Syntheses,Structures And Properties Of Carboxylate-controlling Dawson-type Lanthanide-substituted Phosphotungstates

In this dissertation,based on the principle of molecular design and self-assembly,we have synthesized thirteen novel organic–inorganic hybrid carboxylated rare-earth-substituted monolacunary Dawson-type phosphotungstates by reaction of K₁₂[H₂P₂W₁₂O₄₈]·24H₂O({P₂W₁₂}),rare-earth ions,organoamine components and carboxylic acid ligands under hydrothermal conditions.All the compounds have been characterized by IR spectra,elemental analyses,X-ray single-crystal diffraction and thermogravimatric analyses.Magnetic and photoluminescence properties of some carboxylated rare-earth-substituted monolacunary Dawson-type phosphotungstates have been studied.The introduction of different carboxylic acid ligands?2-picolinic acid or oxalate?has led to the formation of different rare-earth substituted Dawson-type phosphotungstates,which indicates that carboxylic acid ligands play an importantly tunable role in the structural construction of rare-earth substituted Dawson-type phosphotungstates.This dissertation can be divided into four sections to introduce my work during the master study:Section ?.The main developments of Dawson-type polyoxotungstates and their derivatives have mainly been summarized.Section ?.The related physical measurements and reagents have been given.Section ?.Eight novel rare-earth-substituted monolacunary Dawson-type phosphotungstates decorated by 2-picolinic acid have been synthesized:[Hdap]₄[Gd?H₂O??Hpic?₃][Gd?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?1?[Hdap]₄[Tb?H₂O??Hpic?₃][Tb?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?2?[Hdap]₄[Dy?H₂O??Hpic?₃][Dy?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?3?[Hdap]₄[Ho?H₂O??Hpic?₃][Ho?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?4?[Hdap]₄[Er?H₂O??Hpic?₃][Er?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?5?[Hdap]₄[Tm?H₂O??Hpic?₃][Tm?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?6?[Hdap]₄[Yb?H₂O??Hpic?₃][Yb?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?7?[Hdap]₄[Y?H₂O??Hpic?₃][Y?Hpic?₂(?₂-P₂W₁₇O₆₁)]·21H₂O?8?Compounds 1–8 were made by reaction of the{P₂W₁₂}precursor,rare-earth ions,2-picolinic acid and1,2-diaminopropane at the pH region of 5–6 under hydrothermal conditions.Their polyoxoanionic framework{[RE?H₂O??Hpic?₃][RE?Hpic?₂(?₂-P₂W₁₇O₆₁)]}^4-can be considered that a dual-Hpic decorated[RE1?Hpic?₂]³⁺cation is embedded into the vacancy on the polar position of mono-lacunary[?₂-P₂W₁₇O₆₁]^10-fragment and a tri-Hpic decorated[RE₂?H₂O??Hpic?₃]³⁺cation grafts to the equatorial position of[?₂-P₂W₁₇O₆₁]^10-fragment through a W–O–RE linker.Each RE³⁺ion is combined with the N and O atoms on the Hpic ligands in the five-membered ring fashion and adopts the eight-coordinate highly distorted square antiprism geometry.The solid-state UV–Vis photoluminescence properties for 2,3,5 and the solid-state NIR photoluminescence properties for 5 and 7 have been studied at room temperature,and their emission spectra mainly reveal the characteristic emission bands of Tb³⁺,Dy³⁺,Er³⁺and Yb³⁺ions.Additionally,the results of magnetic susceptibility measurements demonstrate that 3 displays the single-molecule magnet behavior.Section ?.Five unique oxalate-bridging rare-earth-substituted monolacunary Dawson-type phosphotungstate dimers have been prepared under hydrothermal conditions:[H₂dap]8[Ho₂?H₂ox?₂?ox?(?₂-P₂W₁₇O₆₁)₂]·25H₂O?9?[H₂dap]8[Er₂?H₂ox?₂?ox?(?₂-P₂W₁₇O₆₁)₂]·25H₂O?10?[H₂dap]8[Tm₂?H₂ox?₂?ox?(?₂-P₂W₁₇O₆₁)₂]·25H₂O?11?[H₂dap]8[Yb₂?H₂ox?₂?ox?(?₂-P₂W₁₇O₆₁)₂]·25H₂O?12?[H₂dap]₈[Y₂?H₂ox?₂?ox?(?₂-P₂W₁₇O₆₁)₂]·25H₂O?13?9–13 are isostructural and their polyoxoanionic skeleton[RE₂?H₂ox?₂?ox?(?₂-P₂W₁₇O₆₁)₂]^16-is constructed from two[RE?H₂ox?(?₂-P₂W₁₇O₆₁)]^7-subunits through an oxalate bridge.Every[RE?H₂ox?(?₂-P₂W₁₇O₆₁)]^7-subunit can be viewed that a[RE?H₂ox?]³⁺cation is encapsulate into the vacancy of a[?₂-P₂W₁₇O₆₁]^10-fragment.Magnetic susceptibility properties for 9 and 10 have been studied and both show the antiferromagnetic interactions between adjacent rare-earth ions.Moreover,the solid-state UV–Vis and NIR photoluminescence properties for 10,12 and Yb³⁺–Er³⁺codoped samples have been investigated and their emission spectra reveal the characteristic emission bands of rare earth ions.In addition,the doping ratio of Yb³⁺/Er³⁺can control the emission intensity and emission color of Yb³⁺–Er³⁺codoped samples.