Synthesis And Characterization Of The Novel Metal Phosphite

Inorganic microporous crystal materials have not only the potential applicationsin catalysis, ion exchange, absorption, molecular recognization, ion conductor,magnetic field, but also have great significance in crystallography and the study ofbiomineralization.For the past decades, people have been interested in synthesis and applicationof transition metal phosphate with open framework. And as we know, thestructure of HPO32-is similar to that of [PO4]3-, so [HPO3]2-may act as thestructure unit to build the open framework. Compared with the research ontransition metal phosphate with open framework, the research on transition metalphosphite templated by organic amine is rare. So, in the past few years, peoplehave been interested in the research on transition metal phosphite. Up to now, alot of phosphite compounds with open framework have been synthesized, such asvanadium phosphite, chromium phosphite, manganese phosphite, iron phosphite,cobalt phosphite and zinc phosphite.Up to now, transition metal phosphites play an important role among metalphosphite. A number of transition phosphites have been synthesized, however,main block mental phosphite is few up to now.(1) Using metal iron as source materials, and triethylamine as structure-directing agent, we prepared two three-dimensional iron phosphites(H3O)2·[FeII5(HPO3)6], and NH4·[FeII2FeШ(HPO3)4] by hydrothermal treatment,which have been synthesized and characterized by single crystal X-ray diffraction.Both compounds exist six-membered channels along the c axis.The Fe centers inboth frameworks adopt slightly distorted octahedral coordination geometry andare bridged by the pseudo-pyramidal phosphates to constructe the 3D frameworks.Magnetic measurements indicate the anti-ferromagnetic interactions in thesecompounds. Otherwise, after discussing the syntheses of these novel compounds,we find that pH,reactant and temperatureare very important effect factors for thesynthesis of transition metal phosphite crystals.(2) The hydrothermal reactions of gallium oxide, phosphite, ethyldiamine andwater yield 3D network Ga2(OH)(OH2)(HPO3)3·0.5 [C2H10N2] . And structuralinvestigation suggests that the framework of the compound is built up from thelinkage of GaO6 octahedra and [HPO3]2-pseudo-pyramid unit by sharing thevertices and forming a 3D open-framework containing3-, 4-,5-and 8-memberedrings.Through a lot of experiment, we find that the following influencing factorsplayed important roles: (1) the rate of reactants mixture: the rate of reactantsmixture, especially the rate of phosphite and organic amine could play a importantpart through the adjusted of pH. (2) The effect of mineralizer: we find thatmineralizer still plays an important role in synthesizing zinc phosphite. (3) Theuse of phosphite: In general, phosphite should be enough, for its reductiveproperty lest it is oxidated to be [PO4]3-. The temperature also should be low forthe reason. In addition, there are some differences between the solid and solutionphosphite in the effects of the hydrothermal reactions should be noticed. And thismay give a direction to synthesize other metal phosphite.In summary, it is possible to replace [PO4]3-of tetrahedron configuration with[HPO3]2-of pseudo pyramid through hydrothermal synthesis to prepare structuralcomplex open-framework metalloophosphites possessing cavity size.