Construction And Performance Study Of Hybrid Photochromic Materials Based On Rigid Multidentate N Ligand

Crystalline hybrid photochromic materials（CHPMs）not only possess the intrinsic characteristics of photochromic materials,but also can generate new photo-responsive functions through the synergistic effect between structural components.The intrinsic crystalline characteristic of CHPMs have unique advantages in elucidating the structure-property relationship,which provides the possibility to explore the underlying photo-responsive mechanism.Hitherto,most of the reported CHPMs are synthesized based on photoactive units.The number and types of CHPM-systems based on non-photoactive units are relatively rare.The development of new CHPMs based on non-photoactive units is of great significance for basic research and practical applications.This dissertation focuses on exploring new systems of CHPMs based on non-photochromic units.Based on the mechanism of photoinduced electron transfer（ET）,the rigidπ-electron acceptor（π-EA）units are introduced into suitable electron donor（ED）systems to construct hybrid ED-EA structures with the goal of studying the photo-responsive properties of the target products,summarizing the assembly rules,and clarifying the relationship between the microscopic functional structural units and the macroscopic photo-responsive properties.（1）Based on the mechanism of photoinduced ligand-to-ligand ET and the coordination-driven assembly or template synthesis strategy,coplanar phenanthroline（phen）and its derivative units as EAs were introduced into metal chloride systems to construct a series of CHPMs:[Zn Cl₂（phen）]（1）,[Cd Cl₂（phen）]（2）,[Pb Cl₂（phen）]（3）,[Zn Cl（H₂O）（5-Cl-phen）₂]Cl 2H₂O（4）,[Cd₂Cl₄（5-Cl-phen）₂]（5）,[Pb₂Cl₄（5-Cl-phen）₂]（6）,[H-phen][Bi Cl₄]（7）,[H-5-Cl-phen][Bi Cl₄]H₂O（8）,[H-5-NH₂-phen][Bi Cl₄]·H₂O（9）.Among them,complexes 1 and 4 are discrete structures,and complexes 2,3,5and 6 are one-dimensional chain structures.Complexes 7-9 share the same inorganic anionic chain,with the main difference in the protonated organic guest.Under the irradiation of 300 W Xenon lamp,all complexes show eye-detectable coloration.The discoloration mechanism of complexes 1-6 is attributable to metal-assisted ligand-to-ligand electron transfer,while the photocoloration mechanism of 7-9 is ascribable to hydrogen-bond-assisted ligand-to-ligand ET.The tunable photochromic performance of the targeted product was available via changing the type of the attached group for phen.（2）.Considering the coordination similarity between polyimidazole-based ligands and polypyridine-based ligands,the potential rigid polyimidazole EA unit3,3’,5,5’-tetrakis（1H-imidazol-1-yl）-1,1’-dibiphenyl（TIBP）was introduced into an electron-rich metal-hydroxyethylidene diphosphonic acid（H₄-HEDP）system to construct hybrid chained structures[H₄-TIBP]_0.5[Ln（H-HEDP）（H₂-HEDP）]·n H₂O（Ln=10-Dy,n=1;Ln=10-Eu,n=5;）、[H₄-TIBP][In（H-HEDP）（H₂-HEDP）₂]·3H₂O（11）and[H₄-TIBP][La₂Li（H₂-HEDP）₄（H-HEDP）]·3H₂O（12）with discrete structures.In10-Dy,10-Eu,and 12,phosphonate ligands bridge/chelate metal ions to form chains structure,and the protonated organic ligands TIBP and water molecules as guests locate in the interchain void.Complex 11 has a mononuclear anionic structure with protonated TIBP units to balance the charge.Under the illumination of 300 W Xe-lamp,all the as-synthesized hybrid phosphonate samples showed naked-eye coloration.10-Dy has multiple photo-responsive properties such as photochromism,photomagnetism,photo-modulated fluorescence and proton conduction.Accompanied by photochromism,the maximum fluorescent emission peaks of complexes 11 and 12have obvious red shift phenomenon.The structural comparison analysis before and after the photoirradiation shows that the fluorescence red shift is driven by the configuration change of organic TIBP units.