Naorem Jemes Meitei

Copper rapidly catalyzes nitrite to NO conversion, whereas iron stores NO as stable nitrosyl complexes. Graphical image was created with Google Gemini.

β-Diketiminato Cu( ii )–nitrito complexes react with thiols ( ^t BuBzSH, BzSH, l -cysteine) to release NO and form a free ligand, disulfide, and an insoluble polymeric Cu( i )–thiolate (YP _R ).

Congo red is toxic to humans and the environment and persists in the environment for long periods. Therefore, developing a rapid detection method for Congo red is crucial. In this study, iron oxide quantum dots (IOQDs) were synthesized and employed for dual-mode detection (colorimetric and smartphone-based) of Congo red in real samples. Upon mixing with Congo red, the IOQDs induce a color change in the solution due to the strong intermolecular interactions between Congo red and the IOQDs, making them practical as colorimetric sensors. To further increase the on-site detection capabilities of IOQDs, images of the sensor platform were captured using a smartphone, and the color data were analyzed with a dedicated APP. As a colorimetric sensor, the ultraviolet-visible (UV-vis) absorbance response exhibited good linearity for Congo red concentrations between 2 and 50 μM, with a detection limit of 0.89 μM. The smartphone-based sensor also provided highly quantitative results, showing a linear relationship between Congo red concentrations and the blue-to-red (B/R) channel ratio, with a detection limit of 0.58 μM. Moreover, this dual-mode method demonstrated better selectivity for Congo red than other colorimetric sensors, even in the presence of other red dyes. The proposed method is convenient, fast, low-cost, and suitable for real-sample applications.

An investigation on the reactivity of O-2 bindingtounsymmetrical beta-diketiminato copper-(I) complexes by spectroscopicand titration analysis was performed. The length of chelating pyridylarms (pyridylmethyl arm vs pyridylethyl arm) leads to the formationof mono- or di-nuclear copper-dioxygen species at -80 degrees C.The pyridylmethyl arm adduct (L-1 CuO2) forms mononuclear copper-oxygen species and shows ligand degradation,resulting in the formation of (2E,3Z)-N-(2,6-diisopropylphenyl)-4-(((E)-pyridin-2-ylmethylene)-amino)-pent-3-en-2-imine, which slowly convertsto its cyclization isomer 1-(2,6-diisopropylphenyl)-4,6-dimethyl-2-(pyridin-2-yl)-1,2-dihydropyrimidineafter addition of NH4OH at room temperature. On the otherhand, the pyridylethyl arm adduct [(L-2 Cu)(2)(mu-O)(2)] forms dinuclear species at -80 degrees C and does not show any ligand degradation product. Instead,free ligand formation was observed after the addition of NH4OH. These experimental observations and product analysis resultsindicate that the chelating length of pyridyl arms governs the Cu/O-2 binding ratio and the ligand degradation behavior.