Synthesis And Characterization Of Photochromic Benzimidazolium Iodoargentate Hybrids

Photochromic materials have aroused widespread attention owing to their potential applications in various high-tech realms,such as protection decoration,optical switching,memory,filtering,display and modulators.Especially,photochromic hybrids based on electron donor-acceptor units are particular interest due to their tunable compositions,structures,and intriguing synergistic effect,which are mainly composed of strong electron acceptors?strong?-acids?such as viologens/NDI derivatives and strong electron donors?Lewis bases?such as chlorometallates,metal cyanides,metallophosphates,zeolites.Recently,several photochromic iodometallates chargely balanced by monocyclic pyridine derivatives?pyrazinium,methylnicotinohydrazide and carbomethoxypyridinium?and benzotriazolium have been reported by our group,which exhibit diverse structures,fast photoresponse and unique photoinduced intermolecular ET as well as simultaneous intermolecular charge transfer?CT?.Additional to the monotonous usage of strong electron donor-acceptor units reasonable selection of new electron donor-acceptor with medium electron accepting ability could be an effective strategy to optimize internal electronic behavior and develop new photochromic hybrid materials.In this thesis,using in situ methylated/protonated benzimidazole,sevenphotochromic iodoargentate hybrids have been synthesized,which exhibit structural diversity,adjustable energy gaps,nonlinear optical properties and typical photosensitivity.On the basis of structural analysis,powder diffraction,electron paramagnetic resonance and UV-vis diffuse reflectance spectroscopy,their structure-property relationship were investigated.Preliminary results are listed as follow:1.Compared with the monocyclic pyridine cations,introduction of weak benzimidazolium can not only obviously improve the photosensitive behavior of iodoargentates but also adjust photochromic mechanism.In other words,in these compounds,the photochromic mechanism from the absence of chromic behaviour to the photolysis of anionic frameworks and dual photolysis and photoinduced secondary ET are realized.2.The photochromic behavior of iodoargentate hybrids directed by protonated/methylation benzimidazole and its derivatives depend on bonding mode and aggregation density of the inorganic moiety.3.[MPBI][Ag₃I₄]shows the dual mechanisms of photolysis for iodoargentate framework and electron transfer of silver nanoparticles as secondary electron donor.