Carborane-Heterocyclic Compounds:Synthesis And AIE Properties

Solid state luminescent materials are widely used in sensing,biological imaging,information storage and other fields due to their high luminescent efficiency,wide range of luminescent wavelengths and simple preparation.Therefore,the development of efficient solid luminescent materials has important scientific significance and wide application prospects.In recent years,a class of Aggregation-induced emission(AIE)materials containing o-carborane have shown potential application value in optoelectronic devices,biopharmaceuticals,molecular probes and other fields due to their high thermal stability,chemical stability and multi-effect luminescence properties.At present,carbborane AIE materials are mainly compounds containing thick cyclic aromatic hydrocarbon structure,however,and there are still some problems such as low luminous efficiency,small Stokes shift,and difficult to adjust their luminous wavelength and color.This thesis o-carborane was introduced into the heterocyclic compounds such as carbazole,phenothiazine and phenoxazine containing N,S and O heteroatoms.A class of solid state luminescent materials containing heterocycles of o-carborane were constructed by controlling the excited state of compounds through the charge transfer synergistic effect between heteroatoms with different electronegativity and strong electron-absorbing properties of o-carborane.The AIE properties of the compounds were studied to reveal the structure-activity relationship between the types and number of heteroatoms in the aromatic heterocyclic ring and investigate the luminescence properties of the materials.The specific research contents are as followed:(1)Two 9-phenylcarbazole functionalized compounds CBD3 and CBD4 were obtained by introducing o-carborane into different active sites of 9-phenylcarbazole through Ni catalyzed Kumada coupling reaction.The photophysical properties of the compounds were studied.The results showed that both CBD3 and CBD4 had AIE properties,and the quantum yield of CBD3 and CBD4 both reached about 80% in solid state.The theoretical calculation results showed that there is obvious intramolecular charge transfer(ICT)between o-carborane and fluorocarbazole.(2)The compounds CDC,CDO and CDN with different electronegativity were synthesized by introducing fluorene,carbazole and dibenzofuran compounds containing different heteroatoms into o-carborane as fluorescence groups.The structure and properties of the three compounds were tested and characterized.The results showed that all of the three compounds had AIE properties,the emission wavelength was adjustable from 490 nm to 550 nm,and the emission color changed from blue to yellow.The quantum efficiency of the three compounds all reached about 70% in solid state The theoretical calculation results showed that the electronegativity of heteroatoms in the compound molecules was different,which led the significant difference of ICT between the o-carbborane and the fluorescent groupmolecules.(3)A Ni-catalyzed Kumada coupling reaction was used to synthesze the o-carborane compounds CBPNO and CBPNS containing phenothiazine and phenoxazine derivatives.The photophysical properties of CBPNO and CBPNS were characterized.The results showed that the compounds had double emission characteristic in solution and AIE properties.The emission of the compounds in solid state is located in near infrared region and their Stokes shift was up to 350 nm.In solid state,the compounds CBPNO and CBPNS could achieve the foroluminescence enhanced response by force regulation of intramolecular charge transfer,and the response can be restored to the original state by self-repair at room temperature.Theoretical calculation results showed that The theoretical calculation results showed that due to the existence of O atoms and S atoms,the coplanarity of fluorophores was different.Under the stimulation of mechanical force,the molecules of compounds accumulated and their structures distorted,so the luminescence phenomenon of compounds was obviously enhanced under the action of external force.In addition,the distortion of the molecular structure led to the thermodynamic non-equilibrium state of the compound,in which the compound would spontaneously change to a stable structure,thus showing the property of fluorescence self-recovery at room temperature.