On the basis of the experimentally reported near-infrared (NIR) fluorescent probe for peroxynitrite anions (ONOO) DDAO-PN (DDAO = 1,3-dichloro-7-oxygen-9,9-dimethyl-2(9H)-acridinone, PN = 4- methylene benzeneboronic acid pinacol ester, DDAO-PN connecting 7-oxygen of DDAO with 4- methylene of PN), six DDAO derivatives DDAO-Px (x = 1–6) were designed. The fluorescence response mechanism and characteristics of the DDAO-PN probe to ONOO were explored and the molecular structures, molecular orbital, and electron transfer during excitation and emission in DDAO-PN and DDAO-Px (x = 1–6) were comparatively analyzed in detail through the density functional theory (DFT) and time-dependent DFT calculations. The significant intramolecular charge transfer (ICT) effect in DDAO-PN were found to be released when PN (as the recognition domain of ONOO in the recognition process) was removed, rendering DDAO-PN being an effective “off-on” NIR ONOO fluorescent probe. The introduction of different electron-donating/accepting substituents in DDAO-Px significantly changed the electronic structures and thus the fluorescent properties, which finally modified the probe efficiency. This work clarifies the structure-property relationship in DDAO-Px type NIR probes and thus provides theoretical guidance for designing new NIR fluorescent probe.

中文翻译：

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过氧亚硝酸盐近红外荧光探针新型荧光团的理论设计

基于实验报道的过氧亚硝酸根阴离子 (ONOO) DDAO-PN 的近红外 (NIR) 荧光探针 (DDAO = 1,3-二氯-7-氧-9,9-二甲基-2(9H)-吖啶酮， PN = 4-亚甲基苯硼酸频哪醇酯，DDAO-PN（连接DDAO的7-氧与PN的4-亚甲基），设计了六种DDAO衍生物DDAO-Px（x = 1-6）。探讨了DDAO-PN探针对ONOO的荧光响应机制和特征，并对DDAO-PN和DDAO-Px（x = 1-6）在激发和发射过程中的分子结构、分子轨道和电子转移进行了比较分析。通过密度泛函理论 (DFT) 和瞬态 DFT 计算详细了解。当PN（识别过程中ONOO的识别域）被去除时，DDAO-PN中显着的分子内电荷转移（ICT）效应被释放，使得DDAO-PN成为有效的“off-on”NIR ONOO荧光剂探测。在DDAO-Px中引入不同的给电子/受电子取代基显着改变了电子结构，从而改变了荧光特性，最终改变了探针效率。该工作阐明了DDAO-Px型近红外探针的构效关系，为设计新型近红外荧光探针提供了理论指导。