Design,Synthesis And Characterization Of Nonconventional Luminogens In Dilute Solutions With Efficient Emission

Nonconventional luminogens are of great interest in traditional fields because of their bright fluorescence or phosphorescence emission at high concentrations.However,most of the reported nonconventional luminogens materials exhibit low fluorescence quantum yields in dilute solution state,which limits the application of nonconventional luminogens.In this paper,we propose the design of heterostructured enamine nonconventional luminogens based on intramolecular hydrogen bonding construction,and find that this strategy possesses several theoretical advantages that are different from traditional CTE(Cluster aggregation induced luminescence)fluorescent compounds through density flooding theory;traditional CTE materials are usually dominated by jumping,and their luminescence mode relies heavily on the spatial conjugation effect caused by the electron-rich aggregation and the local unstable hole electron formation by weak interactions.migration.Most of the CTE materials can only emit light at high concentrations,some of them even reach 8 mol/L.The nonconventional luminogens based on stable enamine structures obtained through molecular structure design change the π-dominated leap to π-dominated leap in the electronic grouping,which greatly improves the molar extinction coefficient and the vibrational intensity of the molecule during the leap from the ground state to the excited state,inducing the molecule to enhance the probability of the formation of the excited state.At the same time,the transition from the excited state to the ground state will also lead to a reduction in the probability of triplet exciton generation through inter-system scramble to improve the utilization of the singlet exciton.In this work,we also introduced push-pull electron groups on the single side of the molecular hydroxyl group through the innovative design of the molecular structure,and the strong polarization of the group will lead to the increase of the molecular dipole moment and split the hole-charge pair region in the overall electrostatic potential of the molecule,which will artificially build the electron leap path in the molecule and strongly induce the radial leap between the ground state excited states,thus significantly increasing the leap efficiency of the molecule.efficiency.Finally,we introduced methoxy and amino groups to form stable intramolecular hydrogen bonds in the construction of the enamine structure,and this structural design can greatly enhance the stability of the branched chains and make the molecular rigidity significantly stronger.At the same time,the C=C double bond in the quinone structure can promote the molecular conformation planarization,so that the excited molecule can not change the molecular conformation even under the impact of highly polar solvent,and then improve the luminescence efficiency.By applying a series of molecular design tools,the quantum yield of the nonconventional luminogens was finally increased significantly from 10% to 86%.And the nonconventional luminogens were extended for applications such as bio-lysosomal fluorescent probes and p H-sensitive fluorescence detection.We believe this work will greatly advance the design of more novel nonconventional luminogens.