Synthesis Of Novel Barbituric Acid Derivatives And Its Aggregation-Inducing Emission Properties

The phenomenon of aggregation-induced fluorescence(AIE)refers to the fact that molecules that do not emit light or emit weak light in a solution state can emit strong fluorescence in a state of aggregation,which was first reported by Tang Benzhong in 2001.Due to its special properties,it has great potential application value in the fields of optoelectronics,biotechnology,sensing,medicine,electroluminescent devices and so on.Many research groups have successively invested in the research of AIE active materials,and successfully designed and synthesized many AIE active molecules.However,the currently reported AIE active molecules have a large emission wavelength in the blue and green range,and less in the red and near red ranges,which greatly limits the practical application.In order to extend to low energy illumination regions,covering a wider range of illumination,it is desirable to develop AIE active molecules with red and near red emission wavelengths.In this paper,the optical properties and piezochromism of barbituric acid derivatives with AIE activity are further explored.In the conjugated molecule,barbituric acid acts as a strong electron acceptor(A),and an aromatic ring such as thiophene or furan is introduced as a strong electron donor(D),which raises the HOMO level and lowers the LUMO level,thereby obtaining a narrow band gap.Long-wave emission of AIE active compounds.Five compounds of D-?-A type AIE activity characteristics were successfully synthesized and characterized by the Novenger reaction and the Suzuki reaction.The optical properties of the series of compounds in different states were systematically studied,and the mechanism of fluorescence emission enhancement of AIE active compounds was explored.The size and morphology of the nanoparticles were investigated by dynamic light scattering(DLS)and scanning electron microscopy(SEM).This series of AIE-active compounds was confirmed to have significant piezochromic(MFC)characteristics by grinding the compound powder with a mortar and then fuming it with methylene chloride gas for a certain period of time.Studies have found that this force-chromic property is highly reversible.By analyzing the powder XRD data,it is explained that these compounds can be switched between crystallization and amorphous under external force stimulation.The grounded emission wavelength of the powder is red-shifted with a color change visible to the naked eye.In order to further explore the MFC properties of AIE molecules and explore their response to nitroaromatic picric acid(PA),two non-planar compounds CB and TB were successfully designed and synthesized.The two compounds have similar molecular structures,the molecular masses are almost the same,and the molecular properties vary widely.The compounds CB and TB both exhibited nano-aggregates in a mixed solvent of water and tetrahydrofuran.Both compounds exhibited significant MFC properties by both milling and methylene chloride fuming.The XRD test also confirmed the transition of the two compounds between an ordered crystalline state and a disordered amorphous state.In addition,the two compounds responded to nitroarene explosive PA,and the quenching efficiencies of CB and TB were 48.48 % and 78.13 %,respectively.In summary,the optical properties of different series of AIE active compounds in design and nuclear magnetics were compared and systematically explored and explained.