V. Zhelyaskov

Concentration Raman study of intramolecular, intermolecular and Fermi resonance interactions in the OH stretching spectra of dilute solutions of HDO in D2O using Fourier deconvolution technique

The Raman OH stretching spectra of dilute solutions of H20 in D20, from 100 mole per cent to 10 mole per cent concentration, are studied. For the first time the decoupled OH spectra are treated by means of Fourier deconvolution technique. The resolved components in the isotropic and anisotropic spectra are analysed in terms of a model. The frequency and intensity behaviour of the components confirm the suggestion, that strong decoupling of all vibrations with dilution takes place. It is shown that intramolecular and Fermi resonance interactions are negligibly small under 20 mole per cent concentration. On the contrary, a significant intermolecular interaction, with a coupling constant equal to 42 cm−1, is observed down to concentrations of 10 mole per cent. The latter is explained with the significant number of the HDO molecules, which have at least one HDO, or H20 neighbour at this concentration. In respect to intermolecular interaction a dilution of H20 in D20 down to 10 mole per cent concentration is e...

Raman study of 12-crown-4, 15-crown-5, 18-crown-6 and their complexation with metal cations using Fourier deconvolution of CH stretching spectra

Abstract The Raman CH stretching spectra of 12-crown-4, 15-crown-5 and 18-crown-6 and their complexes with some metal cations— Li+, Na+, K+ and Cu+ in water solutions are studied. For the first time Fourier deconvolution is applied to resolve the overlapped components in the corresponding isotropic and anisotropic spectra. A model is introduced which explains the variety of components in the spectra by means of splitting of the unperturbed CH stretching frequency owing to intramolecular interactions and Fermi resonance. The coupling constants of these interactions, as well as all parameters according to the model, are calculated for studied crowns and their complexes. The differences in the number and intensity of the resolved components in the spectra of the various crowns are explained with the corresponding differences in the coupling constants and model parameters. It is established that complexation leads to some increase in the unperturbed stretching frequency, probably owing to the increase in strain of the crown molecule. It is concluded that 15-crown-5 forms 2:1 and 1:1 complexes with K+ and Na+ cations respectively and 12-crown-4 forms a 2:1 complex with the Na+ cation.

Fluorescence of the benzophenone ketyl radical: solvent effects

Abstract The fluorescence of the benzophenone kethyl radical (BKR) was studied in different solvents by a double-pulse excitation technique using two synchronized lasers. Fluorescence quantum yields of the BKR were determined employing a new technique suitable for measurement of short-lived transients with low level emission. By analysing the fluorescence spectral shape and the values of the quantum yields in the different solvents it can be concluded that charge transfer complexes are formed in the excited doublet state of BKR, with the molecules of the solvents exibiting electron-donor properties.

Raman Temperature Study of 12-Crown-4 Using Fourier Deconvolution of CH Stretching Spectra

Abstract The Raman CH Stretching spectra of 12C4 in water solution, for temperatures from 5 to 80 °C, are studied. For the first time, Fourier deconvolution technique is applied to resolve the overlapped components in the corresponding isotropic and anisotropic spectra. The results are treated by means of a model. explaining the variety of resolved components with a splitting of the unperturbed CH stretching vibration. owing to intramolecular interactions. The temperature behaviour of the coupling constants of these interactions is discussed.

Raman study of the “free” OH groups in H2O-H2O2 mixtures using Fourier deconvolution technique

Abstract The frequency behaviour of the component at 3635 cm−1 in the Raman OH stretching spectrum of water, responsible for the so called “free· OH groups is studied for different concentrations of H2O2 in H2O up to 30 mole%. The water Raman band is decomposed by Fourier deconvolution technique (FDT) in the isotropic and anisotropic case. The increase in H2O concentration leads to a decrease in the frequency of the resolved component in both kind of spectra resulting in the apparent gradual vanishing of the high frequency shoulder in the original spectrum. The small frequency shift (35 cm−1) shows that “free” OH oscillators of water form weak hydrogen bonds with H2O2 and supports the idea of bifurcated H bonded weak associates of water molecules.

Temperature study of the intramolecular interactions in 15-crown-5 and 18-crown-6

Abstract The Raman CH stretching spectra of 15-crown-5 and 18-crown-6 in water solution are studied in the temperature interval 5–80°C. The method of Fourier deconvolution is applied to resolve the overlapped bands in the complex isotropic and anisotropic spectra. The intramolecular coupling constants and the unperturbed CH stretching frequency are calculated for all studied temperatures. The temperature dependencies are discussed in comparison with the temperature dependencies for 12-crown-4 obtained previously.

Temperature dependences of intra- and inter-molecular interactions in water and 12-Crown-4 - a comparison

Abstract Intra-, inter-molecular (inter-bond) and Fermi resonance interactions in water and 12-Crown-4 are considered. The temperature dependences of the corresponding interaction constants, recently published in literature (Refs. 1,2), are compared. It is shown that the main reason for the existing differences in the temperature behaviour of the intramolecular and Fermi resonance interactions between water and crown is the presence of strong temperature dependent H bonds between water molecules and an absence of such or similar bonds between crown molecules. The similarity in the temperature behaviour of the intermolecular (interbond) interaction in water and in crown is because of the similar mechanisms of the intermolecular (interbond) coupling.