UNIGE document Scientific Article
previous document  unige:34401  next document
add to browser collection
Title

Excitation wavelength dependence of the charge separation pathways in tetraporphyrin-naphthalene diimide pentads

Authors
Kelson, Melissa M. A.
Bhosale, Sheshanath V.
Published in Physical Chemistry Chemical Physics. 2014, vol. 16, no. 11, p. 5188
Abstract The excited-state dynamics of two multichromophoric arrays composed of a naphthalene diimide centre and four zinc or free-base porphyrins substituted on the naphthalene core via aniline bridges has been investigated using a combination of stationary and ultrafast spectroscopies. These pentads act as efficient antennae as they absorb over the whole visible region, with a band around 700 nm, associated with a transition to the S1 state delocalised over the whole arrays, and bands at higher energy due to transitions centred on the porphyrins. In non-polar solvents, population of these porphyrin states is followed by sub-picosecond internal conversion to the S1 state. The existence of a charge-separated state located above the S1 state could enhance this process. The decay of the S1 state is dominated by non-radiative deactivation on the 100 ps timescale, most probably favoured by the small S1-S0 energy gap and the very high density of vibrational states of these very large chromophores. In polar solvents, the charge-separated state lies just below the S1 state. It can be populated within a few picoseconds by a thermally-activated hole transfer from the S1 state as well as via sub-picosecond non-equilibrium electron transfer from vibrationally hot porphyrin excited states. Because of the small energy gap between the charge-separated state and the ground state, charge recombination is almost barrierless and occurs within a few picoseconds. Despite their very different driving forces, charge separation and recombination occur on similar timescales. This is explained by the electronic coupling that differs considerably for both processes.
Identifiers
Full text
Article (Published version) (3.1 MB) - document accessible for UNIGE members only Limited access to UNIGE
Other version: http://xlink.rsc.org/?DOI=c3cp54871f
Structures
Research group Groupe Vauthey
Citation
(ISO format)
VILLAMAINA, Diego et al. Excitation wavelength dependence of the charge separation pathways in tetraporphyrin-naphthalene diimide pentads. In: Physical Chemistry Chemical Physics, 2014, vol. 16, n° 11, p. 5188. https://archive-ouverte.unige.ch/unige:34401

233 hits

0 download

Update

Deposited on : 2014-02-21

Export document
Format :
Citation style :