| Stimuli responsive smart materials are materials that can undergo physical or chemical changes under the action of external stimuli(such as mechanical force,light,heat,acid/base,ion,ultrasonic,etc.).They have important application values in drug delivery,fluorescent probe,anti-counterfeiting,pressure sensor,photoelectric device,etc.Among them,organic small molecule compounds,which are sensitive to environmental changes,have been paid much attention because the desired signal output can be easily realized through molecular structure tailoring.It is worth noting that the organic molecules containing large conjugated systems have unique photo-physical properties and may self-assemble into physical gels under the non-covalent bonds,such asπ-πinteraction and van der Waals forces.Hence,the obtained luminescent materials would be more sensitive to environmental changes.In addition,the molecular configuration or conformation of the fluorescent dyes may be changed by the stimuli of external mechanical forces and the molecular packing mode would be also changed.Therefore,they may exhibit piezofluorochromic properties.Although the nitrogen-containing fused heterocyclic units have become an important building block in organic opto-electronic materials,there are few reports on organic functional molecules based on quinazoline and pteridine derivatives.These two kinds of compounds show significant biological or pharmaceutical activities.If they are introduced into the luminescent molecules,it will expand the application of materials in biological systems.Therefore,in this thesis,a series of new indoloquinazoline and pteridine derivatives have been synthesized,and their self-assembling as well as photo-physical properties have been studied.In addition,the fluorescence sensing properties of the synthesized compounds have been investigated.The main results are listed below.New indoloquinazoline derivatives(FIQZ,Cl IQZ,Br IQZ and IIQZ)bearing different kind of halogen have been synthesized.In absence of the traditional gelation groups of hydrogen bond donor and acceptor and long alkyl chain,etc.the four compounds showed good gelation ability in organic solvent.For example,the stable organogels are formed in cyclohexane,acetonitrile,methanol,ethanol and isopropanol.Among them,the lowest critical gelation concentration(CGC)reaches 2.0 mg/m L.The fluorescence emission intensity of FIQZ,Cl IQZ,Br IQZ and IIQZ increased obviously in the process of gel formation,indicating that the molecules show aggregation induced emission(AIE)properties.The synthesized quinazoline derivatives contained alkaline nitrogen atoms,so they can be protonated by acid.Therefore,the fluorescence of the four compounds in solutions decreased gradually with the increase of the concentration of trifluoroacetic acid(TFA).Meanwhile,the color of the solution changed from colorless to yellow.Similarly,the xerogel films based on FIQZ,Cl IQZ,Br IQZ and IIQZ can also be used as fluorescence sensory materials to detect the acid vapors of TFA,hydrochloric acid,nitric acid,sulfuric acid and acetic acid,and the decrease of the emission was observed.The concentration of acid dependent ~1H NMR spectra showed that the acidochromism was orginated from the protonation of indolequinazoline by acid.The pteridine derivatives bearing carbazole,tert-butyl carbazole,triphenylamine and methyltriphenylamine(CPCP,CDBCP,CPDPA and CPDPTA)have been synthesized.They showed piezofluorochromic properties in solid states.It has been found that tert-butylcarbazole-substituted pteridine showed high contrast of piezofluorochromism compared with carbazole-substituted pteridine.On the one hand,it may be due to the strong electron donating ability of tert-butylcarbazole,which will yield strong intramolecular charge transfer(ICT)and lead to more sensitivity to external stimuli.On the other hand,the introduction of tert-butylcarbazole would induce loose molecular packing,which can be easily changed by mechanical force.Hence,the obvious change of fluorescence spectrum would be observed.Similarly,the contrast of piezofluorochromism of methyltriphenylamine-substituted pteridine was higher than that of triphenylamine-substituted pteridine.Under the treatment of grinding and solvent fuming,the pteridine derivatives exhibited reversible piezofluorochromism.The transformation from crystalline state to amorphous state or to the less ordered crystalline state would induce the shift of the emission.The rearrangement of the molecular under the solvent fuming led to the recovery of the emission.This work might extend the application of pteridines in organic functional materials. |
