,5-dicarboxylic acid (H3IDC) and sulfuric acid (H2SO4) in the presence of piperazine (prz) at different temperatures. The results of the single-crystal X-ray diffraction analysis reveal that CPs-1Ln presents a three-dimensional (3D) architecture, in which alternating one-dimensional (1D) right-/left-handed helical chains of [Ln2(HIDC)2]∞ are interlinked by μ3-SO42– anions. CPs-2Ln assumes a H2prz2+ templated 3D anionic layer-pillared metal–organic framework (MOF) of {[Ln2(HIDC)2(SO4)2]}n2n–, in which two-dimensional (2D) (6,3) network layers of [Ln2(HIDC)2]n2n+ are pillared by μ2-SO42– anions. CPs-3Ln is a 2D layer structure, in which two 2D (6,3) monolayers of [Ln2(HIDC)2(H2O)2]n2n+ are connected by μ2-SO42– anions to form a 2D double-layer structure. The adjacent 2D double-layers are further stacked together via strong hydrogen bonding interactions to generate a 3D supramolecular framework. In addition, the results of photoluminescent measurements for Sm (1Sm and 2Sm), Eu (1Eu and 2Eu), Tb (1Tb and 3Tb), and Dy (1Dy and 3Dy) compounds in the solid state at room temperature indicate that different structural types have a different influence on their characteristic photoluminescences.