| The development of supramolecular chemistry has always been inseparable from the synthesis and application of various new macrocyclic hosts.In comparison with the historic traditional macrocyclic molecules(including crown ether,cyclodextrin,calixarene,and cucurbituril),pillar[n]arene is undoubtedly a newcomer to the family of macrocyclic molecules.Pillar[n]arene has been broadly used in many fields,including sensors,catalysis,separation,and biomedicine,owing to its rigid structure,facile synthesis,ease of functionalization,and outstanding host-guest properties.Especially the fluorescent pillar[n]arenes with different sizes of cavities can bind to different types of guests and alter the fluorescence signal in accordance.Therefore,the research works of this dissertation mainly include the synthesis of functionalized fluorescent pillar[n]arenes and its selective detection for amines by using a novel fluorescence enhancement mechanism under host-guest complexation.The main contents are listed as follows:In Chapter 2,a “Supramolecular Cyclization-Induced Emission Enhancement”(SCIEE)strategy for the selective detection of alkanediamines was proposed.This strategy involves introducing multiple binding sites into the molecular structure of the macrocyclic molecules,so that the macrocyclic molecules and specific guests can form a host-guest complex with a ringlike structure through multiple intermolecular interactions.Such a ring-like self-assembly structure restricts the free motion of the macrocyclic molecule,resulting in the fluorescence enhancement and selective recognition.Two quinoline-malononitrile modified pillar[5]arene derivatives H1 and H2 were synthesized successfully,and H2 was designed with three binding sites specifically suited for alkanediamines.The host-guest binding studies of H2 with different guests were performed,and only 1,8-diaminooctane(G8),1,10-diaminodecane(G10),and1,12-diaminododecane(G12)resulted in a significant enhancement of the fluorescence,indicating the selective detection toward them.This is because H2 and these three kinds of alkanediamines can form a host-guest complex with a ring-like structure,and the carboxylamine interactions and van der Waals interactions in the host-guest complex restrict the free motion of H2,resulting in the fluorescence enhancement and selective detection of G8,G10,and G12.H1 has only one binding site,hence it could not detect alkanediamines selectively.This work provides a new strategy to develop the probe with high selectivity and sensitivity.In Chapter 3,two diphenylethene group modified pillar[5]arene derivatives H3 and H4,and another molecule(H5)without pillar[5]arene structure were synthesized for the selective detection of spermine based on the SCIEE mechanism.The introduction of diphenylethene groups allowed H3 and H4 to exhibit excellent dual state emission properties.When nine kinds of biogenic amines were added to H3,the fluorescence emission of H3 was significantly enhanced upon the addition of spermine,while no significant increase in fluorescence was observed in any of the other amine solutions.DFT calculations and independent gradient model(IGM)analysis results revealed that the synergy of multiple weak interactions in the complex played a key role in the selective detection of spermine.The absence of substantial fluorescence enhancement in H4 and H5 indicated their inability to effectively bind with spermine,which was attributed to the great distance between two carboxyl groups of H4 and the lack of a pillar[5]arene cavity in H5.Finally,H3 was successfully used for the detection of spermine in artificial urine.This work presents a novel approach to developing probes for spermine detection,and suggests potential applications in early cancer diagnosis.In Chapter 4,an asymmetrically functionalized pillar[6]arene(H6)was synthesized successfully by fragment coupling method.H6 exhibited a dual emissive fluorescence property resulted from through space charge transfer.Single crystal structure analysis showed that the strong intermolecular interactions restrict the free motion of H6,resulting in strong fluorescence in the aggregated state.When 4,4’-diaminobiphenyl was added to H6,a reciprocal transition between the local excited state(LE state)and the charge transfer excited state(CT state)could be observed.But this phenomenon could not be found upon the addition of other guests,indicating that H6 could be used as a fluorescent sensor for the detection of 4,4’-diaminobiphenyl.H6 could also be used as an adsorbent material for the adsorption of 4,4’-diaminobiphenyl in water.This work represents an innovative attempt to the functional derivatization of pillar[6]arene,and provides a new idea for the synthesis of fluorescent pillar[6]arene in the meantime. |
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