Using vibrational transient absorption spectroscopy, we investigate how the position of the electron acceptor (A) relative to the donor (D) affects the localisation of the electronic excitation in A-D-A dyes synthesised in the group of T.J.J. Müller (HHU Düsseldorf).
The figure depicts the transient spectra in the -C≡N stretching region of the relaxed S1 state in solvents of increasing polarity. The single positive band in cyclohexane (CHX) points to an even distribution of the exciton on both D-A branches. The frequency shift relative to the ground state bleach (blue arrow) increases from meta to para and to ortho positions, reflecting an increasing charge transfer character of the S1 state. The splitting of the band when going to DMSO results from excited-state symmetry breaking, with the extent of asymmetry increasing with the frequency splitting of the two C≡N stretching bands (red arrow). Consequently, the relative position of the acceptor has a signifiant impact on the localisation of the exciton.
| FOR MORE INFORMATION | ||
  |
||
Contact:
Eric Vauthey
Physical Chemistry Department - Sciences II - University of Geneva
30, Quai Ernest Ansermet - CH-1211 Geneva 4 (Switzerland)
© All rights reserved by Eric Vauthey and the University of Geneva
Design and code by Guillaume Duvanel