Synthesis, Characterization And Properties Study On Organic-inorganic Hybrids Based On Aminopolycarboxylate Edta And Keggin Type Polyoxometalates

The aim of this paper is using Keggin-type polyoxometalates(POMs) as the basic building blocks to synthesize some inorganic-organic hybrid complexes with novelty structure and excellent properties, which based on main group metal, transition-metal, organic ligand EDTA and Keggin type polyoxometalates, through covalent, ionic, hydrogen boods or intermolecular and electrostatic interactions; to study the synthetic conditions, structure and properties for these hybrid complexes; in addition to analysis the relationship between structures and properties of these hybrid complexes.In this paper, five novel inorganic-organic hybrid complexes based on Keggin- type polyoxometalates have been successfully synthesized by solution method, and characterized by single-crystal X-ray diffraction(XRD), infrared spectroscopy(IR), thermogravimetric-differential thermal analysis(TG-DTA), ultraviolet visible(UV-Vis) spectroscopy, cyclic voltammetry(CV), photoluminescence(PL) and ultravioletevisible diffuse reflectance spectrum(UV-vis DRS). The thermal stabilities, photochromic properties and catalystic activities of these complexes have been studied.1. Two novel 3D multifunctional network organic-inorganic hybrid supermolecular complexes Na(Bi HEDTA�2H2O)3(PW12O40)�2H3O(1) and Na(Bi HEDTA�2H2O)3(PMo12O40)�2H3O�2H2O(2) have been successfully synthesized, which constructed from phosphotungstic acid(for 1), phosphomolybdic acid(for 2), Bi EDTA, and Na+. Complex(1) crystallized in the hexagonal system, P-3 space group with a = 17.1349(6) ?, b = 17.1349(6) ?, c = 18.1206(14) ?, ? = 90�, ? = 90�, ? = 120�, V = 4607.5(4) ?3, Z = 2, R1 = 0.0443, w R2 = 0.1417. The complex(2) crystallized trigonal system, P-3 space group with a = 17.2717(12) ?, b = 17.2717(12) ?, c = 17.751(2) ?, ? = 90�, ? = 90�, ? = 120�, V = 4585.8(7) ?3, Z = 2, R1 = 0.0336, w R2 = 0.0959. Under UV light irradiation Complex(1) and Complex(2) exhibit excellent reversible and irreversible photochromism, respectively. Moreover Complex(1) exhibits excellent photocatalytic activity in degradation of methyl orange(MO) dyes under irradiation of UV-visible light. It can be reused for at least six cycles without obvious loss of its activity in the degradation experiments. While Complex(2) shows catalytic activity in elimination of methanol. The elimination rate of methanol reaches 56.9%, when the catalyst is 0.2g, the concentration of methanol is 2.3 g�m-3 and the flow velocity is 10 m L�min-1 at 100 �C.2. Two novel 3D supermolecular organic-inorganic hybrid complexes {(Si W12O40)�[Na6(Co EDTA)2�13H2O]�2H3O�x H2O}n(3),(Co H4EDTA�H3O)(Co H2EDTA�H3O)(Si W12O40)�15H2O(4), which constructed from silicotungstic acid, Co EDTA, and/or Na+, have been successfully synthesized. Complex(3) is an 3D infinite supramolecule, which main linked through coordinate-covalent bonds with large amounts of metal ions especially the bridging roled sodium. There are six different coordination environments and two types coordination number of 5 and 6 for Na+ in Complex(3), to the best of our knowledge, this phenomenon is quite rare. Complex(4) forms supramolecule by non-covalent bonds supramolecular forces of hydrogen boods, intermolecular and electrostatic interactions. The crystal date of Complex(3): monoclinic system, P21/n space group, a = 15.4691(6) ?, b = 29.3237(13) ?, c = 16.5389(7) ?, ? = 90�, ? = 102.1600(10)�, ? = 90�, V = 7333.9(5) ?3, Z = 1, R1 = 0.0524, w R2 = 0.1415. The crystal date of Complex(4): triclinic system, P-1 space group, a = 13.0101(5) ?, b = 14.5594(6) ?, c = 19.4444(8) ?, ? = 81.734(3)�, ? = 75.230(4)�, ? = 85.989(3)�, V = 3522.3(3) ?3, Z = 1, R1 = 0.0681, w R2 = 0.1983. These complexes exhibit good catalytic activity for catalytic oxidation of methanol, when the initial concentration of methanol is 3.0 g�m-3, flow rate is 10 m L�min-1, and the quality of catalyst is 0.2 g, for Complex(3) and Complex(4) the maximum elimination rates of methanol are 85%(150 �C) and 92%(120 �C), respectively.3. A novel photochromic inorganic-organic hybrid complex {(PW12O40)�[Na2(Ni H2EDTA�H2O)(H4EDTA)�2H2O]�2H2O�H3O}n(5) has been successfully synthesized, which constructed from phosphotungstic acic, EDTA, Ni2+ and Na+. It crystallized triclinic system, P-1 space group with a = 13.011(3) ?, b = 13.215(3) ?, c = 20.392(4) ?, ? = 95.96(3)�, ? = 102.84(3)�, ? = 105.18(3)�, V=3249.9 ?3, Z=1, R1 = 0.0380, w R2 = 0.0809. Under UV or visible light irradiation, Complex(5) plays excellent optical property of a fast-responsive reversible photochromism. The coloration-decoloration process is redox reaction of W(?)- W(?), which can be repeated at least 25 times, showing a long-life and excellent reversible photochromism. The photochromic property of Complex(5) also has been investigated by techniques of UV-vis DRS and PL.