Synthesis Of Tetraphenylethylene Macrocycles,Their Aggregation-induced Emission Mechanism And Detection Of TNT Gas

Fluorescent compounds have very important applications in many fields,chemistry,biology and materials included.However,traditional organic fluorescent compounds have notorious concentration quenching effect which greatly restricted the applications in the form of solid materials.The uncover of aggregation-induced emission（AIE）effect in2001 by Tang et al has opened novel concept to design solid state fluorphore.AIE compounds have widespread applications in solid state emission materials and chemical/bio sensors.The mechanism of the AIE effect is complicated due to various types of compounds and different structures can have AIE effect.Some of the proposed mechanisms are also lack of deep understanding and direct evidences.Also,the selectivity of the bio-sensors based on AIE was generally poor.In this thesis,based on the synthesis of the TPE macrocycle compounds,the AIE effects and mechanism as well as the application for TNT gas sensing were studied with fruitful results.1.The propeller-likeconformationoftetraphenylethylene（TPE）with aggregation-induced emission（AIE）effect was partially and completely immobilized by intramolecular cyclization.The immobilization of propeller-like conformation was found to show great advantages in determining the enantiomer purity,recognition of chiral amines.The completely immobilized compound 6 were resolved into M-and P-enantiomer,which showed mirror imaged CD and almost quantitative fluorescence quantum yield.Furthermore,it also showed a mirror and large circularly polarized luminescence dissymmetric factor,which resulted from the helicity of the enantiomer.2.A number of TPE bicyclic compounds were designed and synthesized,especially cis-14 and gem-15 which were isomers with completely same substituents As demonstrated by their photophysical properties,the inhibition of the rotation of double bond at excited state played key role on AIE effect.Due to blocking of free rotation of the double bond in excited state,cis-TPE dicycles emitted much stronger fluorescence than gem-ones.Other rotations,including flapping of phenyl rings of TPE unit and rotation of phenyl bridge showed little effect on the emission.3.TPE macrocyclic compound 20 composed of three pyridinediformyl and three TPE units was synthesized.In the solid state,it forms self-inclusion molecular cage by insertion of pyridyl groups into cavity of the macrocycle adjacent to it.Due to the giant cavity of the macrocycle,the self-inclusion cage formed just by host-guest interactions of two macrocyclic compounds had still big void,which could accommodate two TNT molecules.Even after the TNT and solvent molecules were removed,the void of the cage was still retained and could give permanent pores.These pores could be exploited in both selective absorption of CO₂ and sensor for TNT vapor.4.Foldamers with double hairpin-turn linkers were synthesized by using TPE as folding units and triazine as turn linkers.Due to usage of TPE units with AIE effect as aromatic units in foldamers,they emitted strong fluorescence in aggregation state and showed increased fluorescence quantum yield with increase of number of folded TPE units.The increased fluorescence could be used to detect TNT at several nM concentrations in aqueous solution and even highly diluted TNT vapor in air.The crystal structure of26-TNT complex showed that n-πinteractions and hydrogen bonds between nitro groups of TNT and aromatic rings of foldamers are the key for binding TNT molecules.