J Koster

Bio: J Koster is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Hydrogen bond & Raman spectroscopy. The author has an hindex of 1, co-authored 1 publications receiving 47 citations.

Hydrogen-bonding between pyrimidine and water: a vibrational spectroscopic analysis.

Abstract: We present an experimental and a theoretical study on hydrogen-bonding between pyrimidine and water as the H-donor. The degree of hydrogen-bonding in this binary system varies with mixture composition. This was monitored experimentally by polarization-resolved linear Raman spectroscopy with the pyrimidine ring breathing mode ν1 as a marker band. A subsequent quantitative line shape analysis of the isotropic Raman intensity for 24 pyrimidine/water mixtures clearly revealed a splitting into three spectral components upon dilution with water. The two additional peaks have been assigned to distinct groups of hydrogen-bonded species that differ in the number of pyrimidine nitrogen atoms (N) involved in hydrogen-bonding to water hydrogen atoms (H). From the integrated Raman intensities for “free” and “hydrogen-bonded” pyrimidine, a concentration profile for these species was established. Our assignments and interpretations are supported by quantum mechanical calculations of structures and by vibrational spectra...

Effects of Hydrogen Bonding on Vibrational Normal Modes of Pyrimidine

Abstract: The effects of weak intermolecular interactions on 10 vibrational normal modes of pyrimidine are investigated by Raman spectroscopy and electronic structure computations. Hydrogen-bonded networks o...

Charge transfer and blue shifting of vibrational frequencies in a hydrogen bond acceptor.

Abstract: A comprehensive Raman spectroscopic/electronic structure study of hydrogen bonding by pyrimidine with eight different polar solvents is presented. Raman spectra of binary mixtures of pyrimidine with methanol and ethylene glycol are reported, and shifts in ν1, ν3, ν6a, ν6b, ν8a, ν8b, ν9a, ν15, ν16a, and ν16b are compared to earlier results obtained for water. Large shifts to higher vibrational energy, often referred to as blue shifts, are observed for ν1, ν6b, and ν8b (by as much as 14 cm–1). While gradual blue shifts with increasing hydrogen bond donor concentration are observed for ν6b and ν8b, ν1 exhibits three distinct spectral components whose relative intensities vary with concentration. The blue shift of ν1 is further examined in binary mixtures of pyrimidine with acetic acid, thioglycol, phenylmethanol, hexylamine, and acetonitrile. Electronic structure computations for more than 100 microsolvated structures reveal a significant dependence of the magnitude of the ν1 blue shift on the local microsol...

Investigation of hydrogen bonding in neat dimethyl sulfoxide and binary mixture （dimethyl sulfoxide water） by concentration-dependent Raman study and ab initio calculation

Abstract: In this study, our vibrational spectroscopic analysis is made on hydrogen-bonding between dimethyl sulfoxide and water comprises both experimental Raman spectra and ab initio calculations on structures of various dimethyl sulfoxide/water clusters with increasing water content. The Raman peak position of the v(S=O) stretching mode of dimethyl sulfoxide serves as a probe for monitoring the degree of hydrogen-bonding between dimethyl sulfoxide and water. In addition, the two vibrational modes, namely, the CH3 symmetric stretching mode and the CH3 asymmetric stretching mode have been analysed under different concentrations. We relate the computational results to the experimental vibrational wavenumber trends that are observed in our concentration-dependent Raman study. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the nature of the hydrogen bonding and the structures of the hydrogen-bonded complexes studied.

Hydrogen bonding in different pyrimidine–methanol clusters probed by polarized Raman spectroscopy and DFT calculations

Abstract: We report on the hydrogen bonding between pyrimidine (Pd) and methanol (M) as H-donor in this study. Hydrogen bonds between pyrimidine and methanol molecules as well as those between different methanol molecules significantly influence the spectral features at high dilution. The ring-breathing mode ν1 of the reference system Pd was chosen as a marker band to probe the degree of hydrogen bonding. Polarized Raman spectra in the region 970–1020 cm−1 for binary mixtures of (pyrimidine + methanol) at 28 different mole fractions were recorded. A Raman line shape analysis of the isotropic Raman line profiles at all concentrations revealed three distinct spectral components at mole fractions of Pd below 0.75. The three components are attributed to three distinct groups of species: ‘free Pd’ (pd), ‘Pd with low methanol content’ (pd1) and ‘Pd with high-methanol content’ (pd2). The two latter species differ considerably in the pattern and the strengths of the hydrogen bonds. The results of density functional theory calculations on structures and vibrational spectra of neat Pd and eight Pd/M complexes with varying methanol content support our interpretations of the experimental results. A nice spectra–structure correlation for the different cluster subgroups was obtained, similar to earlier results obtained for Pd and water. Apart from N···H and O···H hydrogen bonds between pyrimidine and methanol, O···H hydrogen bonds formed among the methanol molecules in the cluster at high methanol content also play a crucial role in the interpretation of the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.