| In this paper,sixteen new transition metal-organic complexes?MOCs?based on Anderson-type polyoxometalate?POM?/octamolybdates building blocksandrigidpyridyl-bis?triazole?,pyridyl-triazole-tetrazole,pyrazin-bis?triazole?and pyrazin-triazole-tetrazole ligands have been successfully synthesized under the hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction,powder X-ray diffraction?PXRD?and IR spectra.The adsorption behaviors for organic dyes and electrochemical properties of the title POM-based MOCs were investigated in detail.1.The pyridyl-bis?triazole?was used as organic ligand to assemble with Anderson-type polyanions,octamolybdates and different transition metal ions under hydrothermal conditions.As a result,seven new MOCs have been successfully synthesized.It should be noted that the[CrMo6?OH?6O18]3-anions were in-situ transformed to[?-Mo8O26]4-(?-Mo8O26)anions at pH=5.8in 3.However,in 4 and 5,the?-Mo8O266 was constructed from the?NH4?6Mo7O24·4H2O.H{Co2?Hpyttz-??2?H2O?6[CrMo6?OH?6O18]}·8H2O?1?{Co2?H2pyttz-??2?H2O?4[TeMo6O24]}[Co?H2O?6]·3H2O?2?{Co3?Hpyttz-??2?H2O?6[?-Mo8O26]}·10H2O?3?{Ni3?Hpyttz-??2?H2O?6[?-Mo8O26]}·10H2O?4?{Cu3?Hpyttz-??2[?-Mo8O26]?H2O?6}·8H2O?5?{Ni3?Hpyttz-??2?H2O?8[?-Mo8O26]}·10H2O?6?{Co3?Hpyttz-??2[?-Mo8O26]?H2O?8}·2H2O?7?[H2pyttz-?=3-?pyrid-2-yl?-5-?1H-1,2,4-triazol-3-yl?-1,2,4-triazolyl,H2pyttz-?=3-?pyrid-3-yl?-5-?1H-1,2,4-triazol-3-yl?-1,2,4-triazolyl,H2pyttz-?=I3-?pyrid-4-yl?-5-?1H-1,2,4-triazol-3-yl?-1,2,4-triazolyl].Complex 1 is a two-dimensional?2D?supramolecular network based on the binuclear cobalt complex unit:[Co2?Hpyttz-??2?H2O?6[CrMo6?OH?6O18]].Complex 2 is a 1D supramolecular chain derived from the binuclear cobalt complex:{Co2?H2pyttz-??2?H2O?4[TeMo6O24]}2-,the discrete[Co?H2O?6]2+units act as counter cations.Complexes 3,4 and 5 are isostructural with different center metals?M=Co,Ni or Cu?.The adjacent 1D M-?-Mo8O26inorganic chains are linked together by the 1D metal-organic M-?Hpyttz-??chains to form a 3D framework.In complexes 6 and 7,?-Mo8O264-anions are bridged by the Ni ? ions to give a 1D Ni-?-Mo8O266 inorganic chain,the adjacent 1D Ni-?-Mo8O26 chains are connected through[Ni?Hpyttz-??2]units to form a 2D layer.The POM anions type and the coordination site of rigid pridyl-bis?triazole?ligands show great effect on the final structures.Complexes 1,2 and 6 exhibit excellent bifunctional electrocatalytic activities toward the reduction of bromate/hydrogen peroxide and the oxidation of ascorbic acid?AA?.In addition,the redox potentials of complexes 1,2 and 6 are highly sensitive to pH and may be used as a kind of potential pH sensor.2.The classical octamolybdate and Anderson type POM anions were used as inorganic building blocks to assemble with cobalt/nickel ion and pyridine-triazole-tetrazole ligand under hydrothermal conditions,resulting in six metal-organic complexes.{Co4?Htyptz-??2[TeMo6O24]?H2O?12}·4H2O?8?{Co3?Htyptz-??2[?-Mo8O26]?H2O?6}·4H2O?9?{Ni3?Htyptz?-?)2[?-Mo8O26]?H2O?8}·4H2O?10?H2{Co3?Htyptz-??2[TeMo6O24]?H2O?8}·6H2O?11?{Ni3?H2typtz-??2[TeMo6O24]?H2O?8}·6H2O?12?{Co3?H2typtz-??2[TeMo6O24]?H2O?8}·6H2O?13?[H2typtz-?=3-?tetrazol-5-yl?-5-?pyridin-2-yl?-1,2,4-triazolyl),H2typtz-?=3-?tetrazol-5-yl?-5-?pyridin-3-yl?-1,2,4-triazolyl),H2typtz-?=3-?tetrazol-5-yl?-5-?pyridin-4-yl?-1,2,4-triazolyl)].In complex 8,the TeMo6 anions acting as the inorganic bridging ligand provide four terminal oxygen atoms to link the[Ni?Hpyttz-??2]units,constructing a 2D layer.Complex 9 shows a 3D?-Mo8O26-based framework with two kinds of 1D chains.Complex 10 is a 2D network,which is constructed from different organic and inorganic chains.Complexes 11,12and 13 are isostructural.In complexes 11,12 and 13,the TeMo6 anions acting as the inorganic bridging ligands link the 1D Co-Htyptz chain to construct a2D layer.The metal ion,the substituent site and the coordination mode of the ligand and the type of POMs have a great influence on the structures of the complexes.The complexes 9 and 11 exhibit electrocatalytic activities toward the reduction of nitrite and bromate,and the electrochemical behavior of the9-/11-bulk-modified carbon paste electrode is pH dependent,may be used as a kind of potential pH sensor.The complexes 9-12 exhibited excellent adsorption activities for the cationic dyes methylene blue?MB?and neutral red?NR?.In addition,9 and 11 exhibited rapid adsorption activity against gentian violet?GV?.3.By introducing the pyrazin-bis?triazole?and pyrazin-triazole-tetrazole ligands into Anderson-type POM-transition metal systems,three new POMs-based MOCs have been successfully synthesized under hydrothermal conditions.{Co2?H2pytty?2[CrMo6?OH?5O19]?H2O?8}·10H2O?14?{Co5?pytty?2[TeMo6O24]?H2O?16}·6H2O?15?{Cu2?H2pytytz?2[AlMo6?OH?5O19]?H2O?8}·10H2O?16?[H2pytty=3-?pyrazin-2-yl?-5-?1H-1,2,4-triazol-3-yl?-1,2,4-triazolyl),H2pytytz=3-?tetrazol-5-yl?-5-?pyrazin-2-yl?-1,2,4-triazole].Complex 14 is a 0D structure containing a cation[Co2?H2pytty?2]4+and an isolated B-type[CrMo6?OH?5O19]4-anion.Complex 15 is 2D layer formed by A-type[TeMo6O24]6-anion and two kinds of 1D chains.Complex 16 is a1D chain,which is constructed form a[Cu2)Hpyttz-?)2]unit linking two[AlMo6?OH?6O18]3-anions.The structures of these complexes are influenced by the type and various coordination modes of the POMs.Complexes 14 and 15 shows bifunctional electrocatalytic properties in the reduction process of H2O2 and nitrite,as well as in the oxidation process of AA. |
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