Molecular Design, Hydrothermal Synthesis And Characterization Of Organic-inorganic Hybrids Based On Polyoxometalate Cluster Building Block

In this paper, nine new organic-inorganic hybrid compounds based on pre-preparedKeggin clusters have been synthesized by utilizing various organic chelating or bridgingN-donor ligands. In addition, by using {Mo8O26} as building block, a new 1D chainlikecompound has been prepared. All these compounds have been structurally characterizedby elemental analyses, IR, EPR, XPS, TG and X-ray single crystal diffractions. The rolesof the first nine compounds under hydrothermal conditions and the factors influencing thestructures of these compounds have also been studied.1. Seven new organic-inorganic hybrid compounds have been prepared by usingKeggin clusters as building blocks and introducing complex fragments{MxLy} (M =transition metal ions, L = chelating ligands):{[Co(phen)2]2[SiMoVI8MoV4O40(VIVO)2]}·H2O 1{[Co(phen)2]2[PMo12O40(VO)2]}{[Co(phen)2(OH)]2[PMo12O40(VO)2]}·2.5H2O 2[Cu(phen)2]2{[Cu(phen)]2[SiMo12O40(VO)2]} 3{[Zn(phen)2]2[GeMo12O40(VO)2]}{[Zn(phen)2(H2O)]2[GeMo12O40(VO)2]}·3H2O 4[M(2,2?-bpy)2(H2O)]2[SiMoVI8MoV4VIV2O42] (M = Co 5, Zn 6)[Ni(2,2?-bpy)2(H2O)]2[PMoVI7MoV5VIV2O42] 7 (phen = 1,10-phenanthroline,2,2?-bpy= 2,2?-bipyridine). From these compounds, we can conclude:(1) in such system, Keggin-type polyoxometalates with different redox propertieshave no obvious structural influences on these compounds. The structures of thesecompounds are all based on bicapped Keggin clusters.(2) The structures of these compounds are significantly different when chelatingligands with different steric possession, such as phen and 2,2?-bpy, are used. Using phen,compounds 1-4 are prepared: compound 1 is a discrete bicapped Keggin cluster,compound 2 is a 2D layer, while 3 and 4 are both bicapped multisupporting Kegginclusters. The structural difference between 1 and 2 is owing to tha amount of phen, whilethe structural differences among other compounds are ascribed to the characteristic ofmetal ions. Using 2,2?-bpy, we can only obtain three isostructural bicapped bisupportingKeggin clusters 5-7.2. Two novel organic-inorganic hybrid compounds have been synthesized by usingKeggin cluster as building blocks and 4,4?-bpy as bridging ligand:{Cu3(4,4?-bpy)3(H2O)[PMo12O40(VO)2]·5H2O 8(H2bpy)4[Si2MoVI16MoV8O80(VIVO)4]·2H2O 9Compound 8 is a 3D interpenetrating network formed by parallel interpenetration of 1Ddouble ladders. Compound 9 is a bicapped Keggin dimerized polyanion, and all4,4?-bipyridine molecules in compound 9 are completely protonated and function ascountercations.3. A novel chainlike hybrid with green fluorescent emission has been synthesized byusing {Mo8O26} as building block and introducing the chelating ligand 2,2?-bpy andbridging ligand phnz: (H3O)[Ag3(2,2?-bpy)2(phnz)2(β-Mo8O26)] (phnz = phenazine) 10.