The Synthesis And Application Of Aggregation-induced Emission O-carborane-pyrazoline Molecules

Aggregation-induced emission(AIE)compounds exhibit a broad application prospect in the fields of fluorescent biological labels,optical sensors,organic light-emitting diodes(OLEDs)by virtue of their unique photophysical properties.However,compared to the compounds that emit strong fluorescence in the solution but aggregation-caused quenching(ACQ)in the aggregated stated,there are few kinds of AIE molecules with high luminescence quantum yield at present.At the same time,due to complex synthesis processes,unstable structure and single color,the practical application of AIE molecules are limited.Therefore,designing and synthesizing new AIE molecules with high luminescence quantum yield and tunable luminescence has become a hot topic in current research.In this paper,a series of AIE molecules with D-A-D structure are designed and synthesized on the basis of o-carborane and 1,3,5-triaryl-2-pyrazolines(TPP).By testing their photophysical properties,the luminescent mechanism of these compounds was studied and the application of these AIE compounds in the detection of acid and alkali vapor was preliminarily explored.The specific research contents are as follows:1.Designed and synthesised four o-Carborane-1,3,5-triaryl-2-pyrazolines molecules,compounds ST-1,ST-2,ST-3 and ST-4.The basic photophysical properties were characterized by UV-Vis absorption,fluorescence spectroscopy,fluorescence lifetime and quantum yield test.The results show that the compounds display double emission fluorescence in the aggregation or solid state.The short wavelength fluorescence emission peaks belong to the LE state and the long wavelength fluorescence emission peak is ICT luminescence peak.The luminescence mechanism of the compounds was analyzed by the solvent effect experiment,the DFT theoretical calculation and the electrochemical test.The rotation of the adjacent carbon borane molecules and the vibration of the C_c-C_c bond in the o-Carborane were limited.2.Four D-A-D triads compounds CT-1,CT-2,CT-3 and CT-4 were designed and synthesized.The results show that all compounds have AIE properties and high fluorescence quantum yield.The different substituents in the system have obvious effects on the luminescent properties of the compounds,the photoluminescence spectra showed bathochromic shift from 596 to 638 nm.From the solvation effect experiment,time-resolved fluorescence lifetime,X-ray crystallography,CV and DFT theoretical calculations results,the luminescence of the four molecules is attributed to ICT process.The AIE mechanism could be attributed to the restriction of molecular motions and C_c-C_c bond vibration in o-Carborane,the spherical structure of the o-Carborane and the partially torsional TPP molecules obstruct the molecular accumulation of the compounds,it is difficult to form intermolecular?-?interaction between molecules.3.The fluorescent test paper containing compound CT-1,CT-2,CT-3 and CT-4was prepared by a simple impregnation method.The experimental results showed that the compounds had different degrees fluorescence quenching with acid vapor.The trifluoroacetic acid vapor could be completely quench the fluorescence of compounds,the response time is short,the fluorescence quenching efficiency of the compounds is close to 100%.The alkali vapor can be recover the fluorescence of compounds to a certain extent,the reversible conversion between fluorescent switches is achieved by the fluorescence of compounds.