title: Microenvironment-switchable singlet oxygen generation by axially-coordinated hydrophilic ruthenium phthalocyanine dendrimers.
abstract: A series of new metallodendrimers built around a ruthenium phthalocyanine core has been prepared. Employing a convergent synthetic strategy, pyridine-containing ligands were prepared and then assembled onto the ruthenium phthalocyanine through axial ligand coordination. The growing shell of oligoethylene glycol chains surrounding the lipophilic core allows solubilisation in water. Photophysical studies show that all the metallodendrimers are strongly phosphorescent and the deactivation pathway of their triplet state depends on the medium in which the compounds are dissolved. On one hand, quenching of the triplet state by the dendritic shell is observed and found to be substantially enhanced in aqueous media. On the other, the dendrimer shields the phthalocyanine from oxygen. This notwithstanding, the phthalocyanines are able to generate singlet oxygen in less polar environments such as in CHCl(3) or THF solution, while in water the generation of singlet oxygen is almost completely switched off.
authors.affiliation: Departamento de Química Orgánica, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Uwe
authors.initials: U
authors.lastname: Hahn
authors.forename: Francesca
authors.initials: F
authors.lastname: Setaro
authors.forename: Xavier
authors.initials: X
authors.lastname: Ragàs
authors.forename: Angus
authors.initials: A
authors.lastname: Gray-Weale
authors.forename: Santi
authors.initials: S
authors.lastname: Nonell
authors.forename: Tomas
authors.initials: T
authors.lastname: Torres