dc.description.abstract | Organic fluorescent materials have received significant attention in recent years due to their unique photophysical properties. Fluorescent conjugated molecules are widely used in various fields such as bioprocesses and environmental science due to their non-invasiveness, sensitivity, simplicity, and fast response. They find applications in chemical sensors and biological imaging in solution phase, as well as in organic light-emitting diodes and active layers of solar cells in solid-state. Considering that electron transitions to the excited state in fluorescent molecules can occur through both single-photon and multi-photon absorption processes, achieving good performance in both single-photon and multi-photon absorption can expand their applications. Organic dual-state fluorescence emission is a novel research topic, referring to molecules that exhibit fluorescence in both solution and solid-state. This phenomenon was once considered rare due to several competing non-radiative factors in both solution and solid phases, requiring a delicate balance between these competing factors through appropriate molecular design. The importance of developing dual-state fluorescence and multi-photon absorbing molecules lies in the fact that the same molecule can be used for different purposes, significantly increasing the usefulness of fluorescent materials in applications.
Based on previous research and literature search, this study developed fluorescent molecules based on benzotriazole and triazole structural units, focusing on their linear optical measurements of absorption and fluorescence spectra in solution and solid-state, as well as their two-photon absorption spectra in solution within femtosecond regime. The introduction of morpholine functional groups in some of the molecules was found to enable the labeling of lysosomes in cell experiments, demonstrating the potential of such molecules for biological imaging. Among them, model molecule 3 is capable of labeling lysosomes in cells with better specificity and exhibits the highest quantum yield in solid-state fluorescence emission (ФF = 0.44), showing potential as a dual-state emitting material. Model molecule 2 also demonstrates good quantum yields in both solution and solid-state, with ФTHF = 0.96 and ФSolid-state = 0.35, respectively. Additionally, it exhibits strong two-photon absorption with a high absorption cross-section (δ = 495 GM), making it a promising candidate for efficient two-photon fluorescence material.
In addition, we also tentatively explore the synthesis and separation of structural isomers of alkylated benzotriazoles. During the alkylation reaction of asymmetric benzotriazoles, three isomers with different substitution positions are obtained. The use of strong electron-withdrawing functional groups at C-X position results in significant difference in chemical shifts of the C-8 and C-9 in the NMR spectra. By using column chromatography and structural spectroscopy for identification, we successfully separated the three isomers obtained from the alkylation of asymmetric benzotriazoles and conducted spectral analysis of each isomer, establishing a useful standard procedure for the preparation of these isomers which would be beneficial for the future molecular design. | en_US |