Structural Design, Preparation And Characterization Of The Donor Acceptor Type Photoactive Crystalline Materials Based On Metal Halogen Complexes

Photochromic materials have attracted a lot of attentions for their widely applications,such as optical displays and sensors, decoration, optical switching, artificial photosynthesissystem. Their properties can be tuned by structural design and tailor. However, the research onthe design and construction of new D-A crystalline materials via component selection andstructural control has not been fully explored.The thesis focused on the syntheses of new photoactive crystalline materials that involveelectron transfer. Electron deficient organic viologen components can be combined withelectron rich metal halide units via coordinating with the metal centers. The affecting factorsof photoactive characters, such as metal centers, metal halide units, structural arrangement,different metal centers, have been investigated. The results are listed as follows:1.Two ionic compounds with similar structural motif [Zn Cl4(CNPBPY)]·H2O(compound 1)and [Cu Cl4(CNPBPY)]·H2O(compound 2) are obtained by the reaction ofCNPBPY(N-(3- cyanophenyl)-4,4’-bipyridinium chloride), HCl, H2 O with Zn Cl2 andCu Cl2·2H2O respectively at room temperature. The compound 1 shows remarkablefluorescent-photochromic characters, By comparison, compound 2 is not photoactive. Thedifferent results can be attributed to the structure of metal halide units and the distancebetween the donor and acceptor components.2.Two one dimensional chain Inorganic-organic hybrids compounds{[Cd(CPBPY)Br2]·H2O}n(compound 3) and [Cd(HCPBPY)I3]n(compound 4) have beensynthesized by the hydrothermal reactions. An in situ hydrolysis reaction generates the CPBPYligand from the CNPBPY molecule. The physicochemical characterizations indicate that thesetwo compounds all show interesting fluorescent-photochromic characters. Their differentphotoresponse rates are associated with the electron donating ability and distance of the D-Aunits.3.(CNPBPY)Cd2Cl6·4H2O(compound 5) with binuclear metal chloride unit isobtained by a solvent evaporation process at 298 K. In this complex, the binuclear cadimiumchloride unit acts as electron donor, while the CNPBPY cation is electron acceptor. UV-vischaracterizations show that it is a photochromic complex. Its color changes from brown todark green upon light irradiation, which can be attributed to electron transfer from the electronrich chloride anion to the electron deficient CNPBPY cation.4.Two new supramolecular systems [HCPBPY] [Zn Cl4]·H2O(compound 6) and[Zn(CPBPY)Cl3]·H2O(compound 7) are built by the combination of Zn Cl2 andN-(3-carboxyphenyl)-4,4’-bipyridinium ligands via the solvent evaporation and thesolvothermal method respectively. Single crystal data analyses indicate that 6 is an ioniccomplex while 7 is a coordination complex. Time resolved UV-vis characterizations show thatcompound 7 has a faster photoresposing rate than compound 6. This can be attributed to theirdifferent structural arrangement and distance of the donor and acceptor blocks.