Synthesis,Structure And Characterization Of Borates With Open-framework Under Hydro/Solvothermal Conditions

Borates as an important branch of inorganic materials,which have been widely focused in recent years due to their rich structures and wide potential applications in mineral,fluorescence,second order nonlinear optical,catalytic and biological.It has been proved that boron atoms reveal two kinds of coordination models with BO₃ and BO₄ which can linked together through common vertices or edge in varying ratios to build different B-O clusters and then further polymerize into infinite chains,sheets and frameworks.Synthesis of novel structure and excellent performance borates have been a hot topic.Based on the previous work of our group,the author designed and synthesized some open-framework compounds of main group metal borates,alkali-metal and alkaline-earth-metal borates,organic amine and metal complexes borates under hydro/solvothermal conditions.These structures were determined by single crystal X-ray diffraction and further characterized by X-ray power diffraction,ultraviolet spectrum,FT-IR and thermogravimetric analysis.We also examine SHG properties and fluorescences of some compounds.We get three types of compounds:1.Three Aluminoborates with 3D open-frameworks.[(C₄H₁₀N)₄][Zn@B₁₂O₂₀][Al B₅O₁₀]（3-1）[(C₄H₁₀N)₄][Co@B₁₂O₂₀][Al B₅O₁₀]（3-2）[Cd（en）₃][Al B₇O₁₂（OH）₂]（3-3）Of all these structures,Compound 3-1 and 3-2 are isostructural.They are based on two different oxoboron clusters([B₅O₁₀]clusters and[M@B₁₂O₂₄]（M=Zn,Co）clusters)to build[M@B₁₇O₃₀]?1D chain structure,which are further interconnected by Al O₄ tetrahedra into a 3D open framework.Both left-handed and right-handed helices 10MR exist along the c-axis.Interestingly,the pyrrolidine was originated in situ from the precursor1,4-diaminobutane.The second order nonlinear optical effects are 1.9 times and 0.4 times that of KDP,respectively.And the compound 3-1 also has fluorescence property.In aluminoborate 3-3,Al O₄ tetrahedra,chain-like[B₄O₆（OH）₂]clusters and crab-like[B₆O₁₂]clusters interconnect to form another new B-O-Al 3D frameworks with 8-and 16-ring helical channels,15-ring channels.The[Cd（en）₃]²⁺cations locate in the channels of 3D framework,which serve as the structure direction agents.2.Two componds of alkali-alkaline earth metal borates.Na₂B₁₀O₁₄（OH）₄·H₂O（3-4）[Ca₂B₅O₉]·[H（OH）₂]（3-5）Compound 3-4 exists two stereo-isomeric configurations of the[B₅O₈（OH）₂]clusters,which are connected to each other by sharing O atoms to form a unique[B₁₀O₁₄（OH）₄]^2-clusters.And the adjacent[B₁₀O₁₄（OH）₄]^2-clusters form 1D oxoboron chains through sharing O atoms.The H-bonding and Na atoms between adjacent chains lead to 2D layers with-ABAB-sequence,which further linked by H-bonding to form 3D supramolecular network structure.3-5 is one of alkaline earth metal borates crystallizes in the asymmetric space group.The fundamental building blocks of compound 3-5 are B₅O₁₂ clusters which extend to a 3D framework with 9-ring channels along b-axis.The calcium atoms and two[H（OH）₂]^-groups are existed in the 9-ring channels to balance the charge.The second order nonlinear optical effect of 3-5 is about 3.5 times that of KDP.3.Three compounds of organic amines or metal complexes supported borates.[Zn（1,4-dab）][B₅O₈（OH）]（3-6）[C₇H₁₀N][B₅O₆（OH）₄]（3-7）[Co（1,2-dap）(C₆H₁₇N₃)][B₅O₆（OH）₄]₂·H₂O（3-8）Compound 3-6 is a hybrid borate with a 3D structure constructed from inorganic framework and organic components linked by Zn-N-C chains.The inorganic framework is a netural 2D layered structure which is built up by metal-centered wheel cluster[Zn@B₂₀O₃₆（OH）₄]and the organic part is 1,4-dab molecules.3-7 and 3-8 are two kinds of isolated borates which take the metal complexes and organic amine molecules as templates.The[B₅O₆（OH）₄]^2-clusters are connected through O-H…O hydrogen bonds to form 3D supramolecular structure.It is interesting to note that organic amines of these two structures happened in situ reaction.