23 June 2000 Ž . Chemical Physics Letters 323 2000 467–473 www.elsevier.nlrlocatercplett Light- and pH-driven electron transfer in the pyranine–methylviologen system C. Prayer a , T.-H. Tran-Thi a, ) , S. Pommeret b , P. d’Oliveira c , P. Meynadier c a DSMr DRECAM, CEA r Saclay, and SPAMr Laboratoire Francis Perrin r Groupe de Photophysique et de Photochimie and CNRS URA 331, 91191 Gif-sur-YÕette Cedex, France b DSMr DRECAM, CEA r Saclay, and SCMr URA 331, 91191 Gif-sur-YÕette Cedex, France c DSMr DRECAM, CEA r Saclay, and SPAMr LUCA, 91191 Gif-sur-YÕette Cedex, France Received 11 January 2000; in final form 4 April 2000 Abstract A face-to-face electrostatic complex is formed in alkaline solution by pairing the trisodium salt of 8-hydroxy-1,3,6- Ž q . Ž 2q pyrenetrisulfonic acid pyranine tsPyOH,3Na , an anionic donor, with the dichloride salt of methyl viologen MV , y . 2Cl , a cationic acceptor. The donor displays dual properties: it can be photoionized or can transfer an electron to the acceptor. It is shown that light absorption by the self-assembled complex leads to the formation of a particularly short-lived Ž . species 3.7 ps assigned to a singlet excited state which relaxes to the ground state via a charge-transfer state. q 2000 Elsevier Science B.V. All rights reserved. 1. Introduction Among the donor–acceptor systems available in the literature, the photophysical properties of self-as- sembled and ionic systems are much less explored, w x in particular in solutions 1–4 where the thermody- namics of formation of the complexes are dependent on many parameters such as the nature of the sol- vent, ionic strength, pH, temperature, and on aggre- wx gation problems 5 . We are interested in model systems where the donor can display dual properties. For instance, it can transfer a proton to the solvent andror an electron to an acceptor. Such transfer processes can be controlled by light absorption and pH variation. Other interesting dual properties are ) Corresponding author. Fax: q 1069-08-87-07; e-mail: tranthi@drecam.cea.fr the ability to transfer an electron to the donor or to be photoionized. In the last case, the resulting elec- tron can either be transferred to the donor moiety or to the solvent and become a solvated electron. This should generate systems in which the competitive Ž . electron-transfer ET processes can be selected with the choice of the excitation wavelength. Such com- petitive processes, H q versus e y transfer and pho- toionization versus e y transfer, frequently occur in biological systems, i.e. when drug molecules are intercalated in ADN and interact with the base units w x 6–8 . To this end, we have begun studying complexes Ž . formed by coupling a donor, pyranine tsPyOH , a trisodium salt of the 8-hydroxy-1,3,6-pyrenetri- sulfonic acid with an acceptor, the dichloride salt of methyl viologen. Pyranine displays the required properties. In acidic or neutral aqueous media, the 0009-2614r00r$ - see front matterq 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2614 00 00542-X