Synthesis And Application Of Aggregation Induced Emission Mechanofluorochromic Materials Based On Pyrone

Environmental stimuli responsive fluorescent materials have attracted intensive attention by virtue of their promising applications in chemical sensing,bio-sensing,pressure sensing,information storage,photoelectronic devices and drug delivery etc.Since the finding of aggregation induced emission phenomena,design and synthesis of novel AIE molecules,and study on the relationship between their packing mode and stimuli responsive behavior have become a hotspot.Therefore,a series of 2,6-dimethyl-4-pyrone derivatives were designed and synthesized by modification of their donor and acceptor structures in this paper.Moreover,their AIE effect,solvatochromic property and mechanofluorochromic(MFC)behavior were examined systematically by necessary characterizations and the relationship between their packing mode and the above properties were investigated by density functional theory calculation.(1)Three series of D-?-A pyrone derivatives OASPs,PASPs and ANPs were designed and synthesized and the impact of the carbon chain length and substituted position on their electron donor unit to their fluorescent behaviors were comparatively investigated.It was found that all of them exhibited aggregation induced emission enhancement(AIEE)effect,solvatochromic and mechanofluorochromic(MFC)characters,in which,PASP-12 exhibit a 23 nm red-shifted MFC behavior.Meanwhile,all the ground states can recovered completely or partly to their original states through an annealing process.The above results indicate that chain length and substituted position exert a big influence on their fluorescent behaviors.(2)Based on the above work,a series of pyrone derivatives(pp-s)were designed and synthesized by regulating their conjugation degree and the structure of electron donor unit.It was found that all of them displayed aggregation induced emission enhancement(AIEE)phenomenon,solvatochromic property and MFC behavior.Particularly,pp-3 exhibited a superior color-changing effect on account of the explicit triphenylamine group which is the key element for showcasing the enhanced ICT process and charge separation degree.PXRD results further demonstrated the great impact of molecular packing mode on their fluorescent properties.(3)A multi-responsive pyrone compound(CYQ)was synthesized by introduction of indene diketone building block into our parent framework pp-3.Compared with pp-3,CYQ exhibited superior solvatochromic and MFC characters,its PL spectra were found with a 100 nm and 37 nm red-shift,respectively.Powder wide-angle X-ray diffraction(PXRD)and differential scanning calorimetry(DSC)measurements were performed to demonstrate the transformation from the crystalline to amorphous states upon grinding.Besides,CYQ displayed a rapid response to trace water in organic solvents with an excellent water detection limit as low as 0.0096% in tetrahydrofuran(THF).Furthermore,it was found that the fluorescent intensity of CYQ declined linearly upon humidity rise and display promising prospects to become an environmental humidity probe.