Silver-modified polyniobotungstate for the visible light-induced simultaneous cleavage of C–C and C–N bonds

Abstract

A silver-modified polyniobotungstate based on Nb/W mixed-addendum polyoxometalate with the formula of Ag9[P2W15Nb3O62]•21H2O (Ag-Nb/W) has been synthesized and characterized by various analytical and spectral techniques. Ag-Nb/W was proved to be an efficient photocatalyst for the oxidative ring openings of 2-phenylimidazo[1,2-a]pyridine via simultaneous cleavage of C-C and C-N bonds. Under visible light (430-440 nm), using oxygen as an oxidant at room temperature, Ag-Nb/W can catalyze the rapid transformation of various 2-phenylimidazo[1,2a]pyridine derivatives to produce the corresponding oxidative ringopening product N-(pyridin-2-yl) amides in good isolated yields ranging from 65% to 78%. As a heterogeneous photocatalyst, Ag-Nb/W showed excellent sustainability and recyclability in the recycling experiments. IR spectroscopy and XRD analysis indicated that Ag-Nb/W could retain its integrity after catalysis. A possible mechanism involving singlet oxygen was proposed for the catalytic reaction.

New High-Performance Fluorescent Dye Scaffolds: Applications for Bioimaging and Biosensing

“…The dibenzylideneacetone 6 was prepared in 95% yield through aldol condensation of 4 with 1,4-cyclohexanedione monoethylene acetal (5). Compound 8 was obtained by reacting 6 with lithiated diphenyl ether (7) followed by an acid-promoted six-step cascade, in an overall 67 % yield. Or compound 6 could be treated with MeSO3H to give pentacenedione 9.…”

“…Or compound 6 could be treated with MeSO3H to give pentacenedione 9. Subsequent addition of mono-lithiated diphenyl ether (7) to 9 occurred regioselectively to generate 10, acid-catalyzed cyclization of which also leads to 8. Finally, reactions between 8 and various Grignard reagents (11a-f) could afford ECXa-f in a good yield, ranging from 61-72 %.…”

“…Their photophysical mechanisms and bioanalytical applications are multidisciplinary and cutting-edge research topics. 7,8 We have been working on high-performance fluorescent dyes and fluorescent probes for years. To address the problems of penetration depth and background interference in fluorescent imaging in vivo, we have done systematic work on chemical and biological sensing.…”

{Ti12} Cluster-Added Poly(polyoxometalate) Containing Mixed Trivacant Keggin and Dawson Fragments

“…Polyoxometalates (POMs), an important class of nanosized metal–oxygen clusters with tremendous structural diversities and rich electronic properties, have putative and realized applications in various fields such as catalysis, medicine, and magnetochemistry. − Over the past few decades, the continuous and rapid development of new POMs has largely arisen as a result of the diversity and suitability of the preformed lacunary POM fragments which can provide abundant active sites for capturing additional metal ions (transition metal (TM), rare earth (RE)) to derive TM/RE added POMs and bring about unpredictable functionalities. , Among them, lacunary Keggin and Dawson POM building blocks are widely used in the construction of novel POMs and play an important role in enriching structural chemistry. To date, TM-added POMs (TMAPs) are well established and a number of remarkable structures have been made. − However, most of these reported TMAPs are built by a single type of lacunary POM fragments.…”

An Important Photocatalysis Oxidation: Selective Oxidation of Aniline to Azobenzene over a {P4Mo6}-based Crystalline Catalyst Under Visible-light Irradiation at Room Temperature

“…Light-driven chemical conversion is perceived as a promising renewable energy utilization method to convert natural light energy into high-value-added chemical energy via electron transfer. − Especially, the research on light-driven organic synthesis is in the early exploratory stage so far. − The photocatalytic oxidation reaction of aniline and its derivatives to aromatic azo-compounds is significant, because aromatic azo-compounds treated as high-added-value chemical products have a wide range of applications in organic dyes, biopharmaceuticals, nonlinear optical materials, and other fields. , In the past two decades, metal matrix nanocomposites have been successfully applied to the catalytic oxidation of aniline to azobenzene (AB; − Scheme a). Nevertheless, some factors still restrict the practical application of these catalysts: (i) inconclusive catalytic active sites, , (ii) excessive addition of catalysts or oxidants, , (iii) harsh reaction temperature or pressure, , and so on.…”