3725-31-3Relevant academic research and scientific papers
Rotationally resolved electronic spectra of trans trans-octatetraene and its derivatives
Pfanstiel
, p. 2337 - 2347 (1999)
Described herein are the rotationally resolved one-photon fluorescence excitation spectra of several vibronic bands in the S1 ← S0 electronic transitions of three linear polyenes in the gas phase, 1,3,5,7-octatetraene (OT), 1,3,5,7-nonatetraene (NT), and 2,4,6,8-decatetraene (DT). Several of the spectra are significantly perturbed by an apparent centrifugal distortion in the S1 state of OT, owing to the high frequency of rotations parallel to a and the low frequency of an in-plane bending mode (v48), by Coriolis coupling in the S1 state of NT, involving v48 and a nearby methyl torsional level, and by torsion-rotation coupling in the S1 states of NT and DT, owing to a significant reduction in the excited-state torsional barrier(s) compared to the ground state. Nonetheless, the inertial parameters of eight different S0 and S1 vibronic levels have been determined, from which it is concluded that the carriers of the spectra are in all cases the transjrans isomers. The important role of V48 as a promoting mode for S1 - S2 vibronic coupling, the source of the S1 - S0 oscillator strength, is confirmed. Finally, the measured differences in the rotational constants of the S0 and S1 states (e.g., ΔA = 2532, ΔB = -11.7, and ΔC = -11.0 MHz for the vibronic origin of OT) provide new information about the changes in geometry that occur when the photon is absorbed.
High-resolution one and two photon excitation spectra of trans,trans-1,3,5,7-octatetraene
Granville, Mark F.,Holtom, Gary R.,Kohler, Bryan E.
, p. 4671 - 4675 (1980)
One and two photon excitation spectra for the lowest energy singlet transition (21Ag 11Ag) of trans,trans-1,3,5,7-octatetraene in n-octane at 4.2 K(0-0 at 28 561 cm-1) have been measured and analyzed.The one photon spectrum is found to be vibronically induced while the two photon spectrum is electronically allowed.The contribution of the higher lying 11Bu 11Ag transition (0-0 at approximately 32 100 cm-1) to the observed two photon excitation spectrum is found to be negligible allowing vibrational overtones of the 21Ag 11Agsystem to be observed.On the bases of frequency, intensity, and one or two photon allowedness, 128 measured lines are assigned as combination of 4 antisymmetric and 11 symmetric normal modes.
Excited-state dynamics of all-trans-1,3,5,7-octatetraene in solution. Direct observation internal conversion from the S2 to S1 state and relaxation processes in the S1 state
Ohta, Kaoru,Naitoh, Yukito,Tominaga, Keisuke,Yoshihara, Keitaro
, p. 3973 - 3980 (2007/10/03)
Femtosecond transient absorption spectroscopy was used to study the excited-state dynamics of the S2 (1 1Bu) state all-trans-1,3,5,7-octatetraene in solution. The sample was excited at 267 nm and probed at eleven different wavelengths from 340 to 540 nm. Combined with the picosecond fluorescence spectroscopy, this study allows direct observation of the initial excited-state dynamics of all-trans-1,3,5,7-octatetraene and the subsequent relaxation process to the ground state. Transient absorption signals decaying on time scales of about 0.4 ps were seen at wavelengths longer than 480 nm. These absorptions are assigned to an Sn-S2 transition, indicating that internal conversion from the S2 to S1 state takes place on a 400-fs time scale. The transient absorption signals observed at shorter wavelengths, which correspond to the Sn-S1 transition, decay on a picosecond to subnanosecond time scale. A weak fluorescence at about 300-350 nm, originating from the S2 state, and a strong fluorescence at about 350-500 nm, from the S1 state, were observed. The time profile of the S2 fluorescence signal is almost equal to the instrument response function, and the lifetime is estimated to be faster than 5 ps. This observation is consistent with the results of transient absorption signals. The S1 fluorescence signal consists of two decay components. The average lifetimes are 0.88 ns in acetonitrile and 2.0 ns in n-hexane. Nonexponential decay of the fluorescence may result from an equilibrium mixture of the fluorescent state and the conformationally relaxed state. The fluorescence intensity ratio of S2 to S1 in solution is much different from that observed in the gas phase. This means that the efficiency of internal conversion increases significantly in solution because of the solute-solvent interactions that are absent in the gas phase. We discuss differences in the excited-state dynamics between 1,3,5-hexatriene and 1,3,5,7-octatetraene.
Synthesis and Characterization of Representative Octa-1,3,5,7-tetraenes and Deca-1,3,5,7,9-pentaenes
Spangler, Charles W.,Little, David A.
, p. 2379 - 2386 (2007/10/02)
Several representative conjugated linear tetraenes and pentaenes were prepared by a variety of synthetic methods including Wittig condensation, 1,8-Diazabicycloundec-7-ene (DBU)-induced dehydrobromination, and Hofmann elimination.For the preparation of (E,E)- and (Z,E)-octa-1,3,5,7-tetraene, the Hofmann elimination sequence is by far the most convenient method by synthesis, while DBU-induced dehydrobromination of (E,E)-4-bromonona-1,5,7-triene, produces excellent yields of (E,E,E)- and (3Z,5E,7E)-nona-1,3,5,7-tetraene.Deca-1,3,5,7,9-pentaene can be produced by several methods, but not in high yield.Undeca-1,3,5,7,9-pentaene and trideca-1,3,5,7,9,11-hexaene can also be prepared in low yield by the Wittig reaction.All the polyenes produced in this study polymerize rapidly in the crystalline state.
Preparation of (E)-1,3,5-Hexatriene and (3E,5E)-1,3,5,7-Octatetraene by the Palladium Catalyzed Elimination of Acetic Acid form Allylic Acetates
Yamamoto, Keiji,Suzuki, Shigeaki,Tsuji, Jiro
, p. 2541 - 2542 (2007/10/02)
Palladium complex-catalyzed elimination of acetic acid from (2E,4E)-2,4-hexadienyl acetate and (2E,4E,6E)-2,4,6-octatrienyl acetate afforded, respectively, the title conjugated polyenes stereoselectively.
