Synthesis And Properties Of Viologen Ligand:Dibromide-1,1'-bis(4-carboxyphenylene Methylene)-4,4'-bipyridine And Its Coordination Polymers

Chromic materials,especially photochromic materials,have been used in all aspects of social development in today's society.Viologen photochromic compounds have attracted more and more attention due to their excellent properties.Due to its unique electron-deficient system of viologen,Viologen provides a good path for photoinduced electron transfer.In this paper,we first constructed a viologen ligand with bicarboxyl group:dibromide-1,1'-bis?4-carboxyphenylene methylene?-4,4'-bipyridine?L?.Due to the lack of electron,viologen is a good electron acceptor,which is conducive to electron transfer.We characterize and analyze the ligand,and study its photochromic and photocontrolled fluorescence properties.Then,the ligand L was assembled with metal ions and the second ligand to form metal-organic coordination compound.The viologen ligand L,metal cadmium and the second ligand?benzimidazole?BM,compound 1?,pentaphenyltetrazole?PZ,compound 2??were self-assembled to form two viologen-metal coordination compound?compound1=[Cd?BM??H₂BpybcBr₂?Br]·H₂O,compound 2=[Cd?PZ??H₂BpybcBr₂?NO₃]·2H₂O?.The two compounds were characterized by IR and TG,and their X-ray diffraction data were collected to obtain the single crystal structure.The metal centers of compound 1 are linked by carboxyl oxygen atoms of viologen ligand to form one-dimensional chain structure,while the metal cadmium of compound 2 coordinates with the oxygen atoms of viologen ligand carboxyl,and the metal centers are connected by ligands to form one-dimensional dentate structure.In this paper,the photochromism,photocontrolled fluorescence and organic amine induction properties of compound 1 and compound 2 were investigated.Under 300 W xenon lamp irradiation,the color of compound 1 changed from light yellow to light green,and compound 2 changed from yellow to blue.There was a reversible photochromism process in compound 2.The fluorescence intensity of compound 1 and compound 2 changed significantly under light irradiation.The study on the relationship of their structure and properties shows that compound 1 and 2 can be used as good photochromic-fluorescent molecular switch materials.At the same time,the sensing properties of compound 2 showed that it could instantaneously response to aniline,one of the three main carcinogen,which indicated that compound 2 could be used as an organic amine probe.