Synthesis And Properties Of Photochromic Materials With Viologen Ligand Compounds

With the development of smart materials,stimulating response materials have attracted considerable attention.The stimulating response material refers to the material that can detect,judge and deal with the stimuli of the external environment.Some physical or chemical properties of the material will change.Stimulant response materials can convert unreadable external environmental factors（such as energy）into readable signals.Therefore,it is of great significance to research and develop stimulant response materials.Among them,photochromic materials are an important branch.Photochromic materials have been widely studied because of their rich color changes before and after irradiation.Electron transfer type photochromic materials have become a research hotspot.Many novel photochromic coordination compounds have been synthesized.However,there are relatively few coordination compounds with good stability,fast and multiple responses.In response to these challenges,three coordination compounds were synthesized by different metal ions（different coordination abilities）and different auxiliary ligands（different ability to give electrons）self-assembly using flexible viologen as functional ligand,and their properties and applications were studied in this paper.The main contents of this paper are as follows:1.By using the viologen ligand 1,1’-bis（4-carboxybenzyl）-4,4’-bipyridinium dichloride（H₂BpybcCl₂）as the functional ligand,5-methyl-1,3-benzenedicarboxylic acid（H₂L1）containing electron donor group as the auxiliary ligand,and manganese ion as the coordination center,a novel coordination compound[Mn₂（Bpybc）（L1）₂（H₂O）₂]·4H₂O（1）has been constructed by solvothermal method.Compound 1 is connected with L1 through Mn²⁺to form a layered structure,and the layers are connected through Bpybc to finally form a three-dimensional structure.Compound 1 exhibits photochromic behavior,and its light saturation state 1P has a long-term charge separation state.Compound 1 can be used as a potential inkless and erasable printing material.At the same time,1 has electrochromic properties.2.By using viologen ligand H₂BpybcCl₂ as the acceptor molecule,1,2,4,5-Benzenetetracarboxylic acid（H₄L2）containing carboxyl groups as the donor molecule,and zinc ion as the metal connection point,a novel coordination compound[Zn₂（Bpybc）_0.5（L2）（H₂O）]·DMA·H₂O（2）has been synthesized by solvothermal method.Zn²⁺and L2 are connected into a chain structure,and the chains are connected by bpybc to form a two-dimensional planar structure,and compound 2 forms a three-dimensional network stacking structure through hydrogen bonding.Compound 2 has rapid and reversible photochromic properties,and can show a color change visible to the naked eye after being irradiated by xenon lamp for 1 second.Compound 2 has potential applications in inkless and erasable printing and anti-counterfeiting.Compound 2 has photomodulated fluorescence properties.In addition,compound 2 also responds to ammonia and some primary amines.3.A novel compound[Cd₂（Bpybc）₃（L3）₂]Cl₂·10H₂O（3）has been synthesized by solvothermal method using H₂BpybcCl₂ as the functional ligand,3-chlorobenzoic acid（HL3）containing electron withdrawing groups as the auxiliary ligand and cadmium ion as the coordination center.Compound 3 is connected by Cd²⁺and Bpybc to form a one-dimensional chain structure with a frame,and L3 is suspended at both ends of the frame.Through double interpenetration andπ···πoffset stacking,compound 3 is finally a three-dimensional stacking structure.Compound 3 exhibits both photochromic and thermochromic properties.In addition,compound 3 also has a selective amine response,showing different color changes to ammonia,some primary and secondary amines.