AIE And Mechanofluorochromism Properties Of D-A Polyaryl Ethylene Derivates

Piezfluorochromic materials are a class of―smart‖materials with fluorescentproperties that change in response to external force stimuli, which are dependent onchanges in physical molecular packing modes. These materials arewidely used inoptical storage, mechanical sensors,memory chips and optoelectronic devices. Inrecent years, the researches shows that some compounds are both AIE active andpiezfluorochromism, which draw a lot attention to study the connection between AIEpropery and piezfluorochromism, and made great achievements. The concept ofPiezfluorochromic Aggregation-Induced Emission (PAIE) materials has been broughtforward.Comparing with traditional piezochromic materials, PAIE materials have higherresponse sensitivity and broader scope. And, they have received a lot attention due totheir promising applications in optoelectronic devices, organic field-effect transistorsand sensors, etc. The compounds containingtetraphenylethene or triphenylamine havepromising applications in AIE, OLED, multiple stimulus response, etc.Phenothiazinehas strong electron capacity and hole transport properties, and the functionalmolecules containing phenothiazine can show competitiveness in the field ofoptoelectronic. Moreover, quinoxaline is an important chemical intermediates whichbeen wildly used for fluorescent probe and dyes. So, herein, we mainly focus thesynthesis of a series of functional PAIE molecules from phenothiazine,triphenylamine, quinoxaline and tetraphenylethene and the investigations of their AIEand Piezfluorochromic properties. Some creative results have been obtained, whichwere outlined below:(1) Three new D-π-A conjugated molecules based on tritriphenylacrylonitrile,which was linked to phenothiazine (Donor) in its10-position (P10TPAN) or3-position (P3TPAN) as well as bridged by vinyl (PVTPAN) have been synthesized.Their AIE and Piezfluorochromic properties were studied. The resultsshowed that the three compounds exhibited AIE behaviors and the fluorescencequantum yields of PVTPAN、P3TPAN and P10TPANwere as high as52.9%,45.5%and11.3%, respectively. Upon grinding,PVTPAN, P3TPANand P10TPANshowedsignificant piezfluorochromism with high color contrast. The as-synthesized crystalsof PVTPAN, P3TPANand P10TPAN emitting strong yellow (536nm),yellowish-orange (572nm) and yellowish-green (514nm) light under UV irradiationcould be transferred into powders emitting red (608nm), orange-red (598nm) andorange (568nm), respectively, suggesting the spectral redshifts of72nm，26nm and54nm, respectively. Moreover, we found that the fluorescence quantum yields ofPVTPAN, P3TPANand P10TPANin theground powders are28.9%,36.0%and10.2%, respectively.Suchpiezfluorochromism was reversible upon the treatment ofgrinding and heating/fuming with DCM. Thoseresultsillustrated PVTPAN，P3TPANand P10TPANcould be applied in information storage, detection of volatileorganic compounds and OLED, etc.(2)A series ofnovel D-A-Dtriads composed of two tetraphenylethene and onediphenylquinoxaline/quinoxaline unit in both vertical and horizontal directions havebeen successfully synthesized, called BTPQ, DBTPQand BTBQ, respectively. The itwas found that all luminogens exhibit AIE feature. BTPQ and DBTPQ are not onlyAIE-active, but also shows piezfluorochromic property, upon grinding, their emissionchanges about34nmand16nm, respectively. Moreover, the fluorescence quantumyields of BTPQ and DBTPQ in the as-prepared solid are16.3%and56.2%,respectively. After grinding, the fluorescence quantum yields of BTPQ and DBTPQin the ground powders are29.9%and62.3%. On the other hand, the fluorescencequantum yield ofBTBQ in solid state is60.2%, which is AIE-active but shows nopiezfluorochromic feature.More interestingly, BTBQ shows response to acid vapor,but BTPQ and DBTPQ can not respond to acid vapor.