• Ranjan Das

      Articles written in Journal of Chemical Sciences

    • Heisenberg spin exchange and chemical electron exchange in napthalene negative ion—An electron spin-lattice relaxation study

      Ranjan Das Balu Venkataraman

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      Electron spin-lattice relaxation times (T1e) as determined by saturation recovery technique and linewidths have been investigated as a function of the concentration of napthalene anion and the unreduced napthalene in dimethoxyethane from conditions of slow exchange to fast exchange. It was observed that Heisenberg spin exchange was more effective in determiningT1e and linewidth than chemical exchange at comparable concentrations. Contrary to earlier findings,T1e was found to depend on the radical concentration even at the fast exchange regime.

    • Time-domain electron-spin-resonance studies on hydrogen atom transfer to photoexcited quinones

      Ranjan Das P K Radha Balu Venkataraman

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      Time-domain electron-spin-resonance studies onp-benzoquinone using ethanol and isopropanol as solvents show emissively polarized ESR spectra of semiquinone and hydroxyalkyl radicals within 0·5 μs after the laser pulse at 248 nm. The hydrogen abstraction from the alcohols by the triplet excited quinone is concluded to be the primary photochemical step.

    • Absorption and emission spectra of 4-methyl-2,6-diformyl phenol in protic solvents: Interaction with amine bases

      Reba Roy Sivaprasad Mitra Ranjan Das Samaresh Mukherjee

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      The interaction of 4-methyl-2,6-diformyl phenol (MFOH) with tributylamine and trioctylamine has been studied quantitatively in protic solvents by means of absorption and fluorescence spectroscopy with special emphasis on proton transfer. It is observed that (a) the intensity of the absorption band in the 430–450 nm region due to the phenolate anion (MFO) increases with increasing amine concentration; (b) the change in the intensity of the absorption band in the 350 nm region due to intramolecularly hydrogen bonded MFOH follows inversely the change in intensity of the absorption band due to the anion at 430–450 nm region (c) the intensity of the fluorescence band around 480–520 nm region due to the MFO anion increases with increase in the added base concentration. The results are interpreted in terms of proton transfer from MFOH to an amine base to yield an anion MFO both in the ground and excited electronic states. Equilibrium data for the proton transfer reaction between MFOH and amine bases (B) in ethanol, butanol and water as solvents have been obtained and discussed.

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