Synthesis And Properties Of Lanthanide/Transition Metal-Dawson-type Phosphotungstates

Polyoxometalates?POMs?, as an important family of metal oxides, have been regarded as one kind of outstanding inorganic building block for the design and synthesis of inorganic-organic hybrid materials due to the coordination ability of the numerous external oxygen atoms, nanometer-sized and an unmatched range of physical and chemical properties,which have potential applications in the fields of catalysis, photochemistry, sorption, biology and medicine. One of the remarkable approaches in the design of functionalized materials based on POMs is to combine lanthanum metals with POMs, facilitating the production of new architectures with fascinating structures and modified properties, which has received much attention from chemists.In this paper, we selected Dawson-type POMs as building blocks, synthesizing 17 novel Ln-Dawson-type phosphotungstates clusters 1-17 and one 3D metal-organic framework 18 based on Dawson-type POMs and copper ions, which have been structurally characterized by IR, UV-vis, elemental analysis, XRPD and complete single crystal structure analyses.Moreover, the electrocatalysis, luminescent spectroscopy and magnetic properties have also been investigated in detail. The text has divided into two chapters which were introduced as follows:1. Four novel inorganic- organic hybric compounds 1-4 have been prepared under hydrothermal conditions by the reaction of [P₂W₁₈O₆₂]6-, pyridine-2,6-dicarboxylate?H₂pydc?and Ln?NO3?₃?Ln = Eu, Pr, Tb, Gd?.H_0.5[Eu_4.5?pydc?₄?H₂O?₂1.5(P₂W₁₈O₆₂)]·11H₂O?1?H_2.25[Pr_3.25?pydc?₃?H₂O?19(P₂W₁₈O₆₂)]·9H₂O?2?[Tb?pydc??H₂O?₃][Tb₄?pydc?₃?H₂O?19?OH?(P₂W₁₈O₆₂)]·4H₂O?3?H_0.5[Gd_4.5?pydc?₄?H₂O?₂5.5][P₂W₁₈O₆₂]·16H₂O?4?Compound 1 exhibits a ladder-type structure and red fluorescence at room temperature.Compounds 2 and 3 display sandwich-type dimer structure based on Dawson-type POMs and Ln-pydc, while 4 is constructed by the [P₂W₁₈O₆₂]6-cluster anions and Gd-pydc coordination cation units. The magnetic behavior of 2 suggests the presence of antiferro-magnetic coupling interactions between Pr metal centers, while 4 represents the ferro-magnetic coupling interactions. The optical properties indicate the energy bands?Eg? of compounds 1-4 are 3.41,3.50, 3.46 and 3.42 eV, respectively, implying that compounds 1-4 are semiconductor materials. In addition, compounds 1-4 exhibit good electrocatalytic activity toward the reduction of nitrite and hydrogen peroxide.2. Four compounds 5-8 have been synthesized by the reaction of [P₂W₁₅V₃O₆₂]9-,isophthalic acid and Ln?NO3?₃, while compound 9 has been synthesized without the present of isophthalic acid.[Ce3?H₂O?₂0(P₂W₁₅V₃O₆₂)]·13.5H₂O?5?[K1.5Pr2.5?H₂O?₂6(P₂W₁₅V₃O₆₂)]·13H₂O?6?[Sm3?H₂O?₂2(P₂W₁₅V₃O₆₂)]·14H₂O?7?[Sm3?H₂O?16(P₂W₁₅V₃O₆₂)]·8H₂O?8?[Ce3?H₂O?₂2(P₂W₁₅V₃O₆₂)]·13H₂O?9?Compouds 5, 8 and 9 display 1D zigzag chain while compounds 6 and 7 exhibit twodimensional network. The UV-vis spectra, electrical properties and magnetic properties for5-9 have been studied.Using the H₂ pydc instead of the isophthalic acid, eight compounds 10-17 have been synthesized.H[Ce4?pydc?₂?H₂O?₂4(P₂W₁₅V₃O₆₂)]·14H₂O?10?H[Pr4?pydc?₂?H₂O?₂4(P₂W₁₅V₃O₆₂)]·14.5H₂O?11?H[Nd4?pydc?₂?H₂O?₂3(P₂W₁₅V₃O₆₂)]·15H₂O?12?H[Sm4?pydc?₂?H₂O?₂3(P₂W₁₅V₃O₆₂)]·12H₂O?13?H[Gd4?pydc?₂?H₂O?₂2(P₂W₁₅V₃O₆₂)]·14H₂O?14?H[Tb₄?pydc?₂?H₂O?18(P₂W₁₅V₃O₆₂)]·8H₂O?15?H[Dy4?pydc?₂?H₂O?₂2(P₂W₁₅V₃O₆₂)]·16H₂O?16?H1.5[Eu_4.5?pydc?₃?H₂O?18(P₂W₁₅V₃O₆₂)]·18.25H₂O?17?Compounds 10-16 display sandwich-type dimer structure. The magnetic properties of10-12 and 15-16 have been studied, indicating antiferromagnetic interactions between metal atoms. Compound 17 exhibits a 3D porous structure, displaying the fluorescence emissions of Eu3+. Using dpdo instead of the isophthalic acid and introducing Cu2+, compound H3[K3Cu1.5?dpdo?5?H₂O?₂2(P₂W₁₅V₃O₆₂)]·6H₂O?18? has been obtained, in which the electrochemical behavior has been studied.