Department of Chemical Engineering, Shaanxi Institute of Technology, Xi'an 710300, China.
Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China.
Molecules. 2022 Aug 27;27(17):5522. doi: 10.3390/molecules27175522.
Two water-soluble single-benzene-based chromophores, 2,5-di(azetidine-1-yl)-tereph- thalic acid (DAPA) and its disodium carboxylate (DAP-Na), were conveniently obtained. Both chromophores preserved moderate quantum yields in a wide range of polar and protonic solvents. Spectroscopic studies demonstrated that DAPA exhibited red luminescence as well as large Stokes shift (>200 nm) in aqueous solutions. Femtosecond transient absorption spectra illustrated quadrupolar DAPA usually involved the formation of an intramolecular charge transfer state. Its Frank−Condon state could be rapidly relaxed to a slight symmetry-breaking state upon light excitation following the solvent relaxation, then the slight charge separation may occur and the charge localization became partially asymmetrical in polar environments. Density functional theory (DFT) calculation results were supported well with the experimental measurements. Unique pH-dependent fluorescent properties endows the two chromophores with rapid, highly selective, and sensitive responses to the amino acids in aqueous media. In detail, DAPA served as a fluorescence turn-on probe with a detection limit (DL) of 0.50 μM for Arg and with that of 0.41 μM for Lys. In contrast, DAP-Na featured bright green luminescence and showed fluorescence turn-off responses to Asp and Glu with the DLs of 0.12 μM and 0.16 μM, respectively. Meanwhile, these two simple-structure probes exhibited strong anti-interference ability towards other natural amino acids and realized visual identification of specific analytes. The present work helps to understand the photophysic−structure relationship of these kinds of compounds and render their fluorescent detection applications.
两种水溶性单苯基发色团，2,5-二（氮杂环丁烷-1-基）对苯二甲酸（DAPA）及其二钠盐（DAP-Na），方便地获得。这两种发色团在很宽的极性和质子溶剂范围内保持中等量子产率。光谱研究表明，DAPA 在水溶液中表现出红色发光以及大斯托克斯位移（>200nm）。飞秒瞬态吸收光谱表明，偶极子 DAPA 通常涉及形成分子内电荷转移态。其弗兰克-康登态可以在溶剂弛豫后迅速松弛到轻微对称破缺态，然后可能发生轻微的电荷分离，并且在极性环境中电荷定位变得部分不对称。密度泛函理论（DFT）计算结果与实验测量结果很好地吻合。独特的 pH 依赖性荧光性质赋予这两种发色团在水相介质中对氨基酸的快速、高选择性和灵敏响应。具体而言，DAPA 作为荧光开启探针，对 Arg 的检测限（DL）为 0.50μM，对 Lys 的检测限为 0.41μM。相比之下，DAP-Na 具有明亮的绿色发光，并对 Asp 和 Glu 表现出荧光关闭响应，其 DL 分别为 0.12μM 和 0.16μM。同时，这两种结构简单的探针对其他天然氨基酸具有很强的抗干扰能力，并实现了特定分析物的可视化识别。本工作有助于了解这类化合物的光物理-结构关系，并为其荧光检测应用提供了依据。
