Synthesis And Properties Of Asymmetricaldiarylethenes Based On Schiff Base Compounds

Photochromic compounds have attracted much attention because of their potential for applications to optical memories, switching devices and chemical sensors. Among the photochromic compounds, diarylethenes are regarded as the best candidates for the applications, because they have the thermal stability of both their isomers and fatigue resistance while they undergo reversible cyclization/cycloreversion reactions upon irradiation with UV and visible light. It is a hot topic in current chemical research to develop multiple responsive switching molecular systems for diarylethenes that integrate several switchable functions into a single molecule in order to miniaturize the components of machinery and electronics down to the molecular level. It has attracted extensive attention to the design and synthesise of novel water-soluble diarylethenes.In this thesis, sixteen asymmetrical photochromic Schiff base diarylethenes were synthesized. Two different kinds of schiff base were introduced to a diarylethene skeleton for the first time. Their structures were characterized by NMR, UV and IR. The substituent effects on their optoelectronic properties were investigated in detail. This paper mainly studied the impact of different aromatic heterocyclic and benzene ring on the properties of diarylethenes. The main contents and results are generalized as follow:In chapter1, the basic concept, principle, and classification of photochromic compounds are expounded. The application and latest progress of diarylethenes are intensively introduced.In chapter2, the Schiff base diarylethenes of DT-1-5were designed and synthesized. All of these diarylethenes exhibited good photochromic properties in acetonitrile solution. And they have obvious response to sodium hydroxide in acetonitrile solution and they can recover to its initial state via adding the hydrochloric acid. By the stimulation of sodium hydroxide, the absorption maximum of its closed-ring isomers showed extraordinarily large redshift, accompanied with a notable color change. Subsequent irradiation with420nm visible light further caused dramatic changes in theirs colors due to the formation of the benzoxazole moiety. Moreover, the deprotonated open-ring isomers exhibited typical photochromism via the diarylethene intermediate with a benzoxazole unit. The newly formed compounds with the benzoxazole moiety also have photochromic properties.In chapter3, diarylethenes DT-6-9were designed and synthesized. All of these diarylethenes exhibited good photochromic properties in methanol solution. In methanol solution they also have obvious response to the sodium hydroxide, and they can recover to its initial state via adding the hydrochloric acid. By the stimulation of sodium hydroxide, the absorption maximum of its open-ring isomers showed extraordinarily large redshift, accompanied with a notable color change from colorless to yellow. Subsequent irradiation with297nm light further caused a dramatic change in its structure transformation from the sodium phenol compounds to the phenol compounds. In the same way, the close-ring isomers after adding sodium hydroxide under the irradiation of visible light can also transform from the sodium phenol compounds to the phenol compounds. Moreover, upon addition of metal ions indicating the compound have selective interaction with Sn2+.In chapter4, diarylethenes DT-10-16were designed and synthesized. All of these diarylethenes exhibited good photochromic properties in acetonitrile solution. And the open-ring isomers in acetonitrile solution have obvious response to trifluoroacetic acid; a new absorption peak around430nm appeared and increased with the increase of the amount of trifluoroacetic acid.