Ultrafast Spectroscopic Investigation of the Charge Recombination Dynamics of Ion Pairs Formed upon Highly Exergonic Bimolecular Electron-Transfer Quenching: Looking for the Normal Region

Pages, Stéphane; Lang, Bernhard Felix; Vauthey, Eric

doi:10.1021/jp036796g

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Title		Ultrafast Spectroscopic Investigation of the Charge Recombination Dynamics of Ion Pairs Formed upon Highly Exergonic Bimolecular Electron-Transfer Quenching: Looking for the Normal Region
Authors		Pages, Stéphane Lang, Bernhard Felix Vauthey, Eric
Published in		Journal of Physical Chemistry. A. 2004, vol. 108, no. 4, p. 549-555
Abstract		The charge recombination dynamics of the ion pairs formed upon electron-transfer quenching of perylene by tetracyanoethylene in acetonitrile has been investigated using ultrafast fluorescence upconversion, transient absorption, and transient grating techniques. For this donor/acceptor pair, charge separation is highly exergonic (ΔG[CS]= −2.2 eV), but charge recombination is weakly exergonic (ΔG[CR] = −0.6 eV). It was found that for more than 90% of the ion pair population, charge recombination is ultrafast and occurs in less than 10 ps. This decay component could not be observed in a previous investigation with a lower time resolution. The results indicate that the primary quenching product is a contact ion pair and not a solvent-separated ion pair as generally assumed for highly exergonic electron-transfer quenching processes. A possible explanation for this apparent divergence is that the contact ion pair is initially formed in an electronic excited state. Only a very minor fraction of the ion pair population undergoes the slow charge recombination predicted by Marcus theory for weakly exergonic charge-transfer processes (normal region).
Identifiers		DOI: 10.1021/jp036796g
Full text		Other version: http://pubs.acs.org/cgi-bin/article.cgi/jpcafh/2004/108/i04/pdf/jp036796g.pdf
Structures		Faculté des sciences / Section de chimie et biochimie / Département de chimie physique
Research group		Groupe Vauthey
Citation (ISO format)		PAGES, Stéphane, LANG, Bernhard Felix, VAUTHEY, Eric. Ultrafast Spectroscopic Investigation of the Charge Recombination Dynamics of Ion Pairs Formed upon Highly Exergonic Bimolecular Electron-Transfer Quenching: Looking for the Normal Region. In: Journal of Physical Chemistry. A, 2004, vol. 108, n° 4, p. 549-555. doi: 10.1021/jp036796g https://archive-ouverte.unige.ch/unige:3517