Hydrothermal Synthesis And Structural Chemistry Of Organic-inorganic Hybrid Vanadium Selenites

The structures and properties of the compounds are profoundly affected by the unusual stereochemical effects of the so-called lone-pair electrons in heavy p-block elements in lower oxidation states. With the effect of lone-pair, the coordination atoms of heavy p-block elements in lower oxidation states are located the same side, as can lead to reducing the structural dimension. This characteristic can be used as scissors to devise the structure. The research on composite oxides of heavy p-block elements in lower oxidation states and transition metal elements, especially the early transition metal elements, is an appealing field for their great potential practical applications in many fields, such as, catalysis, fast ion conductor, ferroelectric materials, piezoelectric materials, optics materials and so on. It is significant to synthesize novel vanadium selenites, and study the rule of assemble, structure and the relation between structure and properties.We carried out the study about hydrothermal synthesis of complex oxides of vanadium selenites and intended to find the relationship between properties and structures based on summary of literature search systematically. So far we had made achievements on such aspect:Devising and synthesizing fifteen novel vanadium selenites and employing X-ray single crystal diffractometer technology to determine their structures:[V2Se2O10H2](phen)2(1); [V2SeO7](2,2'-bpy)2(2); [V4Se2O14](2,2'-bpy)4(3); {[VO(H2O)2](SeO3)}4?2H2O(4); [VO(H2O)2]2(SeO3)2[H2pipe?SO4] (5);[(V2Se4O14)2H2O][H4TETA]( 6); (NH4)2[VSe2O7]( 7); [V3Se2O11](2,2'-bpy)2(8);[V2Se2O10][H2TEDA] ?H2O(9); [(VOSeO3)2(C2O4)](H2pipe)( 10); [(VOSeO3)2(C2O4)][(1,3-pn)H2]( 11); [(VO)(SeO3)2](H2pipe)( 12);[(HSeO3)(SeO3)(VO)] ?H2O[H4TETA]0.25(13); (Se10V6FO34) ?2H2O(H2en)2.5(14); (H2en)2[Se2Mo5O21] ?2H2O(15), of which compounds 1,2,3 is discrete vanadium selenites, compounds 4,5,6,7,8 possess one-dimensional chain structures, compounds 9,10,11,12 belong to 2D structures, compounds 13,14 belong to 3D tunnel structure, and compound 15 is heteropoly acid. The effects of reaction conditions on production are considered and studied, and we found a feasible method of synthesizing vanadium selenitesThe IR spectrums, Raman of the compounds have been characterized. DSR spectrum of the 12 novel compounds have been characterized. The DSR spectrums show the compounds with unpaired electron (with V+4 atom) possess broad absorbed peaks at VIS wave range, and the compounds with only V+5 atom show a obvious absorption edge. Fluorescences of all the compounds are vanished, even if these compounds cotain phen or 2,2'-bpy molecules.The TGA was employed to characterize the thermostability of compounds 1,2,3,6,8,9,13,14. Compounds with discrete structure is better thermal stability than compounds with 2D or 3D structure. Compounds with discrete structure are thermally stable to 300℃, and compounds with 2D or3D structure are thermally stable to 200℃.DFT/BLYP calculation was carried out to study the nature of bonds and the electronic structure of compounds 1,2,5,6,9. Some conclusions can be drawn from the results, Se atom offer 4p orbit to form molecular orbit with oxygen and the 4s electrons of Te atom exists as lone-pair electron.