Hydrothermal Synthesis, Crystal Structures And Properties Of Inorganic-Organic Hybrid Materials Based On Polyoxometalate

Polyoxometalates-organic hybrid materials as a kind of multifunctional material are widely studied for their interesting applications in catalysis, electronic conductivity, magnetism, nonlinear optical properties and medicine. The research on this kind of material had not only promoted the development of material science by the synthesis of new species, but also the development of chemistry by combining molecular engineering science, organic chemistry and solid inorganic chemistry together. And more, it will become a new power to push on the creation of new branch of the chemistry.In this paper, novel molybdophosphates and tungstophosphates inorganic-organic hybrid materials have been hydrothermally synthesized by using organic amines as templates under different conditions. Structures and properties of these complexes have been determined by single crystal X-ray diffraction and ICP, CHN, IR,TG-DSC, CV, UV-Vis. The main results are as follows:In the phosphomolybdates system, two layered molybdophosphates have been obtained. The synthesis conditions including pH and concentration of the solution, temperature and time of reaction were discussed in detail. It was found that the pH value of the reaction system is very important for the yield and the crystal quality of the product. The species of the organic amines are crucial and different kind of organic amines can lead to different structure. Structure analysis suggests that [P2Mo₅O₂3]⁶- anions contain five MoO₆ octahedra and two PO₄ tetrahedra, Mo, P atoms show a distorted pentagonal bipyramidal configuration. In compound (H₃dien)₂P₂Mo₅O₂3, anion clusters and protonated dien are connected to an infinite planar structure by hydrogen bonds; protonated amines occupy the interlayer of the framework and balanced the charge of the framework. The thermal decomposition kinetics of (H₃dien)₂P₂Mo₅O₂3 has been investigated through non-isothermal TG-DSC. The results show that the decomposition process of (H₃dien)₂P₂Mo₅O₂3 is undergo two stages. The most probable kinetic function is Avrami-Erofeev Equation (n=3/4), and the corresponding mechanism is controlled by random nuclear producingand growing process. The apparent activation energy (Eo) and the pre-exponential constant (A) are 162.79 kj-mol"1 and 1.7X1014S'! respectively. The complex {[Cu(phen)2][Cu(phen)(H2O)]2P2Mo5O23}-9H2O was a double one-dimensional zigzag chain molybdophosphate. Adjacent chains of this complexes are stably packed together to form an interesting inorganic-organic hybrid material through n-n stacking interactions between phen groups.By changing the organic temple, we obtained a porous compound {[Cu(en)-(Hen)]2P2Mo5O23}'3H2O. Single crystal analysis showed that the porous structure was constructed [P2MO5O23]6" and [Cu(en)(Hen)]3+ cationic units through Mo-O-Cu-P links.In the tungstophosphate system, four novel crystals with different structure have been synthesized under hydrothermal reaction system. The compound (dienH3)2P2WsO2362)-4H2O, the crystal structure indicates that the straight channels structure from the heteropoly anions and [Cu(2,2' -bipy)2]2+ cationic units throughW-Od-Cu-0-P- O-Cu-Od-W links. In the complex {[Cu(en)2]6(PWi204o)2}-6H20, the most remarkable structural feature was that polyoxoanions [PW12O40] " were linked to each other through u -oxygen.Both complexes [Cu(phen)2]3(PWi204o)2-3H20 and [Cu(phen)2]3 (PMoi204o)2-3H2O are bimetallic cluster complexes which are composed of Keggin [PM12O40]3" (M = W, Mo) cluster attached [Cu(phen)2] coordination groups through coordination bonds and hydrogen bonds. These complexes have a reversible photochromic property. A possible photochromic mechanism was proposed based on the UV-Vis spectra of colour-changed samples.