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 T sub 1 state

Journal Article · Thu Sep 05 00:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100171a028· OSTI ID:5225623

Langkilde, F W ^[1]; Wilbrandt, R; Moeller, S ^[2]; Brouwer, A M ^[3]; Negri, F; Orlandi, G ^[4]

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1. Royal Danish School of Pharmacy, Copenhagen (Denmark)
2. Risoe National Lab., Roskilde (Denmark)
3. Univ. of Amsterdam (Netherlands)
4. Univ. of Bologna (Italy)

Time-resolved resonance Raman (RR) spectra of the lowest triplet state T{sub 1} 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 T{sub 1} 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 T{sub 1} 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 1.6 C 10{sup {minus}7} s{sup {minus}1} and an apparent activation energy E{sub a} of 0.7 kcal/mol for the decay of the T{sub 1} 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 T{sub 1} state of 1,3,5-hexatriene with respect to torsion around the central CC bond and the C{sub 2}C{sub 3} and C{sub 4}C{sub 5} bonds.

• OSTI ID: 5225623
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:18; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
ABSORPTION SPECTROSCOPY
ACTIVATION ENERGY
ALKENES
ARRHENIUS EQUATION
CHEMICAL REACTIONS
DATA
DEUTERIUM
ELECTRONIC STRUCTURE
ENERGY
EQUATIONS
EXPERIMENTAL DATA
FRANCK-CONDON PRINCIPLE
HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
ISOMERIZATION
ISOTOPES
LABELLED COMPOUNDS
LASER SPECTROSCOPY
LIGHT NUCLEI
MATHEMATICAL MODELS
MOLECULAR STRUCTURE
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OSCILLATION MODES
RAMAN SPECTRA
RAMAN SPECTROSCOPY
RESONANCE
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
THEORETICAL DATA
THERMODYNAMICS
TIME DEPENDENCE