Coordination Polymers With Tetravinyl Pyridine Ligands:Construction,Structures And Photoresponsive Behaviors

Stimuli-responsive materials as a new type of energy conversion materials have recently become a research hot topic.When exposed to external stimuli,these materials can experience dynamic changes in their structures,causing them to go mechanical movement on a macroscopic scale,such as bending,jumping,tursting,cracking and bursting.External stimuli sources include light,magnetic field,electric field,pressure,temperature,humidity,pH,and guest molecules.In recent years,coordination polymers(CPs)with vinyl liagnds have attracted much attention.However,the vinyl ligands are mainly those containing mono-or bi-vinyl groups,which result in the limited alignments of C=C pairs.In fact,only a few vinyl CPs show photoresponsive behaviors upon light irradiation,which would be a big challenge if they are widely applied in the smart devices.In this thesis,a tetravinyl pyridine ligand is used to assemble with Zn(II)and carboxylic acids to prepare a set of vinyl CPs.Their structures and photoresponsive behaviors before and after light irradiation are examined.One representative CP is combined with certain organic polymer to form composite films,which are used to explore their interesting photoactuating behaviors.The main results are described below.1.Three isostructrual one-dimensional(1D)CPs[Zn(tkpvb)(4-Fb)2](Zn1,tkpvb=1,2,4,5-tetrakis(4-pyridylvinyl)benzene,4-HFb=4-florobenzoic acid),[Zn(tkpvb)(4-Cb)2](Zn3,4-HCb=4-chlorobenzoic acid)and[Zn(tkpvb)(4-Bb)2](Zn5,4-HBb=4-bromobenzoic acid)were solvothermally prepared.When exposed to 334 nm-475 nm light,Znl can be transformed into a family of isomeric two-dimensional(2D)CPs[Zn(poly-bpbpvpcb)(4-Fb)2]n(Zn2n,n=a-g)in a single-crystal-to-single-crystal(SCSC)manner.An interesting phenomena,i.e.photoinduced nonlinear lattice expansion,triggered by photo-induced[2+2]cycloaddition was observed.Through the fabrication of 1-PVA composite film(PVA=polyvinyl alcohol),the internal small stress released by the lattice expansion in the above photochemical reaction can be amplified to trigger macroscopic mechanical motions.Three kinds of photoactuating device models were further designed by using such films.When exposed to light,these devices did exhibit apparent and fast mechanical response behaviors.2.Four Zn(Ⅱ)-based CPs including[Zn(4-tkpvb)(FB)2]n(CP1),[Zn(4-tkpvb)(CB)2]n(CP2),[Zn(4-tkpvb)(BB)2]n(CP3)and[Zn(4-tkpvb)(NTP)]n(CP4),were prepared from solvothermal reactions of Zn(NO3)2·6H2O with 4-tkpvb in the presence of 3-florobenzoic acid(HFB),3-chlorobenzoic acid(HCB),3-bromobenzoic acid(HBB)and nitroterephthalic acid(H2NTP).CP1-CP3 has similar 1D zigzag chain structures assembled by 4-tkpvb connecting the[ZnL2](L=FB,CB,BB)units.CP4 displays an unusual 6-fold interpenetrating three-dimensional(3D)net with a dia topology formed by linking the 2D layers[Zn(NTP)(4-tkpvb)]n via 4-tkpvb ligands.As CP3 had strong photoluminescent emission and good water stability,it served as a luminescent sensor to detect Fe3+ and CrO42-in aqueous phase.It worked well with two different luminescent detection mechanisms and exhibited good detection performances.