Journal
JOURNAL OF ORGANIC CHEMISTRY
Volume 86, Issue 21, Pages 14663-14671Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.joc.1c01488
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Funding
- DST (J.C. Bose Fellowship)
- IACS
- IISc
- BITS-Pilani (Hyderabad campus)
- Ministry of Education, Youth and Sports of the Czech Republic [LTAIN19101]
- IndiaCzech Bilateral Scientific and Technological Cooperation
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The newly designed dye shows a dark yellow color in solution, but emits a blue fluorescence when nerve agents are added. The interaction between the nerve agents and the dye involves nucleophilic attack and hydrolysis, leading to altered electronic behavior and the release of a less-toxic organophosphate compound.
A Y-shaped push-pull dye (1) with N,N-dimethylanilino donors and a benzonitrile acceptor connected via an imidazole-based Jr-conjugated spacer was designed. It showed a dark yellow color in solution due to facile intramolecular charge-transfer interaction, but no fluorescence was detected, presumably due to the photo-induced electron transfer effect of the imidazole moiety. However, addition of nerve agents such as diethyl chlorophosphate (DCP, sarin mimic) and diethyl cyanophosphate (DCNP, Tabun mimic) resulted in a blue-colored fluorescence with fading of the native dark yellow color. Mechanistic studies indicated nucleophilic attack of imidazole at the phosphorus of DCP or DCNP, leading to the formation of a phosphorylated intermediate, which undergoes time-dependent hydrolysis (similar to 24 h) in aqueous medium. This process recovers the free probe (enzyme-like behavior) and releases a less-toxic organophosphate compound as the byproduct. The phosphorylated derivative of 1, formed during such interaction, shows a different electronic behavior, which reduces the extent of charge-transfer interaction as well as nonradiative decay and supports emissive properties. Considering the high sensitivity of 1 towards DCP and DCNP with LOD 35 and 42 ppb, we prepared easy test strips for on-site vapor-phase detection of nerve agents.
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