Synthesis And Properties Of Coordination Polymers Based On Diene Ligands

Coordination Polymer(CP)is a class of coordination compound continuously extending in 1,2 or 3 dimensions through coordination bonds.CPs have wide potential applications in catalysis,adsorption,sensing,magnetism,fluorescence,drug delivery,photoactuator devices,etc.,thus attracting much attention.In this thesis,we employed two diene ligands 1,4-bis((E)-2-(pyridin-4-yl)vinyl)benzene(1,4-bpeb)and 5-fluoro-1,3-bis[2-(4-pyridyl)ethenyl]benzene(5-F-1,3-bpeb)to react with various carboxylic acids and metal salts(Zn(NO3)2·6H2O and Cd(NO3)2·4H2O)under the solvothermal reaction conditions.A series of CPs with different structures were obtained and their structures were characterized by using elemental analyses(EA),IR,thermogravimetric analysis(TGA),powder X-ray diffraction(PXRD),nuclear magnetic resonance(NMR)and single crystal X-ray diffraction(SCXRD).In addition,we examined the adsorption,photosalient behavior and fluorescent properties of these CPs.The primary results are described as follows:1.The solvothermal reactions of 1,4-bpeb,Zn(NO3)2·6H2O,and 1,3,5-H3BTC gave a one-dimensional(1D)chain-like coordination polymer {[1,4-bpebH2][Zn(H2O)(1,3,5-HBTC)(?-1,3,5-HBTC)]·2H2O}n(1)with free cationic ions[1,4-bpebH2]2+between the chains.Interestingly,1 gave rise to another 1D ladder-type coordination polymer {[1,4-bpebH2][Zn(1,3,5-HBTC)(?,?,?-?3-1,3,5-HBTC)]·1.5H2O}n(2)via a single-crystal-to-single-crystal transformation under heating.Both 1 and 2 exhibited great sorption performance towards Congo Red(CR)in water and the maximum absorption capacity of 2(2320 mg·g-1)was increased compared to that of 1(2020 mg·g-1).Thus 2 can be used as an efficient adsorbent for Congo red and showed a great potential in protecting the water environment.2.The solvothermal reactions of 5-F-1,3-bpeb with Cd(NO3)2·4H2O,2,6-H2NDC,4,4-H2OBA or 1,3,5-H3BDC produced three coordination polymers:[Cd(5-F-1,3-bpeb)(2,6-NDC)(H2O)]n(3),[Cd(5-F-1,3-bpeb)(4,4-OBA)(H2O)0.5]n(4),and[Cd(5-F-1,3,bpeb)(1,3,5-H3BDC)]n(5),respectively.Under UV light irradiation,significant changes were observed on their crystal surface.Among them,the crystals of 5 exhibited a drastic photosalient behavior(splitting,bursting,hopping).According to their X-ray analysis,relative to that of 5,there were some changes in the structure of the photoproduct[Cd(bpbpvfpcb)(1,3,5-H3BDC)]n(bpbpvfpcb=1,3-bis-(4-pyridyl)-2,4-bis[3-{2-(4-pyridyl)-vinyl-5-fluoro}phenylcyclobutane](6),which could lead to the photosalient behavior.The above results may be used for the design of novel CP-based photoactuators.3.A 3D CP[Cd(5-F-1,3-bpeb)(1,4-BDC)]n(7)was obtained through the solvothermal reaction of 5-F-1,3-bpeb with Cd(NO3)2·4H2O and 1,4-H2BDC.Upon UV light irradiation,the 5-F-1,3-bpeb ligands in 7 underwent[2+2]photocycloaddition via a single-crystal-to-single-crystal manner,producing{Cd2(dftpmcp)(1,4-BDC)2}n(dftpmcp=3,4,12,13-tetrakis(4-pyridyl)-8,17-bisfluoro-1,2,9,10-diethano[2.2]metacyclophane)(8).During the course of a[2+2]cycloaddition from 7 to 8,we observed the fluorescence of the crystals of 7 was gradually enhanced and then got decreased.When 7 was transformed into 8 completely,the fluorescence of the latter was almost quenched.Such a dynamic fluorescence phenomenon was not reported before.We have also performed DFT calculations to preliminarily explore the possible mechanism for this luminescence change.