Symmetry breaking and spectra of diphenyloctatetraene in n-alkanes

Abstract

Articles you may be interested inElectronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study J. Chem. Phys. 143, 204304 (2015); 10.1063/1.4935578The elusive S 2 state, the S 1/S 2 splitting, and the excimer states of the benzene dimer J. Chem. Phys. 142, 234306 (2015) One-and two-photon excitation spectra, as well as absorption and emission spectra of diphenyloctatetraene ͑DPOT͒ in n-alkanes are investigated at low temperatures. For DPOT in n-octane we report on the measurements of one-photon excitation and emission spectra and for DPOT in n-tetradecane ͑TD͒ on the measurements of one-and two-photon excitation spectra and emission spectra. The spectra are governed by the transitions between the electronic ground (S 0 ) and the two lowest electronic excited singlet states (S 1 ,S 2 ). The interpretation is based on allowed transitions and transitions induced by the S 1 -S 2 coupling due to Herzberg-Teller promoting modes or due to static lattice-induced distortions of DPOT. A single noncentrosymmetric site is observed for DPOT in n-octane. For DPOT in TD a centrosymmetric and a noncentrosymmetric site are reported. The analysis indicates that there is a dynamical equilibrium in the population of these two sites. The experimental data are quantitatively studied by comparison with simulated spectra. The simulation calculations are based on the coupling between nonadiabatic S 1 and S 2 states, harmonic modes, and suitable transition moments and line-shape functions. For DPOT in TD the calculations reveal an interesting interference pattern in the vibronic progressions observed in two-photon excitation spectra.

Thermal behavior of pentachlorophenyl methacrylate–acrylonitrile copolymers

“…It is noteworthy that both 3 and 4 exhibited, in addition to the absorptions due to respective oligoaryl chromophores, tailing at longer wavelengths, which could be assigned to a symmetry‐forbidden transition 2d. The observation of the partially allowed transition could possibly be attributed to electron‐vibration interactions 2d.…”

“…Accordingly, a partial negative charge around a bridging double bond might be generated after photoexcitation 3. 17 It seems likely that the vibronic coupling might be responsible for such partially allowed charge‐transfer transitions 2d…”

“…The electron localization in the excited state of the phenylenevinylene‐based conjugated polymers has been rationalized by a conformational kink mechanism 5. In addition, a dynamic equilibrium in the population of a centrosymmetric and a noncentrosymmetric site has been used to elucidate the excitation properties of diphenyloctatetraene in n ‐tetradecane 2d…”

Electron–phonon coupling in two-photon spectral gratings: role of molecular symmetry

“…This fact can be explained if we consider selection rules for pure electronic transition in this centrosymmetrical molecule. Since we are dealing with gerade2ungerade; S 0 2S 1 one-photon transition, it must be strongly forbidden for pure electronic TPA [4][5][6][7][8][9][10]. However, TPA with creation of phonons (electron-phonon transition, building up PW in homogeneous TPA spectrum) can be allowed through Herzberg-Teller mechanism.…”

“…Intuitively, this effect implies the presence of narrow zero-phonon lines (ZPL) in TPA transition. TPA pure electronic ZPLs were shown for several molecules, including centrosymmetric [4][5][6][7][8][9][10] and non-centrosymmetric ones [11,12].…”