Exploring Synthesis And Characterizations Of Borates Under Hydro/Solvothermal Conditions

Borates have attracted considerable interests in recent years, due to their novel structures and applications in mineralogy, nonlinear optical materials and laser materials. Generally, the B atom is coordinated by O atoms not only in three fold(triangular, BO3) but also in four fold coordinations(tetrahedral, BO4). These triangular or tetrahedral groups can be further connected to each other through common vertices to build different isolated oxoboron clusters, which can be used as the structural building units(SBUs) to further polymerize into infinite chains, sheets,and frameworks. Four series of borates were synthesized in this paper:main group metal borates, transition metal complexes borates, alkali-alkaline earth metal borates,other metal borates and inorganic-organic hybrid borates. The structures of these new crystals were determined by the single crystal x-ray diffraction and were also characterized by x-ray powder diffraction, infrared spectroscopy, ultraviolet spectroscopy and thermos-gravimetric analyzer. We also tested the SHG efficiency of acentric structure crystals.The first chapter is the literature review, which introduces the research progress of transition metal borates, alkali-alkaline earth metal borates, main group metal borates, and inorganic-organic hybrid nonmetal borates.The second chapter introduces the synthetic methods, experimental materials and experimental apparatus.The third chapter describes four new aluminoborates templated by transition metal complexes, which are synthesized under hydrothermal or solvothermal conditions : [Cd(en)(dap)][Al B5O10](3–1), [Cd2(en)3H2O][Al2B10O20]·H2O(3–2),[Zn(en)(dien)][Al B5O10](3–3) and [Zn(en)2][Al B5O10](3–4)(en=ethylenediamine,dap=1,3-diaminopropane, dien=diethylenetriamine). All of these compounds are built by B5O10 clusters and Al O4 groups which are alternately connected to give a 3-D architecture. Compounds 3–1 and 3–3 have NLO properties for their acentric structure.Compound 3–1 features the 3D open framework interpenetrated by metal-organiccoordination chains which is quite rare. The compound displays extensive luminescence and exhibits SHG efficiency approximately 3 times that of KH2PO4(KDP). In compound 3–2, cadmium complexes form double metal complexes by en molecules, and are connected with the oxoboron clusters by the metal-oxygen bonds.In compounds 3–2 and 3–4, zinc complexes are filled in the channels and stabilize the framework not only through hydrogen bonds but also the metal oxygen bonds.The fourth chapter reports four new alkali-alkaline earth metal borates which are synthesized under hydrothermal or solvothermal conditions: Li2[Mg B12O14(OH)12]·-2H2O(4–1), Li4Ca2[B8O12(OH)4]2·3H2O(4–2), [Sr B5O8(OH)]·H2O(4–3) and[Ba B5O8(OH)]·H2O(4–4). In compound 4–1, the sandwiched structural building unit(SBU) [Mg B12O14(OH)12]2- connects six others to form a 2-D layer vis Li O4 polyhedron in bc plane and further form the 3D supramolecular networks through O-H…O hydrogen bonds. The SBU [B8O12(OH)4]4- for compound 4–2, are connected by O vertices to form a 2-D layer with 13-memered ring(MR) channels along the a-axis. The double layers are linked by Ca O8 polyhedron and further form a 3D framework by Li O4 polyhedron. Compounds 4–3 and 4–4 are isostructural with different alkaline earth metal. The SBU of [B8O12(OH)4]4-clustersare connected through O vertices to form layers with 9- membered ring in ab plane.The five chapter reports five new inorganic-organic hybrid borates and other metal borates which are synthesized under hydrothermal or solvothermal conditions:Na[Pb4(H2O)](B5O9)2BO3(5–1), [Li(H2O)4]2[Cu(H2O)6][Cu(H2O)5]2[B4O5(OH)4]-4H2O(5–2), [Cu(en)2(H2O)2][Cu(en)2(B(OH)3)2][B4O5(OH)4]2·H2O(5–3), [KB6O9-OH]en·H2O(5–4) and [B5O6(OH)4]MPD(5–5)(MPD=2-methyl-3,4,5,6-tetrahydropyrimidin-1-ium). In compound 5–1, the structural building unit, B5O12 cluster, connects adjacent six same ones to form a 3-D oxoboron framework with 8-and 10-MR channels along the a-axis. The Pb atoms and coordinated water molecules are located in the 8-MR channels, while the 10-MR channels were occupied by the chains built by Na atoms and the BO3 groups. Second-harmonic generation(SHG)measurements on the powder samples reveal that 5-1 exhibits SHG efficiencyapproximately 2 times that of KDP. Also it has a UV cutoff edge below 220 nm. In compound 5–2, the SBU [B4O5(OH)4]2-, connects others to form a 3-D supramolecular network through O-H…O hydrogen bonds and the Cu2+- and Li+-centered polyhedra are filled in the channels. And in compound 5-3,[B4O5(OH)4]2- clusters form a 2-D layer through O-H…O hydrogen bonds along the b-axis, which are linked by [Cu(en)2(B(OH)3)2]2+ cations forming a 3D framework. In compound 5-4, the SBU B6O11(OH) clusters are formed a layer through O atoms with9-membered channels, and then form 3-D networkthrough K-O bonds,, and en moleculars are linked to the oxoboron framework by the B-N bonds. Compound 5-5 is kind of a borate templated by organic amine molecules which the SBU [B5O6(OH)4]-clusters are connected through O-H... O hydrogen bonds to form 3D supramolecular.On the basis of the previous study of borates, we still adopt the hydrothermal or solvothermal conditions through changing the center metal, organic ligands, reaction time and temperatures to make novel structures of borates, and investigate the NLO properties of the acentric structures.