Syntheses And Properties Of TPE-based Aie-active Derivatives

Luminescent organic materials exhibiting variable and switchable solid-state fluorescence have attracted great attention due to their potential applications in the fields of reversible writing and data storage.In particular,mechanochromic fluorescent materials responding to external mechanical stimuli,which can be applied to mechanical force-sensing systerns,have obtained an increasing amount of attention.Lightful solid-state luminescence and a remarkable color contrast are significant to prepare highly efficiency mechanochromism materials.However,many traditional fluorescent materials suffer from the influence of aggregation caused quenching(ACQ)phenomenon,which leads to a poor condensed phase emission efficiency.Fortunately,in 2001,Tang et al.reported an important aggregation-induced emission(AIE)phenomenon.Luminogens with AIE effect are hardly emissive in dilute solutions,but luminous intensity increased obviously when aggregated into concentrated state.Hence,it is beneficial to acquire high-contrast mechanochromic fluorescent materials.It is well-known that tetraphenylethene(TPE)is a typical AIE unit,and lots of TPE-based derivatives have been shown to be AIE-active.Therefore,it is a significative research topic to design and synthesize mechanofluorochromic luminogens with TPE unit.In this paper,we designed and synthesized a series of TPE derivatives with AIE and mechanochromic behaviors.In addition,we not only synthesized the fluorescent molecules which have self-recovering mechanofluorochromic characteristics without using any external stimuli,but obtained a TPE-modified compound containing carbazole-based skeletons with high fluorescence quantum yield via rational design.The main research contents are as follows:1.Two TPE-based compounds containing cyanobenzene of ortho-position and meta-position isomer units were designed and synthesized.The research results indicated that the target molecules I-1 and I-2 showed aggregation induced emissionand mechanofluorochromic properties,and both of the compounds can recover to the original color autonomously within 10 min after mechanical grinding without using any external stimuli.2.Three TPE-based compounds with different electron effect substituents were designed and synthesized.The research results indicated that these compounds II-1,II-2 and II-3 all showed obvious aggregation-induced emission(AIE)property and the three compounds with different substituents showed different levels of blue and green fluorescence respectively before and after grinding.Furthermore,after these ground solid powders were treated with acetone vapor,these ground powders could revert to their original emission colors.Fortunately,the compound containing trifluoromethyl substituent can recover to the original color autonomously within 2 h after mechanical grinding without using any external stimuli.3.Three carbazole-based compounds containing double TPE and different substituents units were designed and synthesized.The research results indicated that the compounds III-1,III-2 and III-3 all showed obvious aggregation-induced emission(AIE)property and the three compounds with different substituents showed different fluorescent colors before grinding and become the same green fluorescence after grinding.Furthermore,handled with dichloromethane vapor,these ground powders could revert to their as-synthesizd emission colors.In addition,the three target compounds have good thermal stability characteristic according to their initial thermal decomposition temperature which is up to 500? via thermogravimetry.