A unique turn-on fluorescent device based on a ferrocene–aminonaphtholate derivative specific for Hg²⁺ cation was developed. Upon binding with Hg²⁺ ion, the probe shows a dramatic fluorescence enhancement (the fluorescence quantum yield increases 58-fold) along with a large red shift of 68 nm in the emission spectrum. The fluorescence enhancement with a red shift may be ascribed to the combinational effect of C═N isomerization and an extended intramolecular charge transfer (ICT) mechanism. The response was instantaneous with a detection limit of 2.7 × 10^–9 M. Upon Hg²⁺ recognition, the ferrocene/ferrocenium redox peak was anodically shifted by ΔE_1/2 = 72 mV along with a “naked eye” color change from faint yellow to pale orange for this metal cation. Further, upon protonation of the imine nitrogen, the present probe displays a high fluorescence output due to suppression of the C═N isomerization process. Upon deprotonation using strong base, the fluorescence steadily decreases, which indicates that H⁺ and OH^– can be used to regulate the off–on–off fluorescence switching of the present probe. Density functional theory studies revealed that the addition of acid leads to protonation of the imine N (according to natural bond orbital analysis), and the resulting iminium proton forms a strong H-bond (2.307 Å) with one of the triazole N atoms to form a five-membered ring, which makes the molecule rigid; hence, enhancement of the ICT process takes place, thereby leading to a fluorescence enhancement with a red shift. The unprecedented combination of H⁺, OH^–, and Hg²⁺ ions has been used to generate a molecular system exhibiting the INHIBIT–OR combinational logic operation.

中文翻译：

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ICT异构化诱导的汞离子发射位移大的开启荧光探针：在组合分子逻辑中的应用

基于Hg ²⁺阳离子特有的二茂铁-氨基萘甲酸衍生物，开发了一种独特的开启荧光装置。与Hg ²⁺离子结合后，探针在发射光谱中显示出显着的荧光增强（荧光量子产率增加58倍）以及68 nm的大红移。具有红移的荧光增强可能归因于C═N异构化和扩展的分子内电荷转移（ICT）机制的组合作用。的反应是瞬时的与2.7×10的检测极限^-9 M.当汞²⁺识别，二茂铁/二茂铁的氧化还原峰是由Δ阳极移位ë _1/2= 72 mV，并且该金属阳离子的颜色从微弱的黄色变为浅橙色，“肉眼可见”。此外，在亚胺氮的质子化作用下，由于抑制了C isN异构化过程，本发明的探针显示出高荧光输出。在使用时的强碱去质子化，所述荧光稳定地降低，这表明使得h ⁺和OH ^-可用于调节本探针的开-关-关荧光切换。密度泛函理论研究表明，添加酸会导致亚胺N的质子化（根据自然键轨道分析），所得的亚胺质子与三唑N原子之一形成强H键（2.307Å）五元环，使分子刚性；因此，ICT过程得到了增强，从而导致荧光增强并出现红移。H的前所未有组合⁺，OH ^- ，和Hg ²⁺离子已被用来产生一个分子系统表现出INHIBIT-OR组合逻辑的操作。