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Imidazo[1,2-a] pyridine-based two probes with different substituents containing oxime and hydroxyl functional groups were synthesised and evaluated for detection of tabun nerve agent simulant diethylcyanophosphonate (DCNP). The nucleophile hydroxyl group present on both the probes can be rapidly phosphorylated by DCNP through a nucleophilic substitution reaction. The probes were fluorescent and on reacting with DCNP underwent fluorescence OFF, which can be visualised under a UV lamp at 365 nm wavelength. The limit of detection for probes 1 and 2 was calculated as 0.66 μM and 0.54 μM, respectively. The mechanism of detection was studied using spectroscopic techniques revealed that the hydroxyl group is involved in the reaction with DCNP. The probes were found selective for the detection of DCNP in presence of other electrophilic interfering agents. Results were obtained in aqueous media and probes can be used directly for the rapid and sensitive detection of DCNP in water without any pretreatment. [ABSTRACT FROM AUTHOR]

Herein, two fluorescent probes IM‐MN and IM‐ECA based on D‐π‐A system were synthesized, characterized, and evaluated for their photophysical properties. The probes were found to exhibit solvatochromic properties showing the range of fluorescence color in different polar solvents. The solvatochromism of the probes was further employed for DCNP detection. Both the probes showed excellent sensitivity and selectivity towards DCNP with fluorescence quenching response in the presence of DCNP, under UV lamp (365 nm). The probe IM‐ECA was found more sensitive in comparison to IM‐MN for detecting the presence of DCNP even at the nanomolar range. The SEM analysis has revealed the phenomenon of aggregation upon interaction of probe with DCNP that led to fluorescence quenching further, blue shift of the absorption band in UV spectra indicated formation of H‐ aggregates. Also, probes IM‐MN and IM‐ECA were fabricated into portable paper strips for real‐time detection that also resembles the response obtained in the solution phase. [ABSTRACT FROM AUTHOR]

Selective optical detection of highly toxic nerve agents and their mimics like diethyl cyanophosphate (DCNP) is of paramount importance for armed forces and first responders in order to decide the suitable medical countermeasures. The reported optical chemical sensors for DCNP suffered from poor selectivity due to their single point covalent interaction with analyte. To overcome this limitation, we herein, report a novel protocol utilizing a ditopic chemodosimeter which, in presence of tetrabutylammonium hydroxide (TBAOH), underwent dual interaction with reactive subunits of DCNP, viz., electrophilic phosphorus and cyanide, to induce unique changes in its fluorescence as well as colorimetric properties. Other interfering analytes could not trigger the similar optical response in the sensing probe due to the absence of electrophilic phosphorus and cyanide. A truth table was constructed to reveal that only DCNP but not other analytes could induce changes in both fluorescence as well as colorimetric properties of sensing probe. The linearity range of the proposed method was found to be 30–70 μM while chromogenic limit of detection (LOD) was calculated to be 99 nM which are comparable to the reported methods. Thus, use of indigenously available 2‐hydroxy‐1‐naphthaldehyde as sensing probe without requiring further chemical manipulation represented a significant improvement over the literature methods for DCNP sensing. [ABSTRACT FROM AUTHOR]

The highly sensitive, selective, easy-to-prepare, aqueous media based on two novel probes 2-(pyren-1-yl)imidazo[1,2- a ]pyridine (IMP-Py) and (2-(pyren-1-yl)imidazo[1,2- a ]pyridin-3-yl)methanol (IMP-Py-OH) are synthesized for the detection of toxic chemical warfare nerve agent mimic diethylcyanochlorophosphonate (DCNP). Both probes are found effective in the detection of DCNP but comparatively, IMP-Py shows better properties in terms of instantaneous response, specificity, selectivity and a low detection limit of 16.9 nM. A significant enhancement of fluorescence intensity of IMP-Py due to aggregation-induced emission enhancement (AIEE) and photoinduced electron transfer (PET) phenomenon was inhibited due to phosphorylation of the hydroxy group of IMP-Py-OH in presence of DCNP has been observed. Taking the advantages of good sensitivity and fast response, probe IMP-Py has been fabricated into a viable paper strips portable product, tested for its potential for the detection of DCNP in tap water as well as with its vapor and response is visible under a UV lamp of 365 nm wavelength. [Display omitted] • Imidazopyridine-pyrene-based fluorescent probes are developed for the detection of Tabun mimic. • Probes show Fluorescence ON response upon the addition of DCNP in an aqueous medium. • IMP-Py has high sensitivity for DCNP than IMP-Py-OH. • IMP-Py shows the AIEE mechanism in presence of DCNP in an aqueous medium. • PET-OFF along with AIEE mechanism are operated in IMP-Py-OH in presence of DCNP. [ABSTRACT FROM AUTHOR]

Abstract: Gold nanoparticles functionalized with a triarylcarbinol derivative have been used as colorimetric molecular probes for the naked-eye detection of the nerve agent simulants DCNP and DFP. The detection process is based on the compensation of charges at the surface of the nanoparticles which triggers their aggregation in solution with the resulting change in their plasmon band. [Copyright &y& Elsevier]

Abstract: The FT-IR and FT-Raman vibrational spectra of 2,4-dichloro-5-nitropyrimidine (DCNP) and 4-methyl-2-(methylthio)pyrimidine (MTP) have been recorded in the range 4000–400 and 3600–50cm−1, respectively. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry and vibrational frequencies in the ground state are calculated using density functional B3LYP method with 6-31+G(d,p) and 6-311++G(d,p) basis set combinations. With the help of specific scaling procedures, the observed vibrational wavenumbers in FT-IR and FT-Raman spectra are analyzed and assigned to different normal modes of the molecules. The predicted first hyperpolarizability reveals that the molecules are an attractive object for future studies of non-linear optical properties. And also HOMO–LUMO energy gap explains the eventual charge transfer interaction taking place within the molecules. UV–vis spectral analysis of the title compounds has been researched by theoretical calculations. The frontier orbital energies, absorption wavelengths (λ), oscillator strengths (f) and excitation energies (E) studied using TD-DFT (B3LYP) with 6-311++G(d,p) basis set are calculated in this work. [Copyright &y& Elsevier]

Abstract: 2-Amino-4-methoxy-6-methyl-pyrimidine (AMMP) and 2-amino-4,6-dimethyl-pyrimidine (ADMP) react with 2,6-dichloro-4-nitrophenol (DCNP) to form yellow proton transfer (PT) complexes in acetonitrile at absorption maxima around 420nm. These PT reactions have been applied to the simultaneous spectrophotometric determination of (AMMP) and (ADMP) in acetonitrile. Factors controlling the PT process were studied and optimized. Job''s method of continuous variations was applied to identify the composition of the formed complexes. The PT complex formation constants (K PT) and the molar extinction coefficients (ε) were estimated using Benesi–Hildebrand equation. Moreover, the solid PT complexes were isolated and characterized using elemental analysis and infrared measurements. [Copyright &y& Elsevier]

Chemical warfare agents (CWAs) are the most feared and unpredictable terrorist weapon that threaten global security. For the issue of human security, it is highly demanded to establish rapid and reliable methods for the detection of CWAs. In this work, a hemicyanine-based colorimetric and off-on fluorescent dual-modal probe for the detection of a nerve agent mimic diethyl cyanophosphonate (DCNP) has been developed. The probe exhibits fast response (<3 min), high selectivity, and excellent sensitivity with a low limit of detection (4.5 nM). More importantly, test strips loaded with the probe can sense DCNP vapor in low concentration and distinguish DCNP vapor from other nerve agent mimics by both naked eyes and fluorescence. Image 1 • An ultrasensitive OFF-ON fluorescent probe for DCNP was developed. • The probe exhibited a fast fluorescence response to DCNP within 180 s with a low detection limit of 4.5 nM. • The probe displayed colorimetric and fluorescent dual-responses for DCNP. • The filter paper with the probe can sensitively and selectively detect DCNP vapor. [ABSTRACT FROM AUTHOR]