| Coordination polymers(CPs),as one kind of the important inorganic-organic hybrid materials,have been extensively investigated in modern chemistry and materials science research.Among them,crystalline CPs containing olefin ligands have received extensive attention due to their[2+2]cycloaddition reaction,isomerization and changes in chemical and physical properties.The photochemical[2+2]cycloaddition reactions in crystalline CPs can proceed in a highly regio-and/or stereo-specific manner.It can lead to an efficient,specific and simple synthesis of cyclobutane-based products which is hard to be prepared by traditional solution methods.Currently,most studies in this respect are involved in CPs with mono-olefinic ligands,while those containing multi-olefinic ligands are less documented.It is noted that such multi-vinyl ligands within CPs could have more alignments of C=C pairs and achieve more complicated photochemical[2+2]cycloadditions,thus providing more unexpected cyclobutane derivatives.Correspondingly,the precursor CPs and their photoproducts may have more diverse phycochemical properties.Therefore it would be of great importance in exploring photochemical[2+2]cycloaddition reactions within CPs of multi-vinyl pyridyl ligands.In this thesis,we delicately chose three multi-vinyl pyridyl ligands,4-pyr-poly-2-ene(ppene),1,2,4,5-tetrakis(4-pyridylvinyl)benzene(4-tkpvb)and 1,2,4,5-tetrakis(3-pyridylvinyl)benzene(3-tkpvb),and carried out their solvothermal reactions with Zn(Ⅱ)/Cd(Ⅱ)/Ni(Ⅱ)salts and different carboxylic acids to yield a series of multidimensional CPs.The olefinic ligands were aligned in different fashions within these structures and exhibited diverse photoreaction activities.Some CPs were selected to proceed their photochemical reactions and the physicochemical properties before and after the[2+2]cycloaddition were investigated.The detailed results are described as follows:1.Five Cd(Ⅱ)CPs were synthesized based on ligand ppene respectively,including[Cd(ppene)(1,2-BDC)]n(1),[Cd(ppene)(1,3-BDC)]n(2),[{Cd(ppene)(1,4-BDC)}-MeCN]n(3),[{Cd(ppene)(1,3,5-HBTC)}·0.5(ppene)]n(4)and[Cd(ppene)(4,4’-OBA)]n(5).Upon UV light irradiation,1,3 and 4 underwent a double[2+2]cycloaddition reaction to yield new CPs including[Cd2(4-tp-3-lad)(1,2-BDC)2]n(la,4-tp-3-lad=2,3,5,6-tetra(pyridin-4-yl)bicyclo-[2.2.0]hexane),[{Cd2(4-tp-3-lad)(1,4-BDC)2}·2MeCN]n(3 a)and[{Cd2(4-tp-3-lad)(1,3,5-HBTC2}·(ppene)]n(4a)in a single-crystal-to-single-crystal(SCSC)manner.As a representative example,3a was proved to be an efficient probe for dual detection of nitroaromatics and Hg2+ in aqueous solutions.2.Four CPs were synthesized based on ligand 4-tkpvb respectively,including[Cd(4-tkpvb)(1,3-BDC)]n(6),[Cd(4-tkpvb)(1,4-BDC)]n(7),[Zn(4-tkpvb)(1,3,5-HBTC)]n(8)and[Zn(4-tkpvb)(4-IBA)2]n(9).Each 4-tkpvb pair is aligned in different manners within these structures.Upon UV light irradiation,each 4-tkpvb pair underwent[2+2]cycloaddition to yield different cyclobutane-based products.Compounds 6-9 were converted into their corresponding new CPs 6a-9a in a SCSC style.These results demonstrate that CPs with 4-tkpvb can be performed as an excellent synthetic platform for achieving highly regio/stereo-selective[2+2]cycloaddition and preparing diverse cyclobutane-based derivatives.3.Five different CPs were synthesized based on ligand 3-tkpvb respectively,including[Zn(1,4-BDC)(3-tkpvb)]n(10),{[Cd2(4,4’-SDC)2(3-tkpvb)2]·0.5(3-tkpvb)}n(11),[Ni(4,4,-SDC)(3-tkpvb)]n(12),[Ni(1,4-BDC)(3-tkpvb)]n(13)and[Ni(1,4-NDC)(3-tkpvb)(H2O)]n(14).Upon UV light irradiation,10 and 11 underwent photochemical[2+2]cycloaddition reactions to produce new CPs 10a and 11a in a SCSC manner,while 12-14 showed photo-inactive.10 and 11 exhibited strong luminescence while the luminescence intensity of 10a and 11a got reduced.The results disclosed that after[2+2]cycloaddition,the conjugated system of the newly-formed CPs may be changed,which may trigger changes on their luminescent properties.This may provide a special route to the development of new luminescent switching materials.4.Seven 2D/3D CPs were synthesized based on ligand 4-tkpvb respectively,including[Cd(4-tkpvb)(5-tert-BIPA)]n(15),[{Cd(4-tkpvb)(1,3,5-HBTC)}·0.5DMF]n(16),[Cd(4-tkpvb)(1,4-NDC)]n(17),[Cd(4-tkpvb)(NO2-1,4-BDC)]n(18),[Zn(4-tkpvb)(2,5-DBPTA)]n(19),[Zn(4-tkp vb)(3,5-DBBA)2]n(20)and[Zn(4-tkpvb)(4,4’-OBA)]n(21).In the structures of 15-21,the 4-tkpvb pairs showed different alignments but they did not undergo any expected[2+2]cycloaddition reaction upon UV irradiation,though some of them meet the criteria of Schmidt’s rule for a photocycloaddition.It may be ascribed to the configurations of the carboxylic acids and the structures of the CPs employed.Moreover,addition of Hg2+ into the DMF solution of 4-tkpvb greatly changed its colour,which was clearly visible to the naked eyes.The representative compound 15 was confirmed to be an uncommon multi-responsive luminescent sensor for Hg2+,CrO42-and Cr2O72-in water through the luminescence quenching method. |
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