| In recent years,metal–organic coordination polymers have been wildly applied in gas absorption/separation,catalysis,drug delivery and photochemistry.Viologens possess excellent properties like conductivity,redox-active nature and photochromism,which were taken in metal–organic coordination polymers as the mian functional building block to design and synthesis of multifunctional materials,exhibiting potential application in displays,optical switches,and optical data storage so on.Our project is to choose photochemical bipyridinium ligands as functional building block and introduce different types of auxiliary ligands.Through coordinate self-assembly,we have successfully obtained 6 bipyridinium-based coordination polymers,which are characterized by IR,EA,EPR,UV,TGA,X-ray single-crystal/powder diffraction studies.And we discuss the effect of different molecular configurations on the photochromic properties of the complexes and explore the thermochromism and solvatochromism abilities of some complexes.The innovative features of my work are described as follows:(1)We choose the flexible H2Bpybc Cl2 ligand to form novel compounds with different metal ions and auxiliary ligands under suitable experimental conditions,in which we can adjust the auxiliary ligands to control its structure and photoactivity.(2)Through changing the metal ions and choosing some similar multidentate carboxylic organic ligands like isophthalic acid(H2ip),2,6-Pyridinedicarboxylic acid(2,6-pydc)and 5-hydroxyisophthalic acid(H2hip),we obtained four compounds,such as{[Zn(Bpybc)0.5(ip)(H2O)]?0.5H2O}n(3-1),{[Cd(Bpybc)(2,6-pydc)]?2H2O}n(3-2),{[Zn2(Bpybc)2(hip)2]?DMF?5H2O}n(3-3)and{[Cd(Bpybc)(hip)(H2O)]?5.5H2O}n(3-4),through the molecular self-assembly with the bipyridinium ligand Bpybc.The key factors impacting on the photosensitivity and construction regulation were studied from the following aspects:the distance between donor and acceptor,the dihedral angle between the two adjacent pyridine rings and the?–?stacking interaction between bipyridinium ligand.Furthermore,we have explored the thermochromism and solvatochromism abilities of 3-4.(3)Through coordination assemblies with the metal cadmium ion and auxiliary carboxylic acid ligands with substituent group owing different electron-withdrawing/donating ability,two compounds with same structure were constructed{[Cd(Bpybc)0.5(mip)(H2O)]?2H2O}n(3-5),{[Cd(Bpybc)0.5(nip)(H2O)]?H2O}n(3-6).The substituent effect on adjusting the photochromism of viologen-bearing coordination polymers have been studied by comparing different light response behaviors of two isoreticular compounds.And the present work demonstrates a practical way to regulate photochromism of target coordination polymer. |
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