Articles written in Journal of Chemical Sciences

    • A water soluble heteropolyoxotungstate as a selective, efficient and environment friendly oxidation catalyst

      Prasenjit Maity Double Mukesh Sumit Bhaduri Goutam Kumar Lahiri

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      A series of water soluble Keggin type heteropolyoxotungstates have been tested as oxidation catalysts in aqueous-biphasic media with dilute H2O2 (30%) as the oxygen atom donor, without using any phase transfer agent. The Zn substituted polyoxoanion {(NH4)7Zn0.5[𝛼-ZnO4W11O30ZnO5(OH2)]$.n$H2O} has been found to be the most efficient catalyst, which oxidizes a wide range of organic functionalities with good turnovers and high selectivities. The functionalities that undergo oxidations are: organic sulfides, pyridines, anilines, benzyl alcohols and benzyl halides. The oxidations of sulfides to sulfoxides and/or sulfones have been studied in detail, and a simple kinetic model consisting of two consecutive reactions, is shown to give good fit with the experimental data. In the catalytic system described here product isolation is easy, and the aqueous catalyst solution can be re-used several times with little loss in its efficiency.

    • An organometallic ruthenium nanocluster with conjugated aromatic ligand skeleton for explosive sensing


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      9-Ethynylphenanthrene (EPT) bound to highly monodispersed Ruthenium (Ru) nanocluster (Ru:EPT) with mean diameter of 1.5 ± 0.2 nm and mol wt. of ~8600 Da was synthesized via a facile and high yield biphasic ligand exchange protocol using similar sized ethylene glycol (EG)-stabilized Ru clusters (Ru:EG) as precursor. The synthesized organometallic nanocluster was meticulously analyzed to understand its size distribution, oxidation state, crystallinity, optical and luminescence behavior and metal–ligand interfacial structure. Contrary to the extensive quenching of ligand emission by metalcore as usually observed, the ruthenium core here acts as a conductor, which conjugates surface ligands with strong emission property courtesy to an unusual vinylidene-binding motif. Thus, the synthesized nanocluster shows good luminescence property (φ= ~7%) originated from the ligand skeleton and the spherical metal core restricts lateral overlap of phenanthrene moiety to cause any excimer emission. This nanocluster showed high sensitivity for solution phase detection of nitroaromatic explosives through luminescence quenching method (KSVup to 498×10.4M -1) andmimic the mechanism like conjugated organic polymer. We propose that dynamic χ−χ interaction between Ru bound phenanthrene moiety and nitroaromatic compounds followed by photoinduced electron transfer (PET), as well as Förster Resonance Energy Transfer (FRET), are the possible mechanisms behind this luminescence quenching.

    • Selective sensing of thiols by aryl iodide stabilized fluorescent gold cluster through turn-off excimer emission caused by ligand displacement


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      Here we report fluorescence quenching based detection of selected ‘‘Thiol’’ molecules byemploying a luminescent gold cluster through ligand displacement strategy. First, an aryl iodide (2-Iodonaphthalene,NP) and polyvinylpyrrolidone (PVP) mixed ligand stabilized gold cluster was synthesized with astrong fluorescence signal originated from excimer of 2-Iodonaphthalene ligands grafted on gold nano surface.Among different small molecule-based ligands, thiol (R-SH) forms a strong bond with gold nanoparticles.Anticipating this property, we have found that displacement of 2-Iodonaphthalene ligand from goldnanoparticle surface by thiols results in the sensitive detection of thiols through the quenching of emission ofgold cluster. The selectivity for detection of different tested analytes follows the order: GSH>Cys>hCywhereas, other non-thiol based amino acids and common salts are innocent towards fluorescence response.Easy synthesis of the fluorescent gold cluster, selective sensing of small thiol molecules, high Stern-Volmerconstant (KSV=3.3×106 M-1) and ultralow detection limit (LOD of 35 nM) are notable features of the presentreport.

      A fluorescence turn-off chemosensor has been developed for sensing selected ‘thiol’ molecules by employing 2-Iodonaphthalene and polyvinylpyrrolidone (PVP) mixed ligand stabilized luminescent gold cluster through ligand displacement strategy.

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