Syntheses, Structural Characterization And Electrochemistry Sensing Properties Of Heterometal-Containing Hetero-polyoxotungstates

Transition-metal-rare-earth（TM-RE）heterometallic polyoxometalates（POMs）have attracted more and more attention due to their complex and diverse anionic units,topological configurations as well as some special properties in catalysis,magnetism,electrochemistry and optics.We prepared a series of Cu-RE heterometallic germanotungstates by the in-situ assembly and step-by-step synthesis strategy.We also prepared a novel organic-inorganic hybrid Ag-Nd heterometallic tungstoantimonate and a series of novel organic-inorganic hybrid Fe-RE heterometallic tellurotungstates by the one-step self-assembly strategy.These compounds have been structurally characterized and their properties have been studied.This work not only provides some effective synthetic approaches for the preparations of novel heterometallic POMs,but also enriches structural types of POMs and expands the research fields of POMs.This thesis is mainly divided into the following three parts:Part Ⅰ:By the in-situ assembly-step-by-step synthesis strategy of Na₂WO₄·2H₂O,GeO_2,CuCl₂·2H₂O and 2-picolinic acid in conventional aqueous solution,four organic-inorganic hybrid 3d-4f heterometallic germanotungstates[Cu₂（H₂O）₃（PA）₃][RE_0.5Na_0.5Cu₂（H₂O）₁₁（PA）₃][α-GeW₁₂O₄₀]·8H₂O[RE=La³⁺（1）,Ce³⁺（2）]and[Cu₂（H₂O）₂（PA）₃][Cu（PA）₂][RE（H₂O）₇][α-GeW₁₂O₄₀]·7H₂O[RE=Tb³⁺（3）,Dy³⁺（4）（HPA=2-picolinic acid）have been synthesized.The 1-D chain of 1–2 is constructed from neighboring structural units connected by bridging di-copper[Cu₂（H₂O）₃（PA）₃]⁺subunits whereas in 3–4,neighboring structural units are interconnected to generate a zigzag 1-D chain by bimetallic bridging[Cu₂（H₂O）₂（PA）₃]⁺subunits,and then adjacent zigzag 1-D chains are integrated into a fascinating 2-D sheet structure by heterobimetallic bridging{Tb（H₂O）₇[Cu（PA）₂]}³⁺subunits and[Cu（PA）₂]groups.1–4 represent the first examples of plenary Keggin heterometal germanotungstates including organic 3d–4f heterometal subunits so far.The electrochemical sensing properties of 1/3@CMWCNTs-nafion/GCE electrochemical sensors towards acetaminophen detection were investigated,showing that 1/3@CMWCNTs-nafion/GCE electrochemical sensors exhibit the good sensing detection towards acetaminophen and the good stability.Part Ⅱ:By the one-step self-assembly strategy in conventional aqueous solution,flexible L-tartaric acid,Ag⁺and Nd³⁺ions were introduced simultaneously to the reaction system,we successfully synthesized an unprecedented Ag-Nd heterometallic tungstoantimonate[Nd（H₂O）₆]₃[Ag₃W_4.5O₆（H₂tar）₃（tar）₃][(W₄O₁₂)(SbW₉O₃₃)]·22H₂O（5）（H₄tar=tartaric acid）.X-ray diffraction analysis indicates that the molecular structural unit of 5 consists of a rare[(W₄O₁₂)(SbW₉O₃₃)]^9–polyoxoanion linked by three[Nd（H₂O）₆]³⁺cations,which is further surrounded by three[AgW_1.5O₂（H₂tar）（tar）]moieties,forming a highly symmetrical windmill-shaped structure.Adjacent[(W₄O₁₂)(SbW₉O₃₃)]^9–units are integrated into a fascinating 3-D porous framework by neighboring[Nd（H₂O）₆]³⁺units and[AgW_1.5O₂（H₂tar）（tar）]connectors.In addition,by the signal amplification technique of enzyme biocatalysis and hybrid chain reaction,the electrochemical detection of 5 towards hepatitis B virus tDNA molecules was also studied.Part Ⅲ:Using the strategy of one-step self-assembly strategy under hydrothermal conditions,three organic-inorganic hybrid 3d-4f heterometallic tellurotungstate derivatives[Pr（H₂O）₇]₂Na₂[Fe₄（H₂O）₂（PA）₄(B-β-TeW₉O₃₃)₂]·6H₂O（6）,Na₂{[Sm（H₂O）₇]₂[Fe₄（H₂O）₂（PA）₄(B-β-TeW₉O₃₃)₂]}₂·16H₂O（7）and K₆H₂{[Tm（H₂O）₆]₂[Fe₄W₂O₅（H₂O）₂（PA）₂（HPA）₆(B-β-TeW₉O₃₃)₂]}[Fe₄W₂O₇（H₂O）₄（HPA）₄(B-β-TeW₉O₃₃)₂]·16H₂O（8）（HPA=2-picolinic acid）have been synthesized.In 6,[Pr（H₂O）₇]³⁺ions connect HPA ligands coordinating to interior Fe1³⁺ions on adjacent[Fe₄（H₂O）₂（PA）₄(B-β-TeW₉O₃₃)₂]^8–units giving rise to the1-D chain,then HPA ligands coordinating to external Fe2³⁺ions and adjacent[Fe₄（H₂O）₂（PA）₄(B-β-TeW₉O₃₃)₂]^8–units are bridged by[Pr（H₂O）₇]³⁺ions into a 2-D layer structure.In 7,neighboring structural[Fe₄（H₂O）₂（PA）₄(B-β-TeW₉O₃₃)₂]^8–units are connected together by[Sm（H₂O）₇]³⁺ions coordinating to HPA ligands on external Fe2³⁺ions givig birth to a 1-D chain structure.However,8 is an isolated structure and its molecular units contain two kinds of non-Krebs-sandwich-type{[Tm（H₂O）₆]₂[Fe₄W₂O₅（H₂O）₂（PA）₂（HPA）₆(B-β-TeW₉O₃₃)₂]}and{[Fe₄W₂O₇（H₂O）₄（HPA）₄(B-β-TeW₉O₃₃)₂]}subunits.In addition,by the specific binding between aptamers and proteins,we used 6 as the electrode modified material and realized the electrochemical dection of 6 towords MUC1.