Solvent−Solute Interactions Probed by Picosecond Transient Raman Spectroscopy:  Vibrational Relaxation and Conformational Dynamics in S₁trans-4,4‘-Diphenylstilbene

Abstract

We present the S1 picosecond transient Raman spectra of trans-4,4‘-diphenylstilbene (DPS) obtained at excitation wavelengths of 287 and 310 nm and probe wavelengths of 630 and 660 nm. We compare spectra at different pump and probe wavelengths in order to evaluate the role of conformational dynamics and vibrational relaxation in S1 DPS. In this study, we find that dioxane and methylene chloride accept excess vibrational energy from the photoexcited solute in a different manner. We attribute this variation either to a difference in the local solvent structure or to the difference in the density of states between methylene chloride and dioxane. We also find that the relative intensities of certain bands demonstrate a dependence upon the pump and probe wavelengths. From these data, we have established that the change in relative intensity with delay is a marker for the dynamical shift in the S1 potential energy surface. The dependence of this dynamical change on excitation wavelength demonstrates that we are examining a “nonstationary” state that evolves on a 10−50 ps time scale.

ESIPT and Photodissociation of 3-Hydroxychromone in Solution: Photoinduced Processes Studied by Static and Time-Resolved UV/Vis, Fluorescence, and IR Spectroscopy

“…Component A 2 in MCH- d 14 can be attributed to vibrational cooling because it displays qualitatively the blue shift of bands assigned to S 1 ′ by a pairing of a high-energy negative lobe and a low-energy positive lobe at positions with S 1 ′ absorption. Although a global fit gives solely a monoexponential approximation of the nonexponential vibrational cooling process, global fitting has already been successfully used to describe vibrational cooling/relaxation processes in the IR spectral region. − A similar pattern was observed in the transient IR data of 3-HF dissolved in ACN- d 3 and MCH- d 14 with time constants of 12–17 and 13 ps (from a global fit of 3-HF/MCH- d 14 data; not published), respectively . The time constant found for 3-HC is thus longer than that of 3-HF, which might be due to the smaller extent of low-energy vibrational modes like the phenyl torsion of 3-HF that couple with solvent modes.…”

Transient IR spectroscopy and ab initio calculations on ESIPT in 3-hydroxyflavone solvated in acetonitrile

“…Such characteristic patterns have been observed and described e.g., for azobenzene 64 and similar processes have been reported for a number of molecular systems in the condensed phase. [65][66][67][68] Signals of A 2 coinciding with strong ground state vibrational modes (negative bands of the component A 3 , Fig. 6) are either positive or negative and resemble the shape of the ground state infrared absorption spectrum (e.g.…”

Photophysical Studies of trans-Bis(phenylethynyldiisopropylamidinato)bis(acetato)dimetal Complexes Involving MM Quadruple Bonds Where M = Mo or W

“…Conformational and vibrational relaxation processes have been previously identified and are distinguishable by transient Raman experiments. 44 Complexes I and II possess strong Raman vibrations associated with the metal-metal and acetylene group stretches, and these experiments should be well suited to address these points.…”