The Spectroscopy and Photophysics of Styrene

Abstract

<p>The infrared and Raman spectra of liquid styrene, styrene-d₃, styrene-d₅ and styrene-d₈ have been analyzed. Assignments have been made for the 42 normal modes of vibration in each molecule. The fluorescence and fluorescence excitation spectra of solutions of the four isotopic styrenes have been studied in a polycrystalline methylcyclohexane matrix at 77 K. Vibrational analysis of the fluorescence spectra indicate that the Ā state of styrene is planar. The Ā-X transition moment is a-axis polarized, in contrast to what has been found in several other monosubstituted benzenes. The fluorescence excitation spectra have also been vibrationally analyzed, and several excited state fundamental frequencies have been assigned.</p> <p>The fluorescence decay time and quantum yield of each of the four styrenes have been determined, in cyclohexane at room temperature and in 3-methylpentane at room temperature and at 77 K. The radiative rate constant is essentially independent of isotope, solvent and temperature. The non-radiative rate constant decreases only very slightly upon deuteration and by about 50% upon cooling. These results are compared with similar data of a related compound, trans-stilbene.</p> <p>Triplet-triplet electronic energy transfer studies at 77K using acetophenone as sensitizer indicate the presence of rapid non-radiative decay pathway from triplet styrene.</p>