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Abstract: We report the effects of methanol, pyridine, diethylamine, dichloromethane, acetonitrile, bromine and NO2 vapours on the Raman and infrared absorption spectra of zinc tetraphenylporphine thin films by recording their spectra before and after exposure with chemical vapours. Positions of some vibrational bands show detectable change on exposure. Changes in the intensity of some vibrational bands of the thin films have also been observed on exposure. Coordination of vapours molecules at the zinc ion and subsequent charge transfer are responsible for the shift in the vibrational bands. Density functional theory calculations have been carried out to determine the probable geometric structures of the porphyrin–vapour complexes. Calculated geometric structures show in-plane and out-of-plane distortions in the porphyrin macrocycle. Calculations also result in charge transfer between vapour and porphyrin molecules. [Copyright &y& Elsevier]

Abstract: We report the effects of chemical vapours on the Raman and infrared absorption spectra of α crystalline nickel phthalocyanine thin films. Transmission electron micrograph of the thin films suggests presence of nano-sized particles of nickel phthalocyanine in the thin film. Some vibrational bands show changes in their positions and/or intensities on exposure of thin films with chemical vapours. These changes have been interpreted on the basis of interactions of the vapours molecule with the central nickel ion and other peripheral atoms of the phthalocyanine ring. Density functional theory (DFT) calculations have been carried out to determine the probable geometric structures of the complexes of vapour and phthalocyanine molecules. Calculated geometric structures show in-plane and out-of-plane distortions in the phthalocyanine molecule. Calculations further suggest charge transfer between vapour and phthalocyanine molecules. [Copyright &y& Elsevier]

Abstract: The present work reports vibrational spectra and density functional theory calculations for chloranil, imidazole and their complexes. The experimentally observed infrared and Raman bands have been assigned with the help of calculated vibrational frequencies and potential energy distribution analysis. Some bands of chloranil and imidazole have been found to shift on the complex formation due to partial electronic charge transfer from imidazole to chloranil. The charge transfer between these molecules is also corroborated by the electronic absorption spectroscopy and calculations. The theoretical values of the interaction energy of various possible chloranil–imidazole interactions suggest that the two molecules interact preferably via N and H atoms of imidazole and Cf chloranil with their molecular planes almost perpendicular to each other. [Copyright &y& Elsevier]

Abstract: We report Raman and infrared spectra of rhodamine 6G dye in different experimental conditions. Positions of some of the observed vibrational bands show noticeable change in the solvents. The bands, which shift, have contributions from the vibrational motion of nitrogen atoms of the ethoxyamine groups, oxygen atom of the ethoxycarbonyl group attached to the phenyl ring and the atoms of the xanthene ring. These shifts arise due to simultaneous interaction of a number of solvent molecules at nitrogen and hydrogen atoms of ethoxyamine, oxygen atom of ethoxycarbonyl and the central oxygen atom of the xanthene ring of the dye molecule. Density functional theory calculations of molecular parameters and atomic charge densities of rhodamine 6G and most probable rhodamine 6G–methanol complexes also support these interactions. Methanol and dimethylformamide also interact electrostatically with the positively charged nitrogen atom of the dye molecule. [Copyright &y& Elsevier]

Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet–visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet–visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

We report here the vibrational and structural analysis of alpha-tocopherol. The vibrational analysis has been accomplished experimentally by infrared and Raman spectroscopic techniques and theoretically by density functional theory. Two conformers of alpha-tocopherol have been optimized with the help of density functional theory. Energy minimized structures have been further used for vibrational frequencies calculations. Calculated values of molecular parameters of both the conformers have been comparable with the available experimental values in literature. All the observed vibrational bands have been assigned with the help of potential energy distribution calculations and intensity patterns of the simulated spectra. The ultraviolet–visible spectrum has been reported in wavelength range of 200 nm–500 nm. Observed ultraviolet–visible bands have been assigned to various electronic transitions, which have also been calculated using time dependent density functional theory. [ABSTRACT FROM AUTHOR]

Highlights: [•] IR spectra of melatonin in 3600–2700 and 1700–70cm−1 regions are reported. [•] Raman spectra recorded with 488 and 632.8nm excitations are also included. [•] Structure optimized with DFT. Vibrational frequencies and PED calculated. [•] IR and Raman bands assigned. N H stretch frequency mismatch is due to H-bonding. [•] UV–Vis spectrum recorded and compared with spectra calculated from TD-DFT method. [Copyright &y& Elsevier]

Abstract: In the present work, we have studied the effect of pyridine on the zinc phthalocyanine by recording the infrared absorption and X-ray diffraction spectra with and without pyridine. In the presence of pyridine phase of the crystalline zinc phthalocyanine changes from β to α. Some infrared bands show changes in their positions and/or intensities. These changes have been interpreted on the basis of coordination of the pyridine molecule with the central zinc ion. Coordinated pyridine transfers some of its charge to the π electron system of the phthalocyanine ring through zinc ion. Pyridine molecule also distorts the phthalocyanine molecule by pulling zinc ion out of the phthalocyanine plane. Density functional theory also confirms the ligation of pyridine molecule at the fifth coordination site of the central metal ion. [Copyright &y& Elsevier]