Resonance Raman and Absorption Spectroscopy of the Lowest Triplet State of 1,3,5-Hexatriene and Deuteriated Derivatives at 183 K: Molecular Structure in the T1 State

Article abstract of DOI:10.1021/j100171a028

Time-resolved resonance Raman (RR) spectra of the lowest excited triplet state T₁ of (E)-1,3,5-hexatriene, (E)-3-deuterio-1,3,5-hexatriene, and (E)-1,1-dideuterio-1,3,5-hexatriene are obtained at 183 K.The T₁ potential energy surface (PES), determining energy minima, equilibrium geometries, frequencies, and normal modes of vibration, is calculated, and RR intensities are obtained on the basis of the Franck-Condon mechanism.By comparison with the calculated spectra, the observed RR spectra are assigned to an equilibrium mixture of planar E and Z species in the T₁ state.The relative intensity of the E and Z bands at temperatures between 293 and 183 K gives an upper limit of 0.22 kcal/mol for the energy difference between the planar E and Z forms.Time-resolved triplet-triplet absorption measurements as a function of temperature between 296 and 183 K yield a frequency factor A of 1.6x10⁷ s^-1 and an apparent activation energy E_a of 0.7 kcal/mol for the decay of the T₁ state.Consequently, an upper limit of 0.7 kcal/mol above the planar E and Z geometries is established for the possible local energy minimum at the twisted geometry.On the basis of these data, a PES is proposed for the T₁ state of 1,3,5-hexatriene with respect to torsion around the central CC bond and the C₂C₃ and C₄C₅ bonds.

Full text of DOI:10.1021/j100171a028

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Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.