Hydrophilic oxybathophenanthroline ligands: synthesis and copper(ii) complexation

Luelf

Winkler

et al. 2012

Chemistry A European J

Self Cite

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.

Section: Resultsmentioning

confidence: 99%

“…General : All reagents were used as purchased from commercial sources without further purification. Dendritic ligands P1 – P3 were prepared according to a literature procedure 12h. Solvents were dried by using standard techniques prior to use.…”

Section: Methodsmentioning

confidence: 99%

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

Luelf

Winkler

et al. 2012

Chemistry A European J

Self Cite

“…On the other hand, dendrons carrying triethylene glycol monomethyl ether end groups and a benzylic bromide function at the centre were obtained following a literature procedure [8][9][10][11]. Subjection to a reaction with sodium azide then readily formed the corresponding azide derivatives 4-6 in quantitative yields [9].…”

Section: Synthesismentioning

confidence: 99%

“…Dendritic azides 4-6 were prepared according to a procedure as previously described in the literature [9,11]. Solvents were dried using standard techniques prior to use.…”

Section: Experimental Generalmentioning

confidence: 99%

Amphiphilic zinc phthalocyanine dendrimers by the Click Chemistry approach

J. Porphyrins Phthalocyanines

Torres

2011

Self Cite

A series of new zinc phthalocyanine dendrimers with an increasing branched shell of oligoethylene glycol end groups has been synthesized. Owing to the presence of these hydrophilic termini at the dendrimer surface, all compounds are highly soluble in a wide range of solvents including water. The monodispersity of the amphiphilic dendrimers has been unambiguously evidenced by both NMR and MS techniques. UV-vis experiments point out that the tendency of the central phthalocyanine chromophore to aggregate in polar protic solvents is not significantly reduced regardless of the dendritic shell surrounding the macrocyclic chromophore.

“…Accordingly, first to third Fre´chet-type dendrons with terminal oligoethylene glycol chains have been obtained via the well-established protocol as reported in the literature. 20,21 The first generation intermediate 1 bearing a benzylic alcohol function at the focal point was then coupled to a 3,5-disubstituted pyridine derivative using two different strategies. Initial attempts were based thereby on the transformation of the diacid into the corresponding diacid dichloride under the use of thionyl chloride and a catalytic amount of dimethylformamide and subsequent reaction with 1 to give diester 5 in 68% yield after purification by chromatography.…”

Section: Synthesismentioning

confidence: 99%

Microenvironment-switchable singlet oxygen generation by axially-coordinated hydrophilic ruthenium phthalocyanine dendrimers

Phys. Chem. Chem. Phys.

Setaro

Ragàs

et al. 2011

Self Cite

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.