Syntheses,Structures And Properties Of Selenotungstates Controlled By Organic Ligands

In this dissertation,we adopted the one-step self-assembly synthesis method in aqueous solution,SeIV heteroatom salt with lone pair electrons effect reacted with sodium tungstate and rare earth ions in the presence of several diverse organic ligands,fortunately,three series of novel organic–inorganic hybrid selenotungstoates were successfully prepared through exploring the optimal reaction conditions.Not only the composition and structure of these compounds have been analyzed by us,but also the properties have been studied in detail.This work not only opens up a new perspective of the synthesis of innovative organic-inorganic hybrid polyoxometalates controlled by organic ligands,but also broadens the research on the properties of polyoxometalates.This dissertation is systematically divided into three sections to describe my work:In the first section,four selenotungstates Na16H6[Pr8(2,5-HPDC)2(2,5-H2PDC)(H2O)18 W4Se2O10(SeW9O33)2(SeW8O31)4]·181H2O [RE = La3+(1),Pr3+(2),Nd3+(3)] and Na20H4[Eu8(2,5-HPDC)2(2,5-H2PDC)(Ac)2(H2O)16W4Se2O10(SeW9O33)2(SeW8O31)4]·157H2O(4)[2,5-HPDC = pyrazine-2,5-dicarboxylic acid,Ac = Acetic Acid] decorated by pyrazine-2,5-dicarboxylic acid were successfully synthesized.1–4 were all synthesized by simple materials in aqueous solution,Na2WO4·2H2O and Na2 Se O3 were used to construct basic building blocks at first,then 2,5-HPDC or acetic acid and 2,5-HPDC were added simultaneously.Single crystal X-ray diffraction shows that the hexameric polyoxoanions of 1–3 are constructed from two trimeric {[RE4(2,5-HPDC)(H2O)9W2SeO5(SeW9O33)(SeW8O31)2]}4– segments bridged by 2,5-HPDC,in the {[RE4(2,5-HPDC)(H2O)9W2SeO5(SeW9O33)(SeW8O31)2]}4– unit,two tetravacant Keggin [SeW8O31]10– fragments and a trivacant Keggin [SeW9O33]8– fragment are connected by the {W2SeO5(2,5-HPDC)RE2(H2O)9}22+ segment.What deserve to be attention is the organic–inorganic hybrid Se-W-RE-2,5-HPDC heterometallic cluster formed by selenium heteroatoms,tungsten centers,rare earth ions and 2,5-HPDC plays an important role in the formation and stability of the structure.Furthermore,it is worth noting that adjacent polyoxoanions are connected by coordination of RE3+ with a carboxyl oxygen atom and a nitrogen atom of the nitrogen heterocyclic ring of the 2,5-HPDC to construct a stable 2-D structure.However,the hexameric polyoxoanion of 4 constructed from two trimeric {[Eu4(2,5-HPDC)(Ac)(H2O)9W2SeO5(Se W9O33)(Se W8O31)2]} segments linked by 2,5-HPDC,in the {[Eu4(2,5-HPDC)(Ac)(H2O)9W2SeO5(SeW9O33)(SeW8O31)2]} fragment,a trivacant Keggin [SeW9O33]8– moiety and a tetravacant Keggin [SeW8O31]10– segment decorated by a Eu3+ ion and a tetravacant Keggin [SeW8O31]10– decorated by {Eu(H2O)3(2,5-HPDC)}3+ were linked by {W2SeO5(AC)RE2(H2O)7}22+,what’s more attractive is the first case of high nuclear rare earth ions embedded selenotungstate decorated with both carboxylic acid ligands and rigid ligands 2,5-HPDC,in addition,organic ligands and rare-earth ions play a vital role in the formation of 4,and adjacent polyoxoanions are linked by coordination of Eu3+and two carboxyl oxygen atoms of 2,5-HPDC to form a stable 2-D structure.The electrochemical properties of the electrode material based on 2 exhibit excellent performance for the sense of paracetamol.In the second section,based on the synthesis of selenotungstoates decorated by organic carboxylic acid ligands,in order to obtain more attractive structure,organic metals and organic ligands were introduced into the reaction system simultaneously,and the concentration of the reaction solution were regulated,fortunately,we have actually succeeded in obtaining two novel decorated by both organotin and and organic ligands selenotungstoates [H2N(CH3)2]Na H4{[Sn(CH3)2]5(SeO3)2[Se2W14O52]}·17H2O(5)and [H2N(CH3)2]12[Na2(H2O)8]4H4{(SeO3)2[Sn(CH3)2]5[Se2W14O52]}4·103H2O(6).Both were synthesized by reaction of simple materials Na2WO4·2H2O,Na2 Se O3,dimethylamine hydrochloride,organotin groups,RE(NO3)3·6H2O and D-tartaric acid in acidic aqueous media.What’s interesting is that adjacent polyoxoanions of 5 are connected by organotin and Se atoms to creat the 2-D layer,more interestingly,adjacent polyoxoanions of 6 are linked by organotin and Se atoms to generate the 2-D layer firstly,and then neighouring 2-D layers are interconnected to form a 3-D dimensional framework through {Na4(H2O)8} clusters.5 and 6 represent the first multi-dimensional organotin containing selenotungstates,which provides us with a great exploration space for the synthesis of selenotungstates with intriguing structures.The electrochemical properties of 6 for the detection of dopamine was studied by us.In the third section,four unprecedented organic–inorganic hybrid Fe–RE–W–squaric-acid heterometallic cluster containing selenotungstates [NH2(CH3)2]7Na8[RE4Fe3W6(H2O)12(H2C4O4)4O16(SeO3)4(Se W9O33)4]·86H2O [RE = Tb+(7),Dy3+(8),Ho3+(9),Er3+(10)] have been synthesized by the one step self-assembly reaction of Na2WO4·2H2O,D-tartaric acid,3,4-Pyridinedicarboxylic acid,Na2SeO3,dimethylamine hydrochloride and RE(NO3)3·6H2O in the presence of(NH4)2Fe(SO4)2·6H2O in acidic aqueous solution.Single-crystal X-ray diffraction studies reveal that 7–10 are isostructural and their tetrameric polyoxoanions {[RE4Fe3W6(H2O)12(H2C4O4)4O16(SeO3)4(SeW9O33)4]}15– are formed by four trivacant Keggin [SeW9O33]8– fragments connected by a high-nuclear Fe–RE–W–squaric-acid heterometallic cluster {RE4Fe3W6(H2O)12(H2C4O4)4O16(SeO3)4}57+.