Design,Synthesis And Photochromic Performance Research Of Naphthalenediimide-Based Coordination Polymers

Photochromic materials composed of electron donor-acceptor units possess excellent naked-eye detectable performance,which display significantly applications in the fields of sensors,protections,information storages,displays and optical switching.To realize the two matching rules of electron donating-accepting abilities and interfacial relationship（the position relationship）between the electron donors（EDs）and electron acceptors（EAs）are key factors for the construction of electrontransfer（ET）photochromic materials with excellent properties.Although some important breakthroughs have been obtained through modulating the matching rule of electron donating-accepting abilities of electron donors/acceptors（EDs/EAs）,few studies have been done to regulate the interfacial relationship of EDs/EAs and the intrinsic relationship between interfacial relationship and photochromic properties is still unclear.Therefore,the assembly of EDs and EAs in a specific way to realize the reasonable matching of the interfacial relationship has been the key scientific issues to be addressed for optimizing the properties of photochromic materials.Naphthalenediimide（NDIs）possess a large positive quadrupole moment,good modifiable property and high redox activity,which are an ideal type of component for the construction of excellent photochromic materials.Anchoring aminomethylpyridine at both sides of the imide ring edows themselves flexibility,which will enrich the interfacial relationship of EDs/EAs.Therefore,the coordination polymers（CPs）with different structures could be constructed by the combination of NDIs and electron-rich donors through metal coordinationand the flexible and diverse weak interactions between EDs and EAs will be modulated,which is an effective strategy to optimize the properties of crystalline hybrid photochromic materials.Based on above consideration,eight different CPs,[Cd（3-DPMNI）（1,4-HNDC）₂（DMF）]（1）,[Cd（4-DPMNI）（1,4-NDC）]·DMF（2）,[Zn（3-DPMNI）_0.5（2,6-NDC）]·3DMF（3）,[Cd（3-DPMNI）（2,6-NDC）_0.5（NO₃）]（4）,[Co（3-DPMNI）（2,6-NDC）_0.5（NO₃）]（5）,[Cd₂（3-DPMNI）_1.5（4,4’-BPC）₂（H₂O）₃]·DMF（6）,[Cd（3-DPMNI）（2,2’-BPC）]（7）and[Cd（3-DPMNI）（4,4’-SBC）]（8）,（1,4-H₂NDC=1,4-naphthalenedicarboxylic acid,2,6-H₂NDC=2,6-naphthalenedicarboxylic acid,4,4’-H₂BPC=4,4’-biphenyldicarboxylic acid,2,2’-H₂BPC=2,2’-biphenyldicarboxylic acid,4,4’-H₂SBC=4,4’-stilbenedicarboxylic acid,DMF=N,N’-dimethylformamide）have been synthesized through solvothermal conditions by the assembly of positional isomeric N,N′-bis（3-/4-pyridylmethyl）-1,4,5,8-naphthalene diimide（3-/4-DPMNI）ligands as EAs,electron-rich aromatic carboxylic acids as EDs and metal ions with different coordination mode as nodes.The effects of positional isomerism of substituents at both sides of NDIs,potential EDs and metal types on the interfacial contacts of the EDs/EAs systems have been systematically analyzed.The effective modulation of photoinduced intermolecular electron transfer（PIET）and photochromic properties has been achieved.The relationship of the composition,structure and photochromic properties of3-/4-DPMNI-based EDs/EAs systems has been established.The main contents of this thesis are as follows:（1）Two novel naphthalenediimide-based（NDIs-based）CPs have been designed and synthesized by the assembly of a pair of positional isomeric electron-deficient 3-/4-DPMNI and electron-rich 1,4-H₂NDC,respectively,in the presence of cadmium ions.The usage of positional isomeric 3-/4-DPMNI ligands leads to the generation of one-dimensional（1D）chain and 2-fold interpenetrated three-dimensional（3D）framework for 1 and 2,respectively.Interestingly,both compounds exhibit outstanding ultrafast visible-light photochromic properties based on the PIET.1 changes from yellow to dark brown within 5 s and 2 turns from kelly to dark green for 10 s.The excellent photochromic properties of 1 and 2 should be ascribed to the formation of the typical arrangements of EDs/EAs in the interfacial contracts（ED-EA-ED for 1 vs.ED-EA-EA-ED for 2）.Notably,both 1 and 2 are highly photosensitive to the blue light wavelengths,which can be viewed as a representative type of photochromic materials for detection and filtration of blue light.（2）Three CPs of 3-5 have been constructed by the assembly of 3-DPMNI and2,6-naphthalene dicarboxylic acid with different coordination modes of metals,respectively.3shows 3D pillar-layer architecture built of carboxylate layers and naphthalenediimide pillars,in which DMF are filled in the channels as guest molecules.The compound exhibits outstanding photochromic performance due to PIET between the electron-rich guest molecules and electron-deficient host framework（host-guest ET）.Of note,the host framework of 3 cannot show a macroscopic color change owing to the absence of the ET pathway.Nevertheless,it exhibits discriminative photochromic behavior in the presence of electron-rich solvents,which is mainly attributed to different electron-donating abilities of guest solvents and distinct interfacial contacts of EDs/EAs.Furthermore,it can also show discriminative ET chemochromic response to different sizes and shapes of organic amines,which can be potentially used for the visual detection of electron-rich organic amines,especially n-butylamine（n-BUA）.4 and 5 are isostructural two-dimensional（2D）layered structures.4 shows excellent photochromic properties,while 5 exhibits no photochromic behavior,which are mainly attributed to the d-d transition of different metal ions and their distinct electronegativity and coordination mode.These phenomenons show the effective regulation of the electronegativity and coordination mode of metal ions on the structure and interfacial relationship of EDs/EAs,which further realize the modulation of PIET and photochromic properties.（3）Three CPs 6-8 have been prepared by the assembly of 3-DPMNI and aromatic carboxylic acids with different size,shapes and charge density respectively,in the presence of cadmium ions.6 shows a 2-fold interpenetrated 3D framework,7 is a 2D layered structure and 8 displays a 3-fold interpenetrated 3D network.They show distinct photochromic behaviors,in which 6 shows rapid obvious photochromic property,7 reveals unconspicuous photochromic behavior,and 8 exhibits no photochromic behavior.These phenomenons are mainly contributed to the influence of size matching degree of EDs/EAs and the conjugation degree of EDs on the interface relationship and the photochromic properties.