Department of Chemistry

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Author: search.filters.author.Chakraborty, AmritaSubject: search.filters.subject.Halogen bond

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    Investigation of [CH2I2–R2S] complexes (R = –H, –CH3) in cryomatrix: Propensity towards C–I⋯S halogen bond and C–H⋯S hydrogen bond interaction
    (Elsevier, 2025-12) Chakraborty, Amrita; Chakraborty, Shamik
    The volatile organic iodine compound (Image 1) and volatile bivalent sulphur compounds, such as, Image 2, Image 3, are trace gases present with high concentration in the coastal area and are important constituents for the chemical processes in the area of atmospheric science. The Image 4 is one of the iodine precursors in the atmosphere, and Image 5 and Image 6 play a major role in the sulphur cycle. Depending on the nature of the Lewis bases, the type of interactions between the constituents may alter, which would influence the final product in a chemical reaction, nucleation process, and radiative forcing. The key objective of this work is to understand the plausible interaction between Image 7 and sulphur-containing Lewis bases (Image 8, Image 9), and to identify the propensity towards the formation of hydrogen bond and halogen bond interaction at the molecular level using matrix-isolation FTIR spectroscopy. Electronic structure calculations have been performed in the ground electronic state to predict the possible structures and stability of the clusters. The thermodynamic properties of the dimers have been evaluated along with their higher-order clusters to understand the possibility of forming such complexes in the atmosphere.
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    Investigation of [CHCl3-CH3OH] complex using matrix-isolation IR spectroscopy and quantum chemical calculation: Evidence of hydrogen- and halogen-bonding interaction
    (Elsevier, 2022-03) Chakraborty, Amrita; Chakraborty, Shamik
    Mixture of CHCl3-CH3OH is a popular non-aqueous solvent mixture that exhibits strong synergistic solvation. The specific interaction between the CHCl3 and CH3OH is investigated using 1:1 complex in N2 matrix along with electronic structure calculation. Three different type of interactions are possible between CHCl3 and CH3OH at the molecular level: C-HO hydrogen bond, O-HCl hydrogen bond, and C-ClO halogen bond. One C-HO hydrogen bond minimum, two O-HCl hydrogen bond minima, and one C-ClO halogen bond minimum are obtained on the [CHCl3-CH3OH] dimer potential energy surface. Formation of C-HO hydrogen bonded and C-ClO halogen bonded 1:1 complex of [CHCl3-CH3OH] in N2 matrix is confirmed using experimental and simulated IR spectra. The outcome of the current work would help to explain the specific interactions present in CHCl3 and CH3OH binary solvent mixture and to estimate the responses of such non-aqueous solvent mixture.
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    Atmospherically relevant halogen- and hydrogen- bond complex [CCl4 single bond(H2Y)n] with Y = O and S, n 4: A computational study on Rayleigh scattering properties
    (Elsevier, 2023-11) Chakraborty, Amrita; Chakraborty, Shamik
    In troposphere, CCl4 may interact with volatile compounds that may finally contribute to the aerosol formation or atmospheric nucleation. Herein, first solvation shell of CCl4 with (H2O)n and (H2S)n is investigated. The Csingle bondClO and Csingle bondClS types of halogen bond and Osingle bondHCl and Ssingle bondHCl types of hydrogen bond have been considered. Molecular structure of the complexes have been optimised at the MP2/aug-cc-pVTZ level and the stabilisation energies are calculated at the CCSD(T)/aug-cc-pVTZ level. Halogen bond complexes of [CCl4 single bond(H2O)n] are more stable compared to the hydrogen bond complexes. Stability of halogen and hydrogen bond complexes of [CCl4 single bond(H2S)n] are comparable. The Rayleigh scattering intensity of these complexes have been investigated for the first time. Rayleigh scattering intensity increases with the number of H2O and H2S molecules in the complexes. The Rayleigh scattering intensity of the halogen bond complexes are higher compared to the hydrogen bond complexes.
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    Matrix-isolation FTIR spectroscopic study and quantum chemical calculations of 1:1 adduct of CHCl3 and C2H5OH in N2 matrix
    (Elsevier, 2024-06) Chakraborty, Amrita; Chakraborty, Shamik
    [Image 1-Image 2] mixture is a common binary solvent used in industries, organic synthesis, lipid extraction, drug extraction, etc. The purpose of this study is to have a molecular level understanding of the interaction of Image 1 with Image 2. The experiments have been carried out in low temperature Image 3 matrix using Fourier Transform Infrared spectroscopy. Electronic structure calculations have been performed to identify the possible binding motifs between Image 1 and Image 2. Three minima have been obtained on the dimer potential energy surface stabilised by Image 4 and Image 5 hydrogen bond, and Image 6 halogen bond interactions. Formation of more than one complexes have been confirmed using the experimental and simulated IR spectra. Energy decomposition analysis and Natural bond orbital analysis have been performed to understand the nature of interaction and the driving force for complexation. This is one of the first reports where separate complexes have been identified between Image 1 and anti and gauche conformers of Image 2 in the low temperature matrix.
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    Competition between the hydrogen bond and the halogen bond in a [CH3OH–CCl4] complex: a matrix isolation IR spectroscopy and computational study
    (RSC, 2020) Chakraborty, Shamik; Chakraborty, Amrita
    Methanol (CH3OH) is the simplest alcohol and carbon tetrachloride (CCl4) is widely used as a solvent in the chemical industry. CH3OH and CCl4 are both important volatile substances in the atmosphere and CCl4 is an important precursor for atmospheric ozone depletion. Moreover, mixtures of CH3OH and CCl4 are an important class of non-aqueous mixtures as they exhibit a large deviation from Raoult's law. The specific interaction between CH3OH and CCl4 is not yet investigated experimentally. The interaction between CH3OH and CCl4 at the molecular level can be twofold: hydrogen bond (O–H⋯Cl) and halogen bond (C–Cl⋯O) interaction. One halogen bonded minimum and two hydrogen bonded minima are identified in the dimer potential energy surface. Herein, the 1 : 1 complex of [CH3OH–CCl4] has been characterised using matrix-isolation infrared spectroscopy and electronic structure calculations to investigate the competition between hydrogen bonded and halogen bonded complexes. Vibrational spectra have been monitored in the C–Cl, C–O, and O–H stretching regions. The exclusive formation of halogen bonded 1 : 1 complexes in argon and nitrogen matrices is confirmed by a combination of experimental and simulated vibrational frequency, stabilisation energy, energy decomposition analysis, and natural bond orbital and atoms-in-molecules analyses. This investigation helps to understand the specific interactions in the [CH3OH–CCl4] mixture and also the possibilities of formation of halogen bonded atmospheric complexes that may influence the atmospheric chemical activities, and enhance aerosol formation and deposition of CCl4.