Synthesis And Characterization Of Some Novel D-A Type Photochromic Crystal Materials Based On Metal-ligand-complexes

As one category of functional materials, photochromic materials with special propertiesare one of interesting research fields for its wide application in information storage, solarenergy utilization, optical switch and monitor manufacture.In this thesis, with ligand-based photochromic crystal materials as the subject ofresearch, photochromic functional materials are constructed by using viologen compoundsCNPBPYCl(CNPBPY=N-(3-cynaophenyl)-4,4’-bipyridinium) andTPT(2,4,6-tris(4-pyridyl)-1,3,5-triazine) as electron acceptor ligands, carboxylates andchlorides as electron donor ligands. The acceptor and donor ligands are connected by Zn2+.The influence of different combination of ligands and frame structures on the properties ofmaterials are investigated through the characterization, analyses and comparison of thesynthesized materials. The main results are listed as follows:1. A new one-dimensional chain-like compound [Zn(m-BDC)(CNPBPY)Cl]2H2O(compound1) is synthesized by employing CNPBPYCl and m-BDC as ligands. Theconnections between the zinc centers and m-BDC ligands create the main chain of thecomplex, while the CNPBPY molecules are introduced to the functional system as side groups.The color of compound1turns from yellow to brown-green upon light irradiation andcompound1emits intense fluorescence upon375nm ultraviolet light irradiation.2. A new one-dimensional MOF compound [Zn2(p-BDC)2(CNPBPY)2Cl2] H2O(compound2) is prepared via using viologen CNPBPYCl, p-BDC as ligands. In the structureof compound2, the connections between the zinc centers and p-BDC generate a zigzag chain,while the CNPBPY molecules are alternately distributed in both sides of the chain as sidegroups. Compound2turns from yellow to deep green upon light irradiation and returns toyellow upon heating, demonstrating the process is reversible. TG and XRD date shows thatthe framework is stable up to300℃, suggesting good thermal stability of compound2.3. Two zero-dimensional supramolecular compounds [Zn2(TPT)Cl6]2TPT4(NO3)2H2O(compound3) and [Zn2(NO3)Cl7]2TPT2(NO3)(compound4) are built with TPT and Cl-asligands. The asymmetric unit of compound3is different from that of compound4. In theasymmetric unit of3, zinc centers coordinates with TPT molecules and Cl－, while in the asymmetric unit of4, TPT molecules is not coordinated with zinc centers. Both compound3and4exhibit photochromism upon light irradiation. However the degree of color change of3upon photo irradiation is better than that of4, supported by the UV-vis kinetic rate and thefluorescent quenching rate.