Investigation On The Synthesis And Properties Of E/Z Isomers Of Tetraphenylethene-based Stilbene Compounds

Organic luminescent materials is of great significance due to their broad applications in various fields,such as fluorescent sensors,stimuli responses materials and organic light emitting diodes.In the aggregate state,conventional luminescent materials may show reduced emission,in comparation to their dilute solutions.The phenomenon is aggregation caused quenching(ACQ).The introduction of aggregation-induced emmission(AIE)has brought hope to efficient solid luminescent materials.Tetraphenylethene(TPE),as a famed AIEgen,has been researched widely due to its simplified sythetic routes and excellent AIE performance.Trans-cis or E/Z isomerization is a mechanism of great importance.The different geometry structure of trans and cis isomers may lead to different properties.In this paper,the new system of TPE-based stilbene compunds was constructed through introducing TPE on stilbene and 6 pairs of trans-cis isomers were sythesized.AIE,piezochromic phenomena,TICT and other mechanisms were researched and influence of trans-cis isomerization on properties of compounds was dicussed.The research contents are as follows:1.TPE was introduced on the position of a benzene ring of stilbene.Meanwhile,methoxy,tert-butyl and cyanogroup were introduced on another benzene ring of stilbene.4 pairs of trans-cis isomers consist of(Z)-TPE-S and(E)-TPE-S,(Z)-TPE-MS and(E)-TPE-MS,(Z)-TPE-TS and(E)-TPE-TS,(Z)-TPE-SBN and(E)-TPE-SBN weresythesized.All the trans isomers have higher fluorescence quantum yields compared to their cis isomers in the solid state obviously.(E)-TPE-MS and(E)-TPE-TS have a high fluorescence quantum yields of 87.72% and 91.68%.Compared to the fluorescence emissions of(E)-TPE-MS,(E)-TPE-TS and(E)-TPE-SBN,the emissions of(Z)-TPE-MS,(Z)-TPE-TS and(Z)-TPE-SBN were red shifted obviously.The crystal packing of(Z)-TPE-S is tight and crystal structure shows(Z)-TPE-S approximates to H-aggregates.The crystal packing of(E)-TPE-TS and(E)-TPE-SBN is lossen and these two trans isomers were J-aggregates under the influence of alkyl chain,heteroatom and trans isomerization.(E)-TPE-MS and(E)-TPE-TS have obvious reversible piezochromic properties.(E)-TPE-TS in powder state has a red shifted fluorescence emission wavelength of 25 nm and a high contrast before and after grinding.However,their cis isomers of(Z)-TPE-MS and(Z)-TPE-TS almost have no piezochromic phenomena.Moreover(E)-TPE-SBN also have obvious piezochromic properties.According to the analysis of PXRD data,the piezochromic phenomena of these compounds is caused by the change from the crystalline state to the amorphous state.The lacks of piezochromic phenomena of(Z)-TPE-MS and(Z)-TPE-TS were caused by the difficulty on destroying the crystalline structure of cis isomers.2.TPE was introduced on 4-position of two benzene rings of stilbene.A system of TPE-based stilbene compounds with lager conjugation was constructed and(Z)-BTPPE and(E)-BTPPE were sythesized.(E)-BTPPE has higher fluorescence quantum yields compared to(Z)-BTPPE in the solid state obviously.But fluorescence quantum yields of(Z)-BTPPE and(E)-BTPPE were reduced compared to compounds of last chapter due to enhanced ?-? stacking caused by excessively extended conjugation.The fluorescence emissions of pristine(Z)-BTPPE and(E)-BTPPE are similar but(E)-BTPPE has a obvious piezochromic phenomenon.Pristine(E)-BTPPE has a red shifted fluorescence emission wavelength of 22 nm after grinding and a blue shifted emission of 15 nm after recrystallization.Piezochromic phenomenon of(Z)-BTPPE is unconspicuous.PXRD date and analysis of DSC suggested that(E)-BTPPE was conversed from crystalline state to the amorphous state after grinding.Moreover,the packing of(Z)-BTPPE molecule changed slightly after grinding.It's the reason of the difference in piezochromic phenomena between(Z)-BTPPE and(E)-BTPPE.3.TPE was introduced on the position of a benzene ring of stilbene.Meanwhile,nitryl was introduced on another benzene ring of stilbene.A system of TPE-based stilbene compounds with D-A structure was constructed and(Z)-TPE-NS and(E)-TPE-NS were sythesized.Both two compounds obtained AIE,TICT and solvatorchromic properties.(Z)-TPE-NS and(E)-TPE-NS display dramatically “on-off-on” optical switching property during the research of their AIE properties.We try to make use of two compounds as fluorescence probes detecting trace water in orgnic solvents by utlizing their TICT properties.According to titrimetric analysis of water on two compounds solution in THF and ethyl acetate,the calibration equations of fluorescence emission intensity and amounts of trace water were obtianed.And detection limit and quantitation limit were obtained through caculation.