Assemblyand Its Properties Of Poms Based On Triazole, Imidazole And Pyrazine Derivatives And Mixed Ligands

In this paper,under the hydrothermal conditions,by using imidazole and pyrazine derivatives as organic ligands,?1,4-bis?1,2,4-triazol-1-ylmethyl?benzene?bbtz?,4-?2,5-dihydro-1H-imidazol-1-yl?benzaldehyde?L¹?and4-?2,5-dihydro-1H-imidazol-1-yl?benzoic acid?L²?,2,3-diphenyl-pyrazine?L³?,2,3-diphenyl-quinoxaline?L⁴??and tuning the p H of reaction system,varieties of POMs,temperature and so on,fifteen compounds based on Keggin,Wells-Dawson and isopolymolybdate polyoxometalate?POM?-based were synthesized.Their structures were characterized by single crystal X–ray diffraction.Furthermore,the electrochemical,photocatalytic and the fluorescence properties of these new POM-based compounds were also explored.1.Underhydrothermalconditions,byusinga1,4-bis?1,2,4-triazol-1-ylmethyl?benzene?bbtz?ligand,two compounds based on Keggin and isopolymolybdate were synthetized in one pot:[Cu₂?bbtz?₄(Si Mo₁₂O₄₀]?1?,[Cu₂?bbtz?₄(Mo₈O₂₆]_1/2·H₂O?2??bbtz=1,4-bis?1,2,4-triazol-1-ylmethyl?benzene?Single crystal structure analysis shows that in compound 1,two adjacent wave-like Cu^II-bbtz units are joined by SiMo₁₂2 anions through bbtz ligands to form a one-dimensional ladder-like chain.Two adjacent one-dimensional chains share the same Cu^III ions to form a three-dimensional framework.In compound 2,the?-Mo₈ anions and the Cu₃?bbtz?₂ clusters are alternately connected to form a one-dimensional chain structure,and one dimensional chain connects with the Cu^III to form a three-dimensional framework.2.Imidazole derivatives 4-?2,5-dihydro-1H-imidazol-1-yl?benzaldehyde?L¹?and 4-?2,5-dihydro-1H-imidazol-1-yl?benzoic acid?L²?as organic groups have strong coordination ability.The additional oxygen atoms can not only coordinate with transition metals but also act as supramolecular linker to support hydrogen bond interaction.By using these two kinds of imidazole derivatives L¹ and L² with different oxygen content as organic ligands,four Keggin-and one Wells-Dawson-based compounds were synthesized:[Ag₂L₄¹(H₂SiW₁₂O₄₀)]?3?,[Cu₂L₄¹(HPW₁₂O₄₀)]?4?,[CuL₄¹?H₂O?₂(HPMo₁₂O₄₀)]·2H₂O?5?,[Cu₂L₆¹?H₂O?(H₂P₂W₁₈O₆₂)]·2L¹?6?,[Ag₂L₄²(HPMo₁₂O₄₀)]·2L²?7?.?L¹=4-?2,5-dihydro-1H-imidazol-1-yl?benzaldehydeL²=4-?2,5-dihydro-1H-imidazol-1-yl?benzoic acid?Compounds 3 and 4 are isomorphic.Compound 3 and 4 have two symmetric AgL¹₂ or CuL¹₂ units to form a hole,with Keggin anion embedding in the hole.In compound 5,the CuL¹₄ constructs a crisscross structural unit.The adjacent structural units are connected by hydrogen bonds to form a supramolecular two-dimensional network structure,and the POM anions are embedded in the grids.The CuL¹₃ subunits in compound 6 are connected with the adjacent P₂W₁₈8 anions to form an S-type one-dimensional chain structure,which are connected by hydrogen bond to form a two-dimensional layer.In compound 7,POM anions are alternately joined with AgL²₂ subunits to form one-dimensional chain structures,and adjacent one-dimensional chains are connected to form a two-dimensional networks by the weak O…O interactions between two L².3.By using two pyrazine derivatives 2,3-diphenyl-pyrazine?L³?and2,3-diphenyl-quinoxaline?L⁴?,eightKeggin-basedcompoundswere hydrothermallysynthesizedandstructurallycharacterized.Interestingly,compounds 14 and 15 own both L³ and L⁴ ligands:[Ag₄L₅³(SiW₁₂O₄₀)]·28H₂O?8?,[Ag₃L₄³(PW₁₂O₄₀)]?9?,[Ag₃L₂³?H₂O?(PW₁₂O₄₀)]?10?,[Ag₄L₄⁴(SiW₁₂O₄₀)]?11?,[Ag₃KL₄⁴?H₂O?(SiW₁₂O₄₀)]?12?,[Ag₆L₆⁴(PMo₁₂O₄₀)₂]?13?,[Ag₄L³L₃⁴(C₁₄H₁₀O₂)(SiW₁₂O₄₀)]·8H₂O?14?,[Ag₄L₂³L₄⁴(GeMo₁₂O₄₀)]?15??L³=2,3-diphenyl-pyrazine,L⁴=2,3-diphenyl-quinoxaline?In compound 8,the linear[Ag₄L₄³]⁴⁺subunits link SiW₁₂2 anions to form a chain.Adjacent two chains connect each other through Ag-O bonds and a screwy-like double track is built.Compound 9 owns 1D leaf-like Ag^I-L³ chains,which are further linked by anions to build a 2D grid-like layer.Compound 10 was obtained under the same conditions with 9,except for different temperature.In 10,the inorganic double chains are connected by linear metal-organic clusters[Ag₃L₂³]³⁺and a 2D layer is formed.Compounds 11 and 12 were also obtained at different temperatures.In 11,the adjacent grid-like layers share the same Ag ions to construct a 3D framework.Compound 12 owns 1D cycle-connecting-cycle chains,which are further linked by anions and Ag ions to build a 3D structure.Compound 13 is a 3D framework,with dissociative anions accommodated in it.Compounds 14 and 15 own mixed organic ligands L³ and L⁴.Compound 14 own two kinds of chains,which are linked by anions to form a“ladder”.Compound 15contains discrete anions and[Ag₂L³L₂⁴]²⁺units.