The Study Of The Synthesis And Properties Of New Type Containing Polycyclic Aromatic Asymmetric Diarylethene

Due to the potential applications in optical memories, optical switches, andfull-displays, functional organic photochromic materials have attracted a lot ofattentions. Among many known photochromic systems, diarylethenes are one of themost promising candidates for optoelectronic devices because of their excellentthermal stability and good fatigue resistance. Currently, development of noveldiarylethenes as well as investigation of their structure activity relationship are bothfundamental research and hotspots.In this thesis, three kinds of new asymmetrical diarylethenes with different arylmoieties were synthesized and their optoelectronic properties were investigatedsystematically, especially the effects of fused ring. The main research results areshown as follow:1. Eighteen new asymmetrical diarylethenes were synthesized and theirstructures were identified by NMR, IR and elemental analysis. Four diarylethenecrystals were prepared.2. The photochromic properties of these diarylethene derivatives wereinvestigated in some different media, such as solution, PMMA films. We also studiedthe effects of the fused ring. The results revealed that the effects of fused ring had asignificant effect on the properties of these diarylethenes.3. All of the diarylethenes were thermal stubce in hexane at room temperature.But at80oC, tulargiur their fused rings are, the better the thermal stability ofdiarylethenes are. The fatigue resistance of diarylethenes DT-3、 DT-8~9andDT-16~18was much stronger than other compounds, especially in PMMA amorphousfilm. After200repeated cycles, diarylethenes DT-3、DT-8~9and DT-16~18stillshowed good photochromism with the absorbance above85%.4. The fluorescence spectra of diarylethenes and effects of aromatic heterocyclieshave been investigated both in hexane and in PMMA amorphous film. The resultsshowed that the open-ring isomers exhibited relatively strong fluorescence, while theclosed-ring isomers weaker fluorescence. The relative fluorescence intensity increaseddramatically with the increase of the concentration. But when the concentrationincreased to5.0×10-4mol/L, the fluorescence intensity decrease begin to remarkably.Furthermore, diarylethenes DT-3, DT-8~9and DT-16~18exhibited strong intensity offluorescence emission in both hexane solution and in PMMA films. In addition, in diarylethene systems bearing heteroaromatic rings and condensed moieties,electron-donating substituent could effectively decrease the fluorescence emission anda fluorescence quantum yield. In diarylethene systems bearing a pyrrole moiety, theelectron-withdrawing cyano group improved the fluorescence quantum yields andshifted the emission peak to longer wavelengths.