• M M Taqui Khan

      Articles written in Journal of Chemical Sciences

    • Thermodynamic fitness of an RuIII(EDTA)/RuV = O(EDTA) couple in the oxygen atom transfer reactions

      M M Taqui Khan A Prakash Rao S A Samad Debabrata Chatterjee S D Bhatt R R Merchant

      More Details Abstract Fulltext PDF

      The complex [RuIII(EDTA-H)(H2O)]1 (EDTA-H = protonated ethylenediaminetetraacetic acid) catalyzes the epoxidation of cyclohexene and the oxidation of PPh3 to OPPh3 with molecular oxygen or NaOC1 as the oxidant. In both the cases, the active catalytic species is the [Ruv = O(EDTA)] ion2 characterized by elemental analyses, UV-vis, infrared spectra and cyclic voltammograms.

      When oxygen is used as an oxidant in the reaction, oxidation of the substrates proceeds through aμ-peroxo-Ru(IV) intermediate [RusiIV(EDTA)(S)]2O22−3 (S = olefin, PPh3) which undergoes a fast homolytic cleavage of the O-O bond to form [Ruv = O(EDTA)(S)]4 and a rate determining transfer of O atom to S to form SO and1. The cleavage of the O-O bond in 3 and O-atom transfer to S proceed in a concerted step.

      With NaOCl as an oxidant (excess), oxidation of1 to2 proceeds through a unimolecular decomposition of the [RuIII(EDTA)(OCl)]2− intermediate. The transfer of the O-atom from2 to S proceeds by an associative(Ia) pathway involving a concerted cleavage of the Ru=O bond and formation of an SO bond. The free energy (ΔG) values for various steps are computed and the thermodynamic fitness of2 as an oxidant discussed.

    • Photofixation of carbon dioxide in semiconductor particulate and microbial systems

      M M Taqui Khan Debabrata Chatterjee Jayshree Bhatt

      More Details Abstract Fulltext PDF

      Photocatalytic reduction of CO2 to HCOOH and HCHO was carried out in a Pt/CdS/RuO2 semiconductor particulate system using [RuIII(EDTA-H)H2O] complex as catalyst. Upon illumination at 505 nm (band gap energy of CdS), the system produced HCOOH and HCHO at rates equal to 3.05 × l0−2 Mh−1 and 2.0 × 10−2 M h−1, respectively. Trace amounts of CH2OH, CH4 and CO were also detected in the reaction vessel. Photobiological conversion of CO2 to formic acid was achieved by usingHalobacterium halobium MMT22 in aqueous solution at a rate equal to 0.45 M h−1. A one-and-half-fold increase in the rate of formation of formic acid was observed when the photobiological reduction of CO2 was performed in the presence of L-ascorbic acid as electron-donating agent and [RuIII(bipy)3]2+ as photosensitizer.

    • Oxidation of olefins catalysed by (HEDTA) Ruv = O

      M M Taqui Khan Debabrata Chatterjee S Sanal Kumar Z Shirin M A Moiz S D Bhatt

      More Details Abstract Fulltext PDF

      The complex K[RuIII(HEDTA)Cl].H2O1 and [(HEDTA) Ruv = O]2 were prepared and characterised by elemental analysis, IR, UV-Vis spectroscopy, conductivity, magnetic susceptibility and electrochemical studies (HEDTA-hydroxyethyl-ethylenediaminetriacetate anion). The kinetics of oxygen atom transfer of [RuIII(HEDTA) (H2O)]1a to [(HEDTA) Ruv = O]2 with iodosoylbenzene was studied spectrophotometrically by using stopped-flow technique. The oxygen atom transfer from complex2 to cyclohexene, cyclooctene, styrene,cis andtrans-stilbene was studied by the disappearance of the characteristic oxo peak (λmax = 391 nm) at constant pH (3.0) and ionic strength (μ= 0.1 M NaClO4) and also product analysis by gas chromatography (GC). The activation parameters for both the oxygenation of complex1 to complex2, and oxygen atom transfer from complex2 to the organic substrates studied were evaluated and suitable mechanisms proposed.

  • Journal of Chemical Sciences | News

© 2021-2022 Indian Academy of Sciences, Bengaluru.