Investigation of non‐Rehm–Weller kinetics in the electron transfer from trivalent phosphorus compounds to singlet excited sensitizers1. (22nd July 2013)

• Record Type: Journal Article
• Authors: Yasui, Shinro; Tsujimoto, Munekazu; Page, Michael I.
• Is Part Of: Journal of physical organic chemistry. Volume 26:Number 12(2013:Dec.)
• Page Start: 1090
• Page End: 1097
• Publication Date: 2013-07-22
• Subjects: Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3170
• Languages: English
• ISSNs: 0894-3230

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Singlet excited states (<sup>1</sup>S<sup>*</sup> and <sup>1</sup>S<sup>+*</sup>) of neutral and monocationic sensitizers, S and S<sup>+</sup>, respectively, were quenched by electron transfer (ET) from a variety of trivalent <named-content id="d219e904" content-type="chemicalTechnology" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">phosphorus compounds</named-content> (Z<sub>3</sub>P). The quenching rate constants <italic>k</italic><sub>q</sub>, which are equal to the rate constants <italic>k</italic><sub>ET</sub> of the ET from Z<sub>3</sub>P to <sup>1</sup>S<sup>*</sup> or <sup>1</sup>S<sup>+*</sup>, were determined by the Stern–Volmer method. The logarithm of <italic>k</italic><sub>ET</sub> was plotted against free‐energy change Δ<italic>G</italic><sup>0</sup> of the ET. The plot deviated upward from the line predicted by the Rehm–Weller (RW) theory in the endothermic region, the deviation being larger in the ET to a neutral acceptor <sup>1</sup>S<sup>*</sup> than in the ET to a cationic acceptor <sup>1</sup>S<sup>+*</sup>. Such a kinetic behavior is in sharp contrast to that observed in the ET from amines (R<sub>3</sub>N), where the ET to either neutral or cationic acceptor takes place according to the RW prediction. The ET from a donor, Z<sub>3</sub>P or R<sub>3</sub>N, to a neutral acceptor <sup>1</sup>S<sup>*</sup> is a charge‐separation type, during which electrostatic attraction between the donor and the acceptor is generated, whereas the ET to a cationic acceptor <sup>1</sup>S<sup>+*</sup> is a charge‐shift type, which results in neither electrostatic attraction nor repulsion. Difference in kinetics–energetics relationship by the type of ET, which is not recognized in the ET from R<sub>3</sub>N donor, becomes "visible" when Z<sub>3</sub>P is used as a donor. Copyright © 2013 John Wiley & Sons, Ltd.</p> </abstract>