| In this paper,nineteen polyoxometalate?POM?-based complexes containing bis-imidazole-bis-amide ligands were prepared under hydrothermal or solvothermal conditions.The compositions,structures and thermal stabilitives of the target complexes were characterized by FT-IR spectra?IR?,Single-crystal X-ray diffraction analysis?X-ray?,Powder X-ray diffraction?PXRD?and thermogravimetric analyses?TGA?.The adsorption activities for organic dyes and electrocatalytic properties of the complexes were investigated here.1.The using of 1,3-bis?1H-imidazole-4-carboxamido?-m-phenylene as an organic ligand in the presence of Co2+ion and different types of POMs,gave eight POM-based complexes?1-8?by changing the pH values and solvents.[Co?L1??H2O?2][?-Mo8O26]0.5?1?{[Co2?L1?2?H2O?3][Mo7O23]}·3H2O?2?[Co2?L1?3][?-Mo8O26]0.5[?-Mo8O26]0.5·10H2O?3?[Co2?L1?3][H4Mo8O28]·4DMA·2H2O?4?[Co2?L1?3][Si W12O40]·17H2O?5?[Co2?L1?2?H2O?4][Si W12O40]·2EtOH·2H2O?6?[Co2?L1?3][Si W12O40]·9DMA·6H2O?7?[Co2?L1?3][Si W12O40]·3DMF·6H2O?8?L1=1,3-bis?1H-imidazole-4-carboxamido?-m-phenylene,DMA=N,N'-dimethylacetamide,DMF=N,N'-dimethylformamideEtOH=ethylalcoholCompounds 1 and 2 were obtained under hydrothermal condition,and the different pH values results in two kinds of POM anions,[?-Mo8O26]4-in 1,[Mo14O46]8-in 2,as well as two similar metal–organic chains[Co?L1??H2O?2]2+or[Co2?L1?2?H2O?3]4+,respectively.Compounds 3 and 4 were synthesized under mixed-solvent conditions.There are two kinds of octamolybdate isomers,[?-Mo8O26]4-and[?-Mo8O26]4-anions in 3,but only[Mo8O28]8-anion in 4,besides a similar metal–organic cage[Co2?L1?3]4+.Complexes 1–4 structures analysis reveal that the pH values and different solvents play key roles in tuning the diverse architectures of POM anions and metal–organic motifs.Complexes 5–8 were synthesized by changing the solvents in the presence of the Co2+ion,L1 ligand and[SiW12O40]4-.The structural analysis reveals that there are two kinds of different metal-organic motifs in 5-8,namely,metal-organic cationic cage[Co2?L1?3]4+formed in the presence of H2O for 5,DMA/H2O for 7,DMF/H2O for 8,a metal-organic cationic circle[Co2?L1?2]4+constructed in the presence of EtOH/H2O for 6.That is to say,the solvents show key roles in tuning the architectures of metal-organic fragments.Furthermore,the adsorption properties of 1–8 for different organic dyes,the electrocatalytic properties for hydrogen peroxide?H2O2?and ascorbic acid?AA?of complexes 1–4,were also investigated here.2.Thecombinationof1,2/1,4-bis?1H-imidazole-4-carboxamido?-o/p-phenylene,Co2+/Ni2+ion and different types of POMs,offered seven POM-based complexes by changing the pH values and solvents?9-15?.{[Co?L2??H2O?[?-Mo8O26]0.5]}·H2O?9?[Co2?L2?2?H2O?4][?-Mo8O26]·4DMF·2H2O?10?H2[Co?L2?2?H2O?2][SiW12O40]·6H2O?11?H2[Co?L2?2?H2O?2][SiW12O40]·2EtOH·H2O?12?[Ni2?L2?2??2-OH?[CrMo6?OH?6O18]?H2O?]·H2O?13?[Co2?L3?2?H2O?4][L3][SiW12O40]·9H2O?14?[Co?L3?2?H2O?2][PWVW11VIO39]·7H2O?15?L2=1,2-bis?1H-imidazole-4-carboxamido?-o-phenyleneL3=1,4-bis?1H-imidazole-4-carboxamido?-p-phenyleneIn the structures of 9 and 10,the L2 ligands coordinate with Co2+ions to form a cationic binuclear circle[Co2?L2?2]4+in the presence of[?-Mo8O26]4-anions under hydrothermal/solvothermal conditions.Replacing[?-Mo8O26]4-with Keggin-type[SiW12O40]4-anion,it is a cationic mononuclear segment[Co?L2?2]2+in 11 and 12.When the[Cr Mo6?OH?6O18]3-anion was used,a binuclear circle[Ni2?L2?2]4+was resulted in 13.Complex 14 was synthesized in the presence of Co/L3/[SiW12O40]4-under hydrothermal conditions,which contains metal–organic chains[Co2?L3?2]n4n+.But,replacing[SiW12O40]4-with[PW12O40]3-anion,a 1D POM chain was formed in 15.The adsorption properties of 9–12 for different organic dyes and the electrocatalytic properties of 13–15 have also been investigated.3.The self-assembly of the flexible bis-imidazolyl-bis-amide?L4?ligand,?NH4?6Mo7O24·4H2O and different metal ions,provided four POMs-based complexes?16-19?.[Co?L4??H2O?][?-Mo8O26]0.5·4H2O?16?[Co?L4??H2O?2][?-Mo8O26]0.5·3H2O?17?[Ni?L4??H2O?][?-Mo8O26]0.5·5H2O?18?[Ag2?L4?2][Mo13O40]·3H2O?19?L4=N,N'-bis?1H-imidazole-4-carboxamido?-1,2-ethaneThere exist different kinds of POM anions in these structures,the[?-Mo8O26]4-,[?-Mo8O26]4-,[?-Mo8O26]4-and[Mo13O40]2-anions in 16,17,18 and19,respectively.All these complexes were extended into 2D supramolecular structure via hydrogen bonds.The results reveal that the metal ions and solvents play key roles in tuning the diverse architectures of polyoxomolybdates.In addition,the electrochemical and electrocatalytic properties of complexes 18 and19 were investigated. |
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