Synthesis,Structure And Optical Property Of Unsymmetric Viologen-based Photochromic Hybrid Materials

Viologen-based photochromic hybrid materials have attracted more and more attention due to their excellent property.The main reason is that viologen is a good electron acceptor and will occur the electron transfer upon the light irradiation,thus the addition of viologen can enable its hybrid material to display excellent photochromic performance.In this thesis,transition metal and lanthanide metal ions were selected as inorganic components,and asymmetric viologen ligands were used as organic components.Based on the size effect,charge balance principle and other factors these two components can assemble into the same materials,whose photochromic characteristics are deeply studied by us.The synthesis,structure and optical properties of eight complexes are described and analyzed in detail,especially the mechanism of photochromism.This paper is divided into the following five parts:In the first chapter,there is a brief introduction on the research background,progress and practical application of viologen-based photochromic materials.The discoloration prin-ciple of photochromic complex is described in detail,and the application prospect of phot-ochromic complex is prospected.The second chapter,two supramolecular isomers: [Cd（CPBPY）（BDC）（H₂O）]n（1）and {[Cd（CPBPY）（BDC）].H₂O}n（2）（CPBPY = N-（3-carboxyphenyl）-4,4′-Bipyridiniu-m,BDC = terephthalate）have been achieved by hydrothermal synthesis from（HCPBPY）.Cl and p-phenylene dicarboxylic acid（H₂BDC）ligand with a transition metal Cd salt.Isomer 1 features（4,4）-topological layer constructed by edge-shared Cd2 SBUs and BDC2-linkers attached by N-pendent CPBPY groups.Isomer 2 has（6,3）-topological layers with Cd atoms as nodes and BDC2-and double CPBPY as linkers,which are four-fold interpenetrated into 3D network.Isomer 1 possesses reversible photochromic behavior with quick-switchable luminescence in the solid state,the photoproduct 1a is stable for months even irradiated by sunlight under oxygen atmosphere.The very long lifetime of stable charge separation state in 1a indicates possible application in the conversion of solar energy to electrical energy.However,compound 2 does not show photochromic behavior even after exposure to UV light for more than two hours.The third chapter,a series of four photochromic fluorescent metal organic skeletal complexes: [Cd（CPBPY）（BDC）（H₂O）₂]（3）,[Cd（CPBPY）（o-BDC）（H₂O）₂]（4）,[Cd₃（C PBPY）₂（BDC）3]（5）and [La2（NO₃）6（H₂O）4（CPBPY）₂.（H₂O）₂]（6）have been achieved by hydrothermal synthesis from（HCPBPY）.Cl ligand with different transition metal salts and lanthanide metal salts.Compounds 3,4 and 6 display reversible photochromic behavior with quick-switchable luminescence in the air,however,compound 5 only exhibit photochromic behavior in an inert gas atmosphere.It is worth noting that the coloring compounds 4a and 5a can be quickly decolored in the air atmosphere,so these materials can be used as the oxygen sensors.The fourth chapter,two fluorescent metal organic skeletal complexes: [Cd（CPY）₂]（7）and Zn CPy]（8）have been achieved by hydrothermal synthesis from（HCPBPY）.Cl and p-phenylene dicarboxylic acid（H₂BDC）ligand with transition metal Zn and Cd salt.Compounds 7 and 8 do not show photochromic behavior,mainly because in situ hydrogenation reaction have occurred on the pyridine ring of CPBPY ligand.The last chapter,this paper summarizes the work of this paper and looks forward to the prospect of this research.