Concentration-dependent Raman Study Research Articles

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

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.

Investigation of inter-molecular hydrogen bonding in the binary mixture (acetone + water) by concentration dependent Raman study and ab initio calculations

This paper reports that vibrational spectroscopic analysis on hydrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6–311+G(d,p) basis set. Changes in wavenumber position and linewidth (fullwidth at half maximum) have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.

Investigation of ν(N [sbnd]H) and ν(C [sbnd]N) stretching modes of propylamine (C 3H 7NH 2) in a binary system C 3H 7NH 2 + CH 3OH via concentration dependent Raman study and ab initio calculations

Raman spectra of propylamine (C 3H 7NH 2) and its binary mixtures, C 3H 7NH 2 + CH 3OH with varying mole fractions of the reference system, C 3H 7NH 2, C were recorded in two widely apart wavenumber regions, 3100–3600 cm −1 and 1225–1325 cm −1. In the former region, the two Raman bands at ∼3305 and ∼3326 cm −1, obtained after the line shape analysis, which were assigned to symmetric ν(N H) and anti-symmetric ν(N H) stretching modes, respectively, show a downshift upon dilution. However, whereas the ν(N H) anti-symmetric mode shows a shift of 18.6 cm −1, the ν(N H) symmetric mode shows a much smaller shift (5.7 cm −1) between neat liquid and high dilution, C = 0.1. This aspect has been explained using the optimized geometries calculated employing ab initio theory (MP2 level) for the neat C 3H 7NH 2 and its different hydrogen-bonded complexes. The linewidth versus concentration plot for the ν(N H) anti-symmetric stretching mode, however exhibits a distinct maxima at C = 0.4, which has been explained as a slight departure from the concentration fluctuation model. In the latter region, a symmetric peak is observed, which corresponds to ν(C N) stretching mode, which shows an upshift upon dilution and an almost linear concentration dependence. This has also been explained in terms of the parameters obtained from the optimized geometries of the different hydrogen-bonded complexes.

Hydrogen bonding in binary mixtures of tetrahydrofuran and water: a concentration dependent Raman study and ab-initio calculations

Hydrogen bonding in binary mixtures of tetrahydrofuran and water: a concentration dependent Raman study and ab-initio calculations

Analysis of the symmetric and anti-symmetric N-H stretching modes of n-propylamine in binary mixtures with methanol: a concentration dependent Raman study and ab-initio calculations

Analysis of the symmetric and anti-symmetric N-H stretching modes of n-propylamine in binary mixtures with methanol: a concentration dependent Raman study and ab-initio calculations

Investigation of hydrogen bonding and self-association in neat HCONH 2 and the binary mixture (HCONH 2+CH 3OH) by concentration dependent Raman study and ab initio calculations

Raman spectra of neat formamide (HCONH 2) and its binary mixture (HCONH 2+CH 3OH) with hydrogen donor solvent, methanol (CH 3OH) were investigated using a sensitive scanning multichannel detection scheme, which is simultaneously more precise also, especially when the observed Raman line profile has multiple component bands. The spectra in the two regions, namely 1200–1500 and 1500–1800 cm −1 were recorded with varying mole fractions of the reference molecule, HCONH 2, from 0.1 to 0.9. The spectra in the region 1200–1500 cm −1 show a broad band at ∼1312 cm −1, which shows a peculiar concentration dependence, and a relatively sharp peak at ∼1392 cm −1, whose peak position is not influenced by concentration. The spectra in the region 1500–1800 cm −1 also show two peaks, one at ∼1593 cm −1 and the other one at ∼1668 cm −1 which are assigned to NH 2 bending and ν(CO) stretching vibrations, respectively. Both these Raman bands show an appreciable upshift of ∼15–20 cm −1 and the one at ∼1668 cm −1 has also a distinct asymmetry towards higher wavenumber. The optimized geometries and vibrational wavenumbers of various normal modes for neat formamide as well as its hydrogen-bonded complexes were also calculated using ab initio theory at the MP2 level. The results have been used to understand and explain the concentration dependent changes in the spectral features in terms of hydrogen bonding and self-association.