Aspects of artificial photosynthesis. Photosensitized electron transfer and charge separation in cationic surfactant vesicles

Journal Article · Wed Feb 27 00:00:00 EST 1980 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00525a001· OSTI ID:5279575

Infelta, P P; Graetzel, M; Fendler, J H

Electron transfer and charge separation have been investigated in cationic dioctadecyldimethylammonium chloride (DODAC) vesicles by laser spectroscopy. h-Methylphenothiazine (MPTH) and its long-chain analogue, N-dodecylphenothiazine (DPTH), were used as electron donors, while a surfactant derivative of tris(2,2'-bipyridine)ruthenium perchlorate, RuC/sub 18/(bpy)/sub 3//sup 2 +/, acted as the photoactive electron acceptor, DODAC vesicles organized these donor and acceptor molecules. RuC/sub 18/(bpy)/sub 3//sup 2 +/ molecules were anchored onto the surface of the vesicles, while MPTH molecules were distributed among the hydrophobic bilayers of the vesicles. The metal to ligand charge transfer excited state of the ruthenium complex, RuC/sub 18/(bpy)/sub 3//sup 2 +/*, readily accepted an electron from MPTH to give MPTH/sup +/ and RuC/sub 18/(bpy)/sub 3//sup +/. First, there is a rapid geminate recombination at the very site of the generation of the cation radical. Second, some of the MPTH/sup +/. Escapes into the vesicle entrapped water pools and, owing to spatial confinement, the combination occurs at the inner surface of the vesicles. Finally, a part of MPTH/sup +/. Escapes into the bulk aqueous solution where it survives for extended periods (>>1 ms). MPTH and NaCl affect the outer surface charge density of the vesicles. The amounts of MPTH/sup +/. produced and that expelled into the bulk aqueous solution were maximized in the presence of 1.0 x 10/sup -3/ M NaCl. Under this condition there was still a sufficient electrostatic repulsion between MPTH/sup +/. and the charged surface of the vesicles to slow down considerably the undesirable charge recombination reactions. Carrying out the electron transfer using DPTH resulted only in short-lived DPTH/sup +/. in low concentrations. The long hydrocarbon chain on this molecule prevented the expulsion of this cation radical from the vesicle. Relevance of this study to light-induced photochemical energy conversion is discussed.

• Research Organization: Ecole Polytechnique Federale, Lausanne, Switzerland
• OSTI ID: 5279575
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 102:5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ENERGY CONVERSION
PHOTOCHEMICAL REACTIONS
SURFACTANTS
ELECTRON TRANSFER
BINDING ENERGY
CATIONS
ELECTRONS
LASER SPECTROSCOPY
LIGANDS
ORGANIC CHLORINE COMPOUNDS
PHOTOSYNTHESIS
RUTHENIUM COMPLEXES
RUTHENIUM COMPOUNDS
VALENCE
CHARGED PARTICLES
CHEMICAL REACTIONS
COMPLEXES
CONVERSION
ELEMENTARY PARTICLES
ENERGY
FERMIONS
IONS
LEPTONS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
400500* - Photochemistry
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)