title: Spectroscopy of photoinduced charge-transfer reactions between tetrasulfonated aluminium phthalocyanine and methyl viologen.
abstract: Interactions between tetrasulfonated aluminium phthalocyanine (AlPcTS4-) and methyl viologen (Mv2+) have been studied in water and ethanol solutions using several experimental techniques. UV-visible absorption and fluorescence spectroscopies show that ion-pair complexes occur in ethanol, disappearing in more polar environments such as water. Time-resolved fluorescence spectroscopy (picosecond timescale) reveals the existence of several emissive species in ethanol solutions, of which one of the components is attributed to the charge-transfer complex (AlPcTS4-)(Mv2+)2, another to higher-order aggregates and yet another to the isolated AlPcTS4- molecule. The AlPcTS4- emission is quenched by Mv2+, leading to transient diffusion in the fluorescence decay kinetics. On the other hand, the emissive complex has an exponential decay with a relatively long lifetime (above 1 ns). Time-resolved absorption measurements did not reveal the existence of radicals in aqueous solution, even on the picosecond timescale. The spectra reveal the presence of excited singlet state AlPcTS4-, which decays via the triplet excited state back to the ground state.
authors.affiliation: Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 Lisboa, Portugal. cesar.laia@popsrv.ist.utl.pt
authors.forename: César A T
authors.initials: CA
authors.lastname: Laia
authors.forename: Sílvia M B
authors.initials: SM
authors.lastname: Costa
authors.forename: David
authors.initials: D
authors.lastname: Phillips
authors.forename: A W
authors.initials: AW
authors.lastname: Parker