Fluorescence Quenching in Electron-Donating Solvents. 1. Influence of the Solute−Solvent Interactions on the Dynamics

Abstract

The electron transfer (ET) quenching dynamics of excited perylene (Pe), cyanoperylene (PeCN), methanolperylene (PeOH), and methylperylene (PeMe) in N,N-dimethylaniline (DMA) has been investigated using ultrafast fluorescence up-conversion. Measurements of the rotational dynamics of PeCN and PeMe in nonpolar and polar inert solvents using optically heterodyned polarization spectroscopy are also presented. The fluorescence decay in DMA is strongly nonexponential and about 10 times faster with PeCN than with the other electron acceptors. The quenching dynamics has been analyzed with a model distinguishing three types of donor molecules surrounding the acceptor: those with optimal orientation for ET and those requiring orientational or translational diffusion prior to ET. According to this model, which can account for the whole fluorescence decay, the faster quenching dynamics of PeCN is not due to a larger ET rate constant, but to a larger number of donor molecules, typically three to four, with an optimal orientation. This is explained by the effect of dipole-dipole interaction between PeCN and the donor molecules, which favors mutual orientations with a large electronic coupling. With the other acceptors, this interaction is either not present or does not lead to ET active geometries. The occurrence of this interaction is substantiated by the rotational dynamics measurements.

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

“…In Figure 2 fs) for fluorescence profiles of perylene in toluene, however, these author avoided elaborate discussion because of complicated characteristics [24]. Their observation in subpicoseconds region agrees with our experimental data.…”

Investigation of the Influence of Solute−Solvent Interactions on the Vibrational Energy Relaxation Dynamics of Large Molecules in Liquids

“…A calculated dipole moment of 4.2 D has been reported for PeCN in the ground state. 40 The insertion of this value and the slope of the solvatochromic plot in the usual equation for the fluorescence solvatochromism due to dipoledipole interaction 39 yield an electric dipole moment of about 6 D for PeCN in the S 1 state. Figure 1B shows the fluorescence spectrum of Pe in the gas phase recorded at different temperatures and normalized to the same area.…”

Ultrafast Photoinduced Charge Separation in Naphthalene Diimide Based Multichromophoric Systems in Liquid Solutions and in a Lipid Membrane

“…This very rapid quenching can be accounted for by the high quencher concentration, 4 M DMA in MeOH corresponding to a 1:1 (v/ v) DMA/MeOH mixture, as subpicosecond time constants have been reported for the quenching of several excited chromophores in pure DMA. [58][59][60] As a consequence, the transient spectra should be dominated by the absorption of the quenching product, namely, the radical anion R1 •-and the radical cation DMA •+ , as well as by the bleach of the S 0 -S 1 absorption. As DMA •+ is known to only exhibit a weak absorption band around 475 nm, 61 all the positive TA features come from R1 •-, whereas the negative signal at 532 nm originates from the bleach of the ground-state absorption.…”