Encapsulation of Luminescent Homoleptic [Ru(dpp)₃]²⁺‐Type Chromophores within an Amphiphilic Dendritic Environment

Abstract

A new series of homoleptic metallodendrimers has been synthesized through ruthenium-metal complexation by dendritically modified bathophenanthroline ligands. The presence of hydrophilic oligo(ethylene glycol) groups on the surface of the monodisperse metal complexes enabled the solubilization of all of the fractal species in a wide range of solvents, including water. The specific properties of all of these compounds have been systematically investigated by using photophysical techniques as a function of the generation number. Accordingly, the encapsulation of the highly luminescent [Ru(dpp)(3)](2+)-type (dpp=4,7-diphenyl-1,10-phenanthroline) core unit within a dendritic microenvironment creates a powerful means to shield the center from dioxygen quenching. This shielding effect, as exerted on the phosphorescent ruthenium-derived center, is reflected by enhanced emission intensities and extended excited-state lifetimes that are close to the highest values reported so far, even in an air-equilibrated aqueous medium. Interestingly, when inspecting the largest dendritic assembly, that is, the third-generation assembly, significant drops in emission quantum yields and lifetimes are observed. This anomalous behavior has been attributed to the folding of the branches towards the luminescent core.

Easily prepared ruthenium-complex nanomicelle probes for two-photon quantitative imaging of oxygen in aqueous media

“…2,19 To overcome this problem, hydrophobic dyes are usually PEGylated which involves the attachment of hydrophilic functional groups and/or dendrimers to enhance water-solubility. 2,20,21 The Oxyphor family of probes (Oxyphor-R2, -G2, -R4, and -G4) is a good example of changing the hydrophobicity of palladium-porphyrins by adding hydrophilic dendrimers. [22][23][24] However, the Oxyphor probes lack two-photon cross-sections and thus they cannot be used in multiphoton microscopy 25,26 for high-resolution and depth-resolved bioimaging.…”

Biocompatible Ir(III) Complexes as Oxygen Sensors for Phosphorescence Lifetime Imaging

“…It is also worth noting that lifetime sensitivity of these complexes is relatively low that is typical for transition metal chromophores (e.g., iridium [ 27 ] and ruthenium [ 53 ] emitters) in aqueous media. Nevertheless, the lifetime interval of ca.…”

Light-sensitive ruthenium complex-loaded cross-linked polymeric nanoassemblies for the treatment of cancer

“…Based on agarose gel electrophoresis experiments, it is once again apparent that the release rate of Ru complexes is inversely proportional to complex hydrophobicity and that under these experimental conditions PEG-ASP CNAs can shield Ru complex-DNA interactions, including those mediated by the sensitization of 1 O 2 , as oxygen may not readily penetrate into the CNA, preventing generation of 1 O 2 . 19 …”