Chettri Bimal, Pal Animesh, Jha Satadru, Dey Nilanjan
Department of Chemistry, Sikkim Manipal Institute of Technology, Sikkim Manipal University, Majitar, Sikkim 737136, India.
Department of Chemistry, Birla Institute of Technology and Sciences-Pilani Hyderabad Campus, Shameerpet, Hyderabad 500078, Telangana, India.
Dalton Trans. 2024 Apr 2;53(14):6343-6351. doi: 10.1039/d3dt04172g.
Anthraimidazoledione-based optical sensors have been designed by varying the position of the nitro functional group. All three positional isomers showed highly colored, photostable optical signals owing to intramolecular charge transfer interactions. Despite having the same anion-binding site (imidazole unit), the selectivity and sensitivity of the compounds depend on the positioning of the nitro group. The selectivity was fairly good for the isomer, followed by the and isomers, respectively. In contrast, the sensitivity towards anions followed a completely opposite trend, with the isomer being the most sensitive one towards anions. Interestingly, the color changing response along the turn-on fluorescence signal was observed only with CN- ions in a semi-aqueous environment. Though the introduction of water as a co-solvent could improve the selectivity, the sensitivity was found to be slightly less than that observed in pure organic medium. Mechanistic studies indicated hydrogen bonding interactions between the imidazole -NH proton and cyanide, which further facilitated the extent of intramolecular charge transfer.
通过改变硝基官能团的位置设计了基于蒽咪唑二酮的光学传感器。由于分子内电荷转移相互作用，所有三种位置异构体均显示出颜色深且光稳定的光学信号。尽管具有相同的阴离子结合位点（咪唑单元），但这些化合物的选择性和灵敏度取决于硝基的位置。对于 异构体，选择性相当好，其次分别是 异构体和 异构体。相反，对阴离子的灵敏度呈现完全相反的趋势， 异构体对阴离子最为敏感。有趣的是，仅在半水相中与 CN-离子一起观察到了沿开启荧光信号的颜色变化响应。虽然引入水作为共溶剂可以提高选择性，但发现灵敏度略低于在纯有机介质中观察到的灵敏度。机理研究表明咪唑 -NH 质子与氰化物之间存在氢键相互作用，这进一步促进了分子内电荷转移的程度。
