Synthesis, Crystal Structure And Thermochemistry Of Inorganic-organic Hybrid Borates

There are many kinds of borates. Some of them have complex structures, which provide rich resources for useful borates, especially nonlinear optic crystal materials. So the studies of the synthesis and crystal structure of borates have attracted much attention in recent years. In comparison with inorganic borates, relatively less work has been carried out on the synthesis, crystal structure and application of organic borates. In this thesis, 5 novel inorganic-organic hybrid borates have been synthesized by the reaction between boric acid and organic base under mild solvothermal and aqueous solution conditions. Their crystal structures have been determined from single-crystal X-ray diffraction data and further characterized by element analysis, FT-IR spectrum, Raman spectrum, XRD and simultaneous DTA-TG(1) Four novel inorganic-organic hybrid borates, imidazolium pentaborate [C₃H₅N₂][B₅O₆(OH)₄], 2-methylimidazolium pentaborate [C₄H₇N₂][B₅O₆(OH)₄], diethylenetriamine tetradecaborate [(C₄N₃H₁₅)₂][B₁₄O₂₀(OH)₆] and pyridine pentaborate [C₅H₆N]₂[B₅O₆(OH)₄]₂·[C₅H₅N], have been synthesized by solvothermal reaction and their crystal structures were determined from single crystal X-ray diffraction data. The results show that the molecular structures of [C₃H₅N₂][B₅O₆(OH)₄] and [C₄H₇N₂][B₅O₆(OH)₄] are similar. Both of them have an isolate pentaborate anion [B₅O₆(OH)₄]^- The molecular structure of [(C₄N₃H₁₅)₂][B₁₄O₂₀(OH)₆] contains the first example of the largest isolated ring tetradecaborate anion [B₁₄O₂₀(OH)₆]^4- in which there exists a large sixteen-member ring with internal dimensions of 7.424x5.685 A. The molecular structure of [C₅H₆N]₂[B₅O₆(OH)₄]₂·[C₅H₅N] is composed of [C₅H₆N]⁺ cations, isolated pentaborate anions [B₅O₆(OH)₄]^- and solvent [C₅H₅N] molecule. It is worth noting that some borates have been obtained under solvothermal condition with pyridine as the solvent during the preparation and no pyridine borate has been reported for its weak alkalescence. Under our experimental condition, pyridine was both a solvent and a reactant, and meanwhile formed its solvate.(2) A novel diethylenetriamine tetraborate [C₄H₁₅N₃][B₄O₅(OH)₄] have beensynthesized and characterized.(3) Two inorganic-organic hybrid borates, [C3H5N2]3[Bc>Oi2(OH)6] and [(CH2)6N4H][B5O6(OH)4]-0.5H2O have been prepared by literature method and identified by element analysis, FT-IR spectrum , Raman spectrum, XRD and simultaneous DTA-TG All the results indicate that the synthetic samples are pure and suitable for the calorimetric experiment. The molar enthalpies of solution of the synthetic samples in approximately lmolL"1 HCl(aq) have been determined by microcalorimeter, and the standard molar enthalpies of formation of [C3H5N2]3[B9O,2(OH)6] and [(Clt^HHBsCUOH^]-0.5^0 ( -(TH^ld-mor1 and -(4042.7±4.1)kJ-mor1 , respectively) have been obtained by designing thermochemical cycles.