Solid-State Synthesis And Crystal Chemistry Of Chalcogenoborates Containing B₁₂Q₁₂(Q=S;Se) Clusters

With the development of high technology and the rapidly increasing demand of human beings for a higher quality of life,exploration of new materials with special structures,properties and functions becomes more and more important.Among numerous researches,designing compounds with completely novel structures is an extremely attractive and challenging topic.With the development of inorganic synthetic chemistry,a large number of binary and ternary compounds and structures have been discovered and studied,and many multinary inorganic compounds with rich structures have also been synthesized.However,the exploration of materials with novel structures and excellent physical and chemical properties has been never stopped,and hoped to enrich fundamental research or further develop new theories on this basis.From the perspective of scientific development,synthetic chemistry is the core of chemical science and the most powerful means for chemists to transform the world and create the future;From the perspective of acquiring new materials,crystal,with a periodic structure constructed by ordered functional motifs,can be designed and synthesized with new species by adjusting the types and combinations of motifs,so as to break through the limitations of element types and obtain materials with diverse functions,thus promoting the rapid development of materials science.Based on the above ideas,this thesis studies the rarely discovered chalcogenoborates,that is,the lattice position of O in borate structures is substituted by chalcogen element.Chalcogenoborates are a class of compounds with very distinctive structures,among which very rare ones contain B12Q12(Q=S,Se)cluster showing very special structures.Therefore,the purpose of this study is to synthesize novel chalcogenoborates crystals containing B12Q12 cluster and study their structures and optical properties.The main work of this thesis is as follows:1.Different elements and fluxes were introduced to regulate the structures and nonlinear optical(NLO)properties of polychalcogenoborates containing B12Q12 clusters.Six new pentanary chalcogenoborates have been synthesized by hightemperature solid-state reactions,namely,(Rb3I)[InB12(InS4)3],(K3Cl)[InB12(InSe4)3],(K3Br)[InB12(InSe4)3],(Rb3I)[InB12(InSe4)3],(Cs3Cl)[InB12(InSe4)3]and(Cs3I)[InB12(InSe4)3].They crystalize in the noncentrosymmetric hexagonal space group P6322,belonging to one kind of Kleinman-forbidden point group 622.Taking(K3Cl)[InB12(InSe4)3]as an example,its structure can be viewed as each B12 icosahedron connects with six InSe4 tetrahedra via edge sharing and two InSe6 octahedra via face sharing to form {[InB12(InS4)3]2-}? polyanion,which connect with each other to build a 3D honeycomb-like open-framework.The InSe6 octahedron shares faces with two neighboring B12Q12 clusters to form an[(InB12S12)11-]? chain along the c-axis,and imaginary[(K3C1)2+]? arranges along the c-axis.Optical properties tests show that the band gap of(K3Cl)[InB12(InSe4)3]is 2.02 eV and a weak SHG response.In addition,their electronic structures and optical properties were systematically studied with the density functional theory.2.The first chalcogenoborate including InS4,InS5 and InS6 polyhedra.KNa0.78Eu0.27In3.80B12S12(KNEIBS)was synthesized by a high-temperature solid-state reaction.There is complex disorder in the structure,which is the first study on the disorder structure of thioborates.As far as we know,there are two-types of connection around B12 icosahedra known,and each one contains only a single cluster.Different from these two styles,the structure of KNEIBS contains two B12 clusters that differ from the previous ones.Namely,each type-? B12 icosahedron is surrounded by two InS4 tetrahedra and four InSs trigonal bipyramids,whereas each type-? B12 icosahedron is surrounded by four InS6 octahedra,two InS4 tetrahedra and four InS5 trigonal bipyramids.Besides,diverse InSx(x=4,5,6)units co-exist in the structure,which is the second case for In-based chalcogenides.The structural complexity and novelty are well elaborated.Its optical properties and electronic structure were experimentally and theoretically studied,and the structural features are compared with other chalcogenoborates containing B12Q12 clusters.3.The first thioborate with mixed valence rare earth ion.On the basis of the previous chapter,KEu2In3B12S13(KEIBS)was obtained by adjusting the proportion of raw materials.The three-dimensional structure features six InS6 octahedra consolidated B12 icosahedron built {[In3B12S12]5-}? polyanionic framework and unique[In6S6]6+12membered ring,representing a new type of compound.The {[In3B12S12]5-}? cluster is also different from the other known thioborates.The structural chemistry,optical properties,magnetism and theoretical calculation of KEIBS are systematically studied.This work not only provided a new type of thioborate,but also injected new vitality into boron cluster chemistry.