Syntheses Structures And Luminescent Properties Of Lanthanide Coordination Polymers With Aromatic Dicarboxylate Ligands

Seven novel lanthanide coordination polymers based on2,4′–biphenyl–dicarboxylic acid （2,4′–H₂bpdc）,1,4–benzenedicarboxylic acid （1,4–H₂BDC）, andN,N′–bis（ethy lacetate）biimidazole （L） ligands from2D layer to3D network havebeen synthesized under hydro（solvo）thermal conditions by changing the molarratio between lanthanide nitrate and the ligands, pH value as well as the reactionsolvent. The structures of these seven lanthanide coordination polymers arecharacterized by ele mental analyses, IR spectroscopy, and single–crystal X–raydiffraction. The luminescent properties of the complexes are characterized byfluorescent spectra.Aromatic multicarboxylate acid such as2,4′–H₂bpdc and1,4–H₂BDC areselected to react with lanthanide nitrate. Four2D lanthanide coordination polymers（1⁴）{[Ln（bpdc）（BDC）_0.5（DMF）（H₂O）]·1.5H₂O}_n[Ln=Sm（1）, Tb（2）, Dy（3）, andGd（4）] were obtained. The results of single–crystal X–ray diffraction analysesind icates that complexes1⁴are isostructural. The2D layers are connected bybpdc2–and BDC2–ligands. They are stably stacked into3D supermolecule viahydrogen bonds and p–π interactions.Single aromatic dicarboxylate ligand2,4′–H₂bpdc is used to synthesize2Ddysprosium–coordination polymer, it′s formula is [Dy（bpdc）（DMF）₂（NO₃）₃]n（5）.From the topological view, complex5can be simplized （4,4） networks containing8–ring channe ls, the pore size of the8–ring is16.53×7.66. A noveleuropium–coordination polymer:[Eu（BDC）_1.5（DMF）（H₂O）]n（6） was constructedby1,4–H₂BDC ligand under mixed solution of DMF and H₂O. Sructural analysesind icate that complex6displays2–fold interpenetrating network of3D framework.N,N′–bis（ethylacetate）biimidazole（L） is synthesized by2,2′–biimidazole andethyl bromoacetate under low temperature and characterized by IR spectroscopyand¹H NMR spectra. The L ligand was used to synthesis a novelterbium–coordination polymer by regulating the pH value, whose molecularformula is {[Tb₃（L）（μ₃–OH）₇]·H₂O}_n（7）. In the structrue of comp lex7, throughthe μ₃–OH oxygen atoms connected into2D network structure. Furthermore, the2D structures were connected into3D supermolecule by strong hydrogen bonds.The luminescent properties of complexes1⁷were investigated at roomtemperature. The results reveal that comp lexes1³and5⁷display correspondinglanthanide ions characteristic emissions and luminescent lifetimes. Complex1emits light ye llow luminscent. Complexes2and7yie ld bright green luminescence,which is based on the characteristic transitions of Tb₃₊ions. Besides, the luminescent lifetime of comp lex2in DMSO solution is millisecond leve ls, whichind icates it has potentia l to become promising candidates for green luminescentmaterials. Complexes3and5yield yellow green fluorescent based on thecharacteristic transitions of Dy³⁺ions. Complex6emits bright red luminescent.