A general and practical
method for the direct C–H amination
of 2H-indazoles with a series of amines including
aliphatic primary amines, secondary amines, azoles, and sulfoximines
via organophotoredox-catalyzed oxidative coupling has been disclosed
at room temperature under ambient air conditions. Additionally, this
protocol is used for free aminated 2H-indazole synthesis.
A mechanistic study revealed that a single electron transfer (SET)
pathway might be involved in this reaction.
Allylamine-functionalized
silicon quantum dots (ASQDs) of high
photostability are synthesized by a robust inverse micelle method
to use the material as a fluorescent probe for selective recognition
of thiocyanate (a biomarker of a smoker and a nonsmoker). The synthesized
ASQDs were characterized by absorption, emission, and Fourier transform
infrared spectroscopy. Surface morphology is studied by transmission
electron microscopy and dynamic light scattering. The synthesized
material exhibits desirable fluorescence behavior with a high quantum
yield. A selective and accurate (up to 10–10 M)
method of sensing of thiocyanate anion is developed based on fluorescence
amplification and quenching of ASQDs. The sensing mechanism is investigated
and interpreted with a crystal clear mechanistic approach through
the modified Stern–Volmer plot. The developed material and
the method is applied to recognize the anion in the human blood sample
for identification of the degree of smoking. The material deserves
high potentiality in the field of bio-medical science.
A convenient and straightforward regioselective synthesis of pi‐conjugated pyrazolo[1, 5‐a]pyrimidines has been achieved via Brønsted acidic ionic liquid catalyzed tandem cyclization between 3‐aminopyrazole and chalcone derivatives in high yields. Task specific ionic liquid [1‐methyl‐3‐(4‐sulfobutyl)imidazolium‐4‐methylbenzenesulfonate] is found to be an effective catalyst for the cyclization, and the presence of both C2‐H of imidazolium moiety and acidic proton drastically enhance the catalytic activity. Substituted aminopyrazoles reacted with a wide range of functionalized α,β‐unsaturated ketones to variety of pyrazolo[1, 5‐a]pyrimidine derivatives. The present protocol offers a broad substrates scope, use of non‐hazardous reagent, metal‐free environmentally benign conditions and catalyst recyclability. Comparative photophysical studies have shown high quantum yields for certain derivatives.
Sulfonated polyaniline (SPANI) has emerged as a promising polymer in the past few decades due to its solubility in water and relatively moderate conductivity. However, to date, literature data on the optical characterization of SPANI are very limited and preliminary in nature. In the present work, SPANI is synthesized by direct sulfonation of emeraldine salt form of polyaniline with chlorosulfonic acid in an inert solvent. Detail photophysical properties of SPANI are investigated in aqueous medium by using steady state (concentration, temperature, pH, and excitation wavelength dependence) and time-resolved spectroscopic techniques. The steady state fluorescence emission measurements are carried out carefully to avoid inner filter effect (especially secondary inner filter effect or reabsorption effect) as well as scattering. Two ground state conformations of SPANI are suggested to exist in aqueous medium. Excitation wavelength dependence of the fluorescence emission spectra is attributed to red-edge effect. All these observations are nicely corroborated by the fluorescence lifetime data of SPANI obtained from time-resolved measurements. All these new findings are extremely important in view of the potential applications of SPANI in polymer optoelectronics.
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