Synthesis,Structures And Properties Of Alkali Metal Borates Under Solvothermal Condition

Borates show abundant structure types,which are known as nonlinear optical materials(NLO)materials in the ultraviolet(UV)and deep UV region.In this paper,four inorganic-organic hybrid alkali metal borates were successfully synthesized by solvothermal method:Na₃[B₆O₁₀]·[HCONH](1)?Na₂[B₁₀O₁₆(OH)₂]·[H₂en]·H₂O(en=H₂NCH₂CH₂NH₂)(2)?Na₂[B₁₀O₁₆(OH)₂]·[H₂dap]·2H₂O(dap=H₂NCH₂CH₂CH₂NH₂)(3)?Na₆[B₁₀O₁₆(OH)₂]·[HNCONHCONH](4).And four cases of alkali borates were synthesized:Na₃[B₅O₈(OH)₂]·4H₂O(5)?Rb₂[B₆O₉(OH)₂](6)?NaK[B₅O₈(OH)]·H₂O(7)?NaRb[B₅O₈(OH)]·H₂O(8).Their structures were confirmed by X-ray single crystal diffraction,X-ray powder diffraction,infrared absorption spectra and thermogravimetric analysis.The UV-vis diffuse reflectance spectra of the above eight compounds were determined.Besides,compounds 1 and 4 are non-centrosymmetric compounds.We measured their nonlinear optical properties(SHG).Compound 1 crystallizes in the non-centrosymmetric orthorhombic space group P2₁2₁2₁.Each B₆O₁₀in the compound is connected with six adjacent B₆O₁₀units to form a three-dimensional grid structure.Sodium ions and formamide ions are filled in the skeleton.The SHG response of the powder is similar to that of KDP,and the absorption of UV-vis diffuse reflectance spectrum is located in the deep UV region.It is a good inorganic organic hybrid nonlinear crystal material.Compound 2 crystallizes in the monoclinic space group P21/m.The B5O9 cluster is the basic structural unit of the compound,which forms a nine membered ring layered structure with sodium ions,water molecules and ethylenediamine ions filling in the interlayer..The UV-vis diffuse reflectance spectra shows that its absorption edge is located in the deep UV region.Compound 3 crystallizes in the orthorhombic space group Pbca.The B₅O₉cluster is used as the basic unit to form a layered anion framework.Sodium ions and1,3-propanediamine ions are filled in the interlayer to balance the charge.The UV-vis diffuse reflectance spectra shows that the crystal has good transmittance in deep UV region.Compound 4 crystallizes in the non-centrosymmetric monoclinic space group Pc.The anion cluster of the compound is composed of two different B₅O₉units,and has a nine membered ring layered structure in space.Sodium ions and organic amine are filled between the layers.The SHG response of the compound is similar to that of KDP and phase matched.The UV-vis diffuse reflectance spectrum shows that the cut-off edge of the crystal is lower than 190 nm,which indicates that the crystal is a new deep UV nonlinear optical materials.Compound 5 crystallizes in the orthorhombic space group Pbcn.Its anion skeleton is a layered structure composed of B₅O₁₀clusters.Sodium ions and water molecules are filled between the layers.The absorption edge of the crystal is located in the UV region.Compound 6 crystallizes in the monoclinic space group P2₁/n.The B₆O₁₁cluster in the crystal structure is composed of two nearly vertical B₃O₇,which is 1D chain in the space frame,with cations filling on both sides of the chain.UV-vis diffuse reflectance spectrum analysis shows that the crystal has good transmittance in deep UV region.Compound 7 and Compound 8 crystallizes in the triclinic space group P1.They are isostructural compounds with 2D layered structure constructed by B₅O₉cluster,which is similar to the structure of SBBO(Sr₂Be₂B₂O₇).The UV-vis diffuse reflectance spectra showed that the absorption edge of compound 7 was in the deep UV region,and the absorption edge of compound 8 was in the UV region.