Syntheses And Photochromic Properties Of Viologen-Based Crystalline Materials

MOFs are a class of crystalline materials constructed by metal ions and organic ligands through coordination.Material scientists pay much attention to these materials because they can be used in store energy,separation,catalysis potentially.Chromic materials refer to the color change when they are stimulated by photo irradiation,heat,pressure,gas,solvent effect and so on,therefore,they can be used as sensors for these stimuli.Among them,color change caused by photo irradiation is called phtochromic material.In recent years,due to the rise of MOF materials,scientists turn their attentions to preparation of metal-organic hybrid photochromic MOF materials.Viologens?1,1?-disubstituted-4,4?-bipyridyl?possessing electron-deficient property,redox activity,are a class of suitable ligands to construct metal-organic hybrid photochromic materials.During the development of past ten years,a number of viologen-based crystalline phtochromic materials have been synthesized.Material scientists obtained their structures and photochromic phenomena,and developed multifunctional viologen-based metal-organic photochromic materials gradually.It means that this kind of materials will move towards more practical directions in the future.Therefore,syntheses and studies these materials have a great significance to the development of science and technology and human progress.However,syntheses of metal-viologen hybrid crystalline photochromic materials remain face with many challenges,such as it is difficult to predict the properties of final products,solid materials are limited by molecular configurations and so on.Research the effect of molecular configurations on photochromic properties will help people develop this kind of materials precisely.The research results of this paper are as follows:1.We selected a flexible bipyridinium salt derivative containing nitrogen atom on the end as the ligand,combining with m-H₂BDC,by solvothermal synthetic method,and gained two metal-controlled metal-viologen coordination polymers.Under the same condition,they exhibit obvious differences on photosensitiveness,stabilities of photoproducts.we studied their photochromic mechanisms and the effects of metal centers on their photochromic properties at the same time.this work can provide a valuable example for discussing the relationships between structures and properties of viologen-based crystalline photochromic materials.2.By solvothermal synthetic method,we gained a cd-viologen hybrid compound with strong photosensitivity.The mechanism of photochromism was explained and the property of photocontrolled fluorescence was studied and we also explored its application in ink-free erasable printing.The result showed that this compound was a solid intelligent molecular material which can regulate its fluorescence emission intensity,and it can be used in ink-free printing environment friendly materials.In conclusion,in this paper,by elaborate design at the molecular level,we introduced the viologen into metal-organic coordination polymer,and obtained metal-viologen hybrid crystalline photochromic materials.We studied their properties and mechanisms of photochromism,the relationships between configurations and properties,the property of photomodulated fluorescence,and the application in ink-free erasable printing.