Copper(Ⅰ) Halide-based Hybrid Materials: Synthesis, Structure And Properties

Copper（Ⅰ） halide-based compounds have attracted great attention due to theirintriguing structures, rich photophysical behaviors and high luminance efficiency. Todate, a large number of such compounds with different structure and dimensions havebeen reported. Usually, the compounds are self-assembled by inorganic componentsand organic components. The inorganic component provides good mechanicalstability, thermal stability and electronic characteristics. The organic componentprovides structural adjustability, mechanical plasticity and excellent opticalperformance. Based on the reported literature, the emissions at room temperature aremainly attributed to LMCT （ligand to metal charge transfer） and a combination of atriplet “cluster-centered”（³CC^*） exited state consisting of³XMCT^*（halide to metalcharge transfer） and a CuId10�'d9s1transition. Although many experimental andtheoretical studies of the synthesis and luminescence properties of copper（Ⅰ）halide-based compounds have been reported, there are only a few systematicinvestigations about the relationship between the modifications of the crystal structureor of the environment and changes in the emissive behavior. Therefore, it is anenormous challenge for researchers to rationally design, precisely control, andeffectively reassemble new copper（Ⅰ） halide-based compounds with variousluminescence properties. The following describes the layout of this thesis that sets outto investigate this important topic.In the first chapter of five, the concepts, research methods, history and newdevelopments of copper（Ⅰ） halide-based compounds are introduced. At the end of thischapter, the importance of the project is described. In the second chapter, we show four copper（Ⅰ） halide-based compounds(C₁₀H₂₂N₂)₂[Cu₄I₈]（1）,(C₁₀H₂₂N₂)₂[Cu₄I₄Br₄]（2）, C₂₀H₄₄N₄[Cu₄I4Br₄]（3） andCu6I8(C₈H₁₈N₂)·CH₃OH （4） through solvothermal in situ reaction. Compounds1and2have similar structures, the only structural difference being that μ1-X sites of thelatter are occupied by Br-anions rather than Ⅰ-anions. Compounds2and3havesimilar anion copper（Ⅰ） halide clusters, the difference being that they have differentorganic species. Although many experimental and theoretical studies of the synthesisand luminescence properties of cubane-like clusters Cu4Ⅰ4have been reported, thereare only a few systematic investigations about the relationship between themodifications of the crystal structure or of the environment and changes in theemissive behavior. The3D framework of compound4was constructed by Cu⁺and I^-.This is the first report of such3D copper（Ⅰ） halides cluster. Interestingly, compound4exhibits strong blue luminescence at ambient temperature, so we have tested anddiscussed its luminescence properties. By comparing the structures and the synthesisconditions of these four compounds, it can be seen that the organic cations play animportant role in the assembly of anion copper（Ⅰ） halide clusters. The role of theorganic species can be classified into three categories: templating, charge balancing,and space filling. First, because the nitrogen atoms of them are alkylated, the organiccations will serve as templates in the formation of anion copper（Ⅰ） halide clusters.Secondly, the organic species have positive charge, which could balance the negativecharge of the anionic clusters. Thirdly, the organic species are located among theanionic clusters, which exhibit the space filling effect via weak C–H···halogenhydrogen bonds.The third chapter describes two copper（Ⅰ） halide-based compoundsCu₄I₃（DABCO）₂]I·I₂（5） and [Cu₆I₆Br₂C₁₆H₃₂N₄]（6） with3D framework generatedfrom solvothermal reaction. Compound5has a cationic framework and the channelsare occupied by I₂and I^-. The guest I₂molecules can move freely in and out of thehost-framework and the guest I^-can be exchanged by SCN^-, so the compound exhibitsiodine release/adsorption and ion-exchange properties. In terms of the luminescentproperties, compound5exhibits obvious blue shift after ion-exchange with SCN^-, and thus can be used for sensing SCN-. Compound6has shown a2-fold interpenetrated3D framework. Each independent3D framework is “pillared-layered” and constructedby copper halide layer [Cu₆I₆Br₂]^2-and the cationic ligand. Compound6exhibits“thermochromic luminescence” properties. The luminescent property of compound4shows obvious red shift with decreasing temperature from300K to6K.In the fourth chapter, three copper（Ⅰ） halide-based compounds Cu₂I₂（C₇H₉N）₂（7）,Cu₄I₄(C₁₀H₈N₂)₂（8） and Cu₃I₂C₂H₂N₃（9） were prepared by Cu（Ⅰ） salt and simpleorganic ligand2,6-dimethyl pyridine ligand,2-cyano-methyl-phenyl acetonitrile and1,2,4-triazole. The structure of the compounds was formed by different copper（Ⅰ）halide cluster and organic ligand. Compound7is constructed by Cu₂I₂dimer and2,6-dimethyl pyridine. Compound8has a two-dimensional layer which was composedby cubane Cu₄I₄cluster and2-cyano-methyl-phenyl acetonitrile. The3D frameworkstructure of compound9is formed by copper（Ⅰ） chains and1,2,4-triazole.Comparison of the structures and the synthesis conditions of these three compoundssuggests that organic ligands play an important role in the formation process ofcopper（Ⅰ） halide cluster. At room temperature, these three compounds show obviousphotoluminescence, so we have tested and discussed their luminescence properties.The last chapter provides the summary and conclusion of the research project.