Synthesis, Characterization And Crystal Structure Of Novel Transition Metal Borates

Boron can form a large variety of compounds because of the complexityof the structures involved. So the study of the synthesis and crystal structure of borateshas attracted much attention in recent years. Transition metal borates have attractedmuch attention due to their interesting structural features and various potentialapplications in several areas such as catalysis, electrical conductivity, magneticmaterials, non-linear optics properties and microporous materials. Because thecooperative effect of BO₄ and PO₄ groups may give materials much better properties, theresearch on borophosphates has caused great interest and become a hot field.In this thesis, three novel transition metal borates and three new non-targetcrystals have been synthesized by the reaction between boric acid/alkali-metal borateand transition-metal salts under mild solvothermal conditions. Their crystal structureshave been determined by single-crystal X-ray diffraction data and further characterizedby element analysis, FT-IR spectrum, Raman spectrum, XRD and simultaneousDTA-TG..(1) A novel inorganic-organic hybrid transition metal borate[Ni(en)₃]₂(H₃BO₃)(MoO₄)₂·(6H₂O) has been synthesized by hydrothermal reaction. Themolecular structure of the compound consists of two MoO₄^2- tetrahedra, two [Ni(en)₃]²⁺octahedra, a H₃BO₃ unit and six H₂O molecules, in which these clusters are absoluteand self-assemble via N-H…O and O-H…O hydrogen bonds to form a wide range ofsupramolecular frameworks. It is worth noting that [Ni(en)₃]₂(H₃BO₃)(MoO₄)₂·(6H₂O)is the first example of organic-inorganic hybrid molybdenum borate containing H₃BO₃molecule.(2) Two transition metal borophosphates, NaCo(H₂O)₂[BP₂O₈]·H₂O andNaNi(H₂O)₂[BP₂O₈]·H₂O, have been prepared by solvothermal meyhod. Single crystalX-ray diffraction analysis shows that the molecular structures ofNaCo(H₂O)₂[BP₂O₈]·H₂O and NaNi(H₂O)₂[BP₂O₈]·H₂O are same. The condensation ofPO₄ and BO₄ tetrahedra through sharing vertices forms tetrahedral ribbons¹âˆž{[BP₂O₈]^3-}. The tetrahedral-tetrahedral helical ribbons linked by the MO₆ octahedra form chiral open-framework.(3) Three novel non-target crystals, K₂[B₆O₉(OH)₂], K₂Ba[B₄O₅(OH)₄]₂·9H₂O and[Co(C₄H₁₃N₃)₂]Cl₂·H₂O, have been synthesized by solvothermal synthesis and aqueoussolution reaction. The crystal structure of K₂[B₆O₉(OH)₂] consists of K-O polyhedra and1-D stepped polyborate chains constructed by new [B₆O₉(OH)₂]^2- fundamental buildingblocks with 3, 8-membered boron rings. The molecular structure ofK₂Ba[B₄O₅(OH)₄]₂·9H₂O is composed of two isolated tetraborate anions [B₄O₅(OH)₄]^2-,two nine-coordinated potassium cations and two nine-coordinated barium cations. Thecrystal structure of [Co(C₄H₁₃N₃)₂]Cl₂·H₂O consists of an isolated [Co(C₄H₁₃N₃)₂]²⁺cation, two chlorine anions and a water molecule. It is worth noting that K₂[B₆O₉(OH)₂]is the first example of hexaborate in alkali borates.