• Laser Raman spectroscopic study of photoreaction dynamics inp-chloro cinnamic acid crystal

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    • Keywords


      Solid state photoreaction; phonon-mediated reaction; mode softening; p-chlorocinnamic acid crystal

    • Abstract


      Raman phonon spectroscopy has been used to study photodimerization reaction inp-chloro cinnamic acid (pCCA) crystal. The β-form of the crystal yields the 4,4′-dichloro-β-truxinic acid dimer. Six distinct low frequency phonon bands are observed in thepCCA monomer crystal. On reaction progress, these bands show a monotonic shift to lower frequencies and broaden out. Finally, in the dimer crystal the phonon spectrum shows two weak broad bands. These results suggest that the reaction is homogeneous in the initial stages and, as the product concentration increases, the lattice becomes highly disordered. The reactant and the product were characterised by infrared and Raman spectroscopy. The disappearance of aliphatic C=C bond stretching vibration and appearance of cyclobutane ring deformation and cyclobutane ring-breathing vibrations on reaction confirm photodimerization by cyclobutane ring formation. The large Stoke's shift between the absorption and emission band suggest strong exciton-phonon coupling in the monomer lattice. This reaction seems to be phonon-mediated.

    • Author Affiliations


      Subhasis Chakrabarti1 M Gantait1 T N Misra1

      1. Spectroscopy Department, Indian Association for the Cultivation of Science, Jadavpur, Calcutta - 700 032, India
    • Dates

  • Journal of Chemical Sciences | News

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