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Synthesis And Characterization Of Transition Metal Phosphates Phosphites And Phosphonates Microporous Materials

Posted on:2006-03-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y FanFull Text:PDF
GTID:1101360155453519Subject:Inorganic Chemistry
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The prospects of designing and synthesizing the compounds with microporous solids are of great interest for their potential applications in the fields of molecular sieves, ion-exchange, catalysis, and separations. As part of the renaissance in the study of open-framework metal phosphates, a series of novel compositions of inorganic frameworks with one-, two- or three-dimensions (1-D, 2-D or 3-D) have been prepared by using polar organic molecules as structural directors. However, there have been great challenges and opportunities in terms of controlling their shape and size for selective applications, because the crystallization process is manipulated by various factors, such as solvent, gel composition, type of templates, crystallization time and temperature. For the structural feature of the pyramidal [HPO32-] hydrogen phosphite group, representing a member of the phosphorus oxoanions, can make at most three links to adjacent cations via P-O-M (M = metal) bonds and provide more variety and novelty of the new materials. Since the syntheses of vanadium phophites in the presence of piperazinium cation as structural director by Zubieta et al., the great interest in the synthesis of new transition metal phosphites has been aroused. Up to date, transition metal phosphites have been extensively studied, the compounds of V(III), Fe(IH), Co(II), Mn(II), Zn(II) and Cr(III) with their various properties have been reported. Organically-templated main block metal B(II), Ga(III), In(III)phophites were also prepared. As for metal phosphonates, the pioneering work of A. Clearfield on the use of phosphonates opened the way. Some research groups, including ours, recently developed new routes for synthesizing microporous solids with accessible porosity and have reported many novel compounds.In this thesis, we described the synthesis, crystal structure and some properties of a series of metal phosphates, phosphates and phosphonates compounds. And summarized the rules of synthesis and compared the difference of structures and synthesis. Influences of other experimental factors, such as reaction temperatures, reaction times, pH values and molar ratios of the starting materials etc on the composition, the structures, purity and crystallinity of the final products'were studied.As a sequel of searching for new microporous materials we are currently exploring the synthesis of metal phosphates in solvolthermal systems and have synthesized several interesting compounds with three-dimensional structure. We discuss here the syntheses and structural features of thesecompouds. We learned and advanced a technology to improve the hydrothermal and solvothermal synthesis andget a new metal sulfate.Under mild hydrothermal conditions, using triethylamine as structure-directing agent, two three-dimensional iron phosphites (H3O)2[FeH5(HPO3)6], and NH4[FeII2Fem(HPO3)4], have been synthesized and characterized by single crystal X-ray diffraction. Both compounds form three-dimensional frameworks with six-membered channels along the c axis. The Fe centers in both frameworks adopt slightly distorted octahedral coordination geometry and are bridged by the pseudo-pyramidal phosphites. Magnetic measurements indicate the anti-ferromagnetic interactions in these compounds. We discuss here the syntheses and structural features of these novel compounds and the structural relationships among them. In addition, we find that pH, reactant and temperatureare very important effect factors for the synthesis of transition metal phosphite crystals. Afterthat we synthesized some manganese phosphates.Under mild hydrothermal conditions, a novel three-dimensional inorganic-organic hybrid compound, Mn(H2O)[HO3PCH2NH(CH2CO2)2] from a reaction of Mn (II) ion with N-(phosphonomethyl)iminodiacetic acid (H4PMIDA) was reported. The compound crystallizes in the monoclinic P2\/n. In this structure each Mn atom is six-coordinated with the carboxylic groups and phosphonic groups to form layers along the be plane. These layers are further connected with the organic moieties of H2PMIDA, resulting in a complicated three-dimensional network structure. The coordination mode of the PMIDA is different from that in another compound synthesized from PMIDA repored by A. Clearfield etc. In the compound, two carboxylate groups of H2PMIDA ligands have two coordination modes., IR spectrum and magnetic susceptibility of this compound are given. Thermogravimetric analysis indicate this compound is stable below 299 °C. The temperature dependence of magnetic susceptibility shows a weak antiferromagnetic interaction in the compound.Under mild solvothermal synthesis conditions, a cobalt phosphonate Co4(H2O)i2[O3PCH2N(CH2CO2)2]2[HO3PCH2N (CH2CO2)2]2 formed reaction of Co (II) ion with iV-(phosphonomethyl)iminodiacetic acid (H4PMIDA) was reported. The feature of the structure is three-dimensional supramolecular network builded by tetrametallic secondary building units (SBU) which were formed by HPMIDA ligands and cobalt atoms. These SBU are held together by hydrogen bonds resulting in a 2D layer. The water molecules are located between the layers, and linked the layers using hydrogen bonds forming three-dimensional supramolecular network. The temperature dependence of magnetic susceptibility shows a weak antiferromagnetic interaction in the compound. High spin metal centers are known to quench luminescence through electron transfer process. To our surprise, compound 1...
Keywords/Search Tags:Characterization
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