• Anunay Samanta

      Articles written in Journal of Chemical Sciences

    • Optical absorption and fluorescence studies on imidazolium ionic liquids comprising thebis(trifluoromethanesulphonyl)imide anion

      Aniruddha Paul Anunay Samanta

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      Optical absorption and fluorescence behaviour of two rigorously purified imidazolium ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide are studied in the neat condition and in solution. Non-negligible absorption in the UV region with a long tail extending into the visible region is the main feature of the absorption. Excitation wavelength-dependent two-component fluorescence characterizes the emission behaviour of these liquids. That ion association gives rise to the long absorption tail and shifting fluorescence maximum, which appears to be common to most of the imidazolium ionic liquids, is evident from the effect of the conventional solvents

    • Ratiometric fluorescence signalling of fluoride ions by an amidophthalimide derivative

      Moloy Sarkar Raghavendra Yellampalli Bhaswati Bhattacharya Ravi Kumar Kanaparthi Anunay Samanta

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      Fluorescence behaviour of 4-benzoylamido-N-methylphthalimide (1), designed and developed for selective detection of fluoride ions, is reported. 1 displays $F^-$-induced colour change that allows its detection with the naked eye. The $F^-$ specificity of the sensor system is evident from the fact that unlike $F^-$, other halides do not affect the absorption characteristics of 1. Apart from the colorimetric response, the fluorescence output of 1 is also modulated by $F^-$ in a manner that permits ratiometric fluorescence signalling of $F^-$ as well. It is found that the system can detect $F^-$ in the concentration range of $10^-$ 60 𝜇M. The results of the experiments and theoretical calculations unambiguously suggest that the changes of the electronic absorption and fluorescence behaviour of 1, which have been exploited for signalling purpose, are due to $F^-$-induced deprotonation of the 4-amido moiety of the sensor system.

    • Excited state dynamics of 9,9'-bianthryl in room temperature ionic liquids as revealed by picosecond time-resolved fluorescence study

      Dinesh Chandra Khara Aniruddha Paul Kotni Santhosh Anunay Samanta

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      Picosecond time-resolved fluorescence measurements have been carried out on 9,9'-bianthryl in three imidazolium ionic liquids to probe the excited state dynamics. In the early time-scale, the fluorescence spectra of bianthryl have been found to consist of emission from both locally excited (LE) and charge transfer (CT) states. The LE → CT relaxation time, as estimated from the decay of the fluorescence intensity of the LE emission, is found to vary between 230 and 390 ps, while the average solvent relaxation time, as estimated from the analysis of time-dependent fluorescence Stokes shift, is found to vary between 620 ps and 1840 ps, depending on the viscosity of the ionic liquids. The results confirm that while in conventional less viscous solvents the CT formation kinetics of bianthryl occurs simultaneously with the solvation dynamics, in ionic liquids the two processes mostly occur in different time scales.

    • Laser flash photolysis study on 9-phenylxanthenium tetrafluoroborate: Identification of new features due to the triplet state

      Sanghamitra Banerjee Anunay Samanta

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      Laser flash photolysis study on highly fluorescent and stable salt of 9-phenylxanthenium cation in neutral condition has been carried out for the first time. A new transient absorption band of this extensively studied system that perhaps remained buried under the fluorescence envelope and hitherto undetected has been identified and attributed to the triplet state of the system. This oxygen-insensitive triplet-triplet absorption band in the 480-600 nm range is expected to trigger new studies exploring the reactivity of the triplet state of this system, which has so far received very little attention.

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