Vibrational Energy Relaxation of S₁ Perylene in Solution

Abstract

Vibrational energy relaxations of S 1 perylene and S 1 12-(3-perylenyl)dodecanoic acid (PD) in 2-methyltetrahydrofuran at room temperature were investigated by using a Franck-Condon analysis of femtosecond time-resolved fluorescence spectra. Vibrational energy relaxation from |2〉, V′ ) 2 level of ν 7 mode, occurs not only via successive route, |2〉 f |1〉 followed by |1〉 f |0〉, but also via direct route, |2〉 f |0〉. The vibrational energy relaxation times were obtained as 2.7 ps for |2〉 f |1〉, 1.8 ps for |1〉 f |0〉, and 700 fs for |2〉 f |0〉 in perylene and 1.9 ps for |2〉 f |1〉, 1.2 ps for |1〉 f |0〉, and 500 fs for |2〉 f |0〉 in PD. An average-matrix-element treatment proposed by Fourmann et al. (Chem. Phys. 1985, 92, 25) was employed to account for these relaxation times in the Fermi's golden rule. Two parameters of the average-matrix element were estimated to be V 0 ) 0.59 cm -1 and 0.46 < R < 0.55 in our analysis, which were in reasonable agreement with Fourmann's analysis, V 0 ) 0.65 cm -1 and R ) 0.3, for fluorescence spectra of perylene in supersonic jet. To discuss the energy flow in the ν 7 mode, transient vibrational temperatures were also calculated at each time. "Intramode" thermal equilibriums in the ν 7 mode both for perylene and for PD are not established while the vibrational temperature is higher than room temperature.

Solvent-assisted intramolecular vibrational energy redistribution of S1 perylene in ketone solvents

“…The time constant τ 3 is also very close to the picoseconds IVR rate that we have found in S 1 perylene in MTHF [12][13]. In a few picoseconds time region, the transient vibrational temperature is still higher than the statistical-limit temperature obtained by assuming that vibrational energy is equi-partitioned over all the vibrational modes of solute [13]. Therefore, there is a possibility that τ 3 reflects the SA-IVR process rather than VET.…”

“…V 0 and α have been determined as V 0 = 0.59 cm -1 and 0.46 < α < 0.5 for perylene in MTHF solution 9 [13]. We estimated the number of the solvent molecules, N l=2,3 , by eqs.…”

“…2800 cm -1 of S 1 perylene and S 1 12-(3-perylenyl)dodecanoic acid (PD) in 2-methyltetrahydrofuran (MTHF) with a femtosecond fluorescence up-conversion method [12][13]. The VER rate of PD is faster than that of perylene; therefore we concluded that the observed VER process includes the contribution from IVR, because the IVR rate is generally accelerated by the increase of the density of vibrational states of molecule.…”

“…Many experimental and theoretical studies have been reported on VER in the last decade [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. that IVR is further classified into two processes in solutions; the fast IVR that takes place in tens of femtoseconds to sub picoseconds time scales and the slow IVR in a few picoseconds time scale [5][6][7][8].…”

Charge Transfer Assisted by Collective Hydrogen‐Bonding Dynamics

“…The maxima of the broad absorption bands are located near 470 nm, which differs substantially from that in the parent molecule perylene (around 430 nm). [30] Although there is no perceivable spectral shift when the solvent is changed from ACN to MeOH, a systematic change in the red tail of the absorption with the increase of the MeOH concentration is observed. This change indicates the formation of a H-bonded complex between FPe and MeOH; the probability of dimer formation is very low as the concentration FPe is very low Scheme 1.…”