Construction And Photochromic Property Of 2,4,6-Tri(2-Pyridyl)-1,3,5-Triazine Electron Donor-Acceptor Hybrid Systems

Electron donor-acceotor hybird photochromic systems have received extensively attention,due to their important potential and practical applications in displays,optical switching,information storage,memory and other high-tech fields.Although a large of achievements have been obtained in the fabrication of photochromic systems,the effective modulation of photoinduced intermolecular electron transfer（ET）is still a challenge.In order to solve this problem,researchers mainly focus on two appropriate matching strategies including electron donating-accepting capabilities and interfacial contacts of electron donors/acceptors.A large number of research show that the electron donating-accepting matching rules are"strong strong matching"and"weak weak matching".However,the performance optimization of photochromic system through reasonably modulating the interfacial relationship of electron donors/acceptors is still in its infancy stage.2,4,6-tris（2-pyridyl）-1,3,5-triazine（2-TPT）is a type of excellent strong electron deficient acceptor with largeπ-conjugated system composed of one triazine ring and three pyridine rings,which can easily interact with electron-rich components by means of diverse weak interactions.Meanwhile,2-TPT is a rigid multidentate chelating ligand and can coordinate with metals to form excellent functional coordination polymers.Aromatic carboxylic acids are widely used to construct diverse structural coordination polymers because of their unique electron-rich properties and multiple coordination modes.Therefore,the hybridization of2-TPT and aromatic carboxylic acids through the coordination interaction of metal ions can not only effectively adjust the interfacial relationship of electron donors/acceptors,which is an effective strategy for the construction of electron donor-acceptor photochromic hybrid systems.Based on the above consideration,in this dissertation,nine electron donor-accepter hybrids,[Zn（2-TPT）（p-BDC）]·DMF（1）,[Zn（2-TPT）（1,4-NDC）]·2DMF（2）,[Zn（2-TPT）（2,6-NDC）]·DMF（3）[Zn（2-TPT）（BPC）]·2DMF（4）,[Zn（2-TPT）（o-BDC）]（5）,[Cd（2-TPT）（o-BDC）]（6）,[Zn（2-TPT）（2,5-FCA）]（7）,[Cd（2-TPT）（2,5-FCA）]·1.5H₂O（8）and[Mn（2-TPT）（2,5-FCA）]（9）,（p-H₂BDC=phthalic acid,1,4-H₂NDC=1,4-naphthalenedicarboxylic acid,2,6-H₂NDC=2,6-naphthalenedicarboxylic acid,H₂BPC=biphenyl-4,4’-dicarboxylic acid,o-H₂BDC=phthalic acid,2,5-H₂FCA=Furan-2,5-dicarboxylic acid）have been constructed by assembly of 2-TPT with strong electron-deficient ability and flexible coordination modes,different types of auxiliary ligands and metal ions through the solvent evaporation method/solvothermal synthesis technique.In this dissertation,by modulating different types of carboxylic acid ligands and metal ions,the interfacial relationship of electron donors/acceptors has been effectively regulated,the subtle balance between intermolecular CT and ET has been verified and the photochromic properties have been optimized.The relationship of compositions,structures and photochromic properties of 2-TPT-based electron donor-acceptor systems has been established.The main research conclusions are as follows:（1）Four one-dimensional（1D）2-TPT-based coordination polymers 1-4 have been constructed by bridging carboxylic acid electron donors with different charge density and space size and 2-TPT electron acceptor through metal ions.Although four compounds exhibit excellent photochromic behaviors,their coloration contrast are significantly different before and after illumination,which are mainly attributed to the electron-donating ability of different carboxylic acid electron donors and the obviously distinct interfacial relationship of electron donors/acceptors.This part of the work,the effectively regulating effect of different auxiliary ligands on photoinduced intermolecular ET and photochromic properties has been ascertained,and the delicate balance of intermolecular CT and ET has been preliminarily realized.（2）Five 2-TPT-based electron donor-acceptor hybrids 5-9 with different stacking modes have been constructed by assembly of the 2-TPT electron acceptor with o-H₂BDC and2,5-H₂FCA through different types of metal ions,respectively.5 and 6 are binuclear cluster and 1D chain,which generate distinct 2D supramolecular networks through weak interactions,respectively.7 is 1D chain-like structure,which are connected with each other through weak interactions to give rise to a 3D supramolecular network.Both 8 and 9 are 1D double chain-like structure.2D supramolecular network is formed through weak interactions in 8,while the weak interaction is not obsvered in 9.5-9 show obviously distinguishing photochromic behaviors,which are mainly reflect in photoresponsive rate and coloration contrast.The photochromic performance of 5 and 7 are obviously better than that of 6 and 8,respectively,while 9 is non-photochromic.These obviously discriminative photochromic behaviors are largely attributed to the different packing modes of crystal structures and the discriminative relative position of electron donors/acceptors caused by different types and coordination patterns of the metal centers.This part of the work,the modulating effect of metal ions on photoinduced intermolecular ET and photochromic properties has been fully illustrated.