title: Preparation and photochemistry of single wall carbon nanotubes having covalently anchored viologen units.
abstract: An asymmetrically substituted viologen (V) has been covalently anchored to single wall carbon nanotube (SWNT) through an ester linkage by reacting chlorinated purified SWNT with N-methyl-N'-(6-hydroxyhexyl)-4,4'-bipyridine. Spectroscopic evidence for the covalent bond of viologen in V-SWNT comes from the chemical shift of the -CH2-O-CO- methylene group in 1H NMR and from the variations of the 1590 and 1380 cm(-1) bands in the Raman spectrum of the V-SWNT with respect to SWNT. The fact that the estimated quenching constant of the SWNT emission by viologen is about 2 orders of magnitude higher than the diffusion coefficient indicates the occurrence of a static quenching arising from the formation of a nonemissive viologen-SWNT complex. Laser flash photolysis shows the formation of viologen radical cation upon direct excitation of V-SWNT. The viologen moiety of V-SWNT is able to form a charge-transfer complex with 2,6-dimethoxynaphthalene (DMN) as evidenced by optical spectroscopy and, upon selective photoexcitation in the charge-transfer band, this V-DMN complex anchored to SWNT gives rise to the corresponding charge separated state decaying in the submillisecond time scales.
authors.affiliation: Instituto de Tecnología Química CSIC-UPV and Departamento de Química UPV, Avda de los Naranjos s/n, 46022 Valencia, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Alvaro
authors.forename: Carmela
authors.initials: C
authors.lastname: Aprile
authors.forename: Pedro
authors.initials: P
authors.lastname: Atienzar
authors.forename: Hermenegildo
authors.initials: H
authors.lastname: Garcia