A Convergent Approach for the Generation of Dendrimers Containing the [Ru3O(CH3COO)6] Electroactive Core (original) (raw)
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Journal of the American Chemical Society, 1999
We report the synthesis of six new dendrimers built around a [Ru(bpy) 3 ] 2+ -type core (bpy ) 2,2′bipyridine) and bearing up to 24 4′-tert-butylphenyloxy or 48 benzyl units in the periphery. The metallodendrimers were obtained by complexation of ruthenium trichloride or Ru(bpy) 2 Cl 2 with bipyridine ligands carrying dendritic wedges in the 4,4′-positions. The absorption spectra and luminescence properties (spectra and lifetimes at 77 and 298 K; quantum yields at 298 K) of the six novel compounds are reported. All of them show the characteristic luminescence of the [Ru(bpy) 3 ] 2+ -type core unit. The dendritic branches protect the luminescent excited state of the core by dioxygen quenching. For the three compounds containing the 4′-tert-butylphenyloxy peripheral units, the electrochemical behavior and the excited-state quenching via electron transfer were also studied. The electrochemical experiments have evidenced an oxidation and three reduction one-electron processes centered in the [Ru(bpy) 3 ] 2+ -type core and two multielectron oxidation processes involving the dioxybenzeneand oxybenzene-type units of the dendritic branches. The core of the largest dendrimer shows an electrochemical behavior typical of encapsulated electroactive units. The reaction of the luminescent excited state of the [Ru-(bpy) 3 ] 2+ -type core with three electron-transfer quenchers (namely, methyl viologen dication, tetrathiafulvalene, and anthraquinone-2,6-disulfonate anion) was found to take place by a dynamic mechanism in all cases. The quenching rate constants, obtained by Stern-Volmer kinetic analysis, are compared with those found for the simple [Ru(bpy) 3 ] 2+ complex. The results show that, for each quencher, the value of the rate constant decreases with increasing number and size of the dendritic branches. For the second-generation dendrimer containing 24 4′-tert-butylphenyloxy units at the periphery, the rate constant of the reaction with methyl viologen is more than 1 order of magnitude smaller than that of the "naked" [Ru(bpy) 3 ] 2+ complex. All the experiments were performed in acetonitrile solution, except for luminescence experiments at 77 K where butyronitrile was used.
Organometallic chemistry at the nanoscale. Dendrimers for redox processes and catalysis
Pure and Applied Chemistry, 2000
An overview of the metal-mediated synthesis and use of nanosized metallodendrimers is given with emphasis on electron-transfer processes (molecular batteries consisting in dendrimers decorated with a large number of equivalent redox-active centers) and catalytic reactions (electron-transfer-chain catalytic synthesis of dendrimers decorated with ruthenium carbonyl clusters, redox catalysis of nitrate and nitrite electroreduction in water by star-shape hexanuclear catalysts).
Analytical and Bioanalytical Chemistry, 2016
Electrogenerated chemiluminescence (ECL) reactions between tris(2,2′-bipyridine)ruthenium(II) and PAMAM dendrimers of the full (G1.0) and half (G1.5) generations were carried out in an aqueous medium at pH 6.1 and 10.0. In the absence of 5-fluoro-1H,3H-pyrimidine-2,4-dione (5-fluorouracil, 5-Fu) (coreactant effect study), the ECL efficiency trends as a function of [G1.0] and [G1.5] at pH 6.1 and 10.0 revealed that PAMAM dendrimers are about 100 (G1.5, pH 6.1), 60 (G1.5, pH 10.0), 26 (G1.0, pH 10.0) and 13 (G1.0, pH 6.1) times more efficient as ECL coreactants than oxalate anion is. Moreover, ECL reactions were done in the presence of several solutions of 5-Fu at a fixed concentration of the G1.0 and G1.5 dendrimers at pH 6.1 and 10.0 (binding study). The ECL efficiency trends as a function of [5-Fu] highlighted a dendrimer/5-Fu binding. Therefore, one of the most remarkable and novel findings of this work is the potential of PAMAM dendrimers to be used as both sensors and biosensors in an aqueous medium in the presence of a suitable sensitizer. Redox potentials of the [Ru(bpy) 3 ] 3+/2+ couple were also determined in the absence and presence of 5-Fu at both pHs. In the absence of 5-Fu the positive or negative shift of redox potentials showed the influence of the repulsive or attractive electrostatic long-range and short-range interactions between the charged dendrimer surface and the oxidized and reduced forms of the couple. In the presence of 5-Fu the trends of redox potentials highlighted the existence of a charged dendrimer/5-Fu species.
Chemical Physics Letters, 2004
The kinetics of the electron transfer reaction between [Ru(NH 3) 5 pz] 2+ (pz = pyrazine) and [Co(C 2 O 4) 3 ] 3À ðC 2 O 2À 4 ¼ oxalate anionÞ was studied in solutions of the SB1.5G dendrimer at different concentrations of a supporting electrolyte (NaCl) and in solutions of the SB4.5G dendrimer. The results are interpreted on the basis of a modified pseudophase model, which takes into account the anti-cooperative character of the cationic reactant binding to the dendrimers. With regard to the binding characteristics of small cationic ligands, and their influences on the kinetics of reactions in which these small ions participate, the conclusion was that dendrimers and DNA behave similarly.
Organometallics, 2014
Four firstand second-generation heterometallic ferrocenyl derived p-cymene-Ru(II) metallodendrimers, of general formula [DAB-PPI{(η 6 -p-cymene)Ru((C 7 H 5 NO)-κ 2 -N,O)PTA(5-ferrocenylvinyl)} n ][PF 6 ] n and [DAB-PPI{(η 6 -pcymene)Ru((C 6 H 5 N 2 )-κ 2 -N,N)Cl(5-ferrocenylvinyl)} n ][PF 6 ] n (where n = 4 (G 1 ), 8 (G 2 ), DAB = 1,4-diaminobutane, PPI = p o l y ( p r o p y l e n e i m i n e ) , P T A = 1 , 3 , 5 -t r i a z a -7phosphatricyclo[3.3.1.1]decane) have been synthesized. All complexes have been characterized using analytical (i.e., HR-ESI mass spectrometry, HPLC, elemental analysis, and cyclic voltammetry) and spectroscopic (i.e., 1 H and 13 C{ 1 H} NMR and infrared) methods. Electrochemical studies reveal that the N,O-p-cymene-Ru(II)-PTA complexes result in two irreversible redox processes (oxidation of the Fe(II) and Ru(II) centers), while the N,N-p-cymene-Ru(II) complexes display one reversible wave (Fe(II)/Fe(III) couple). Heterometallic model complexes have been prepared, and for one of the complexes, its molecular structure has been determined by single-crystal X-ray crystallography. In vitro antiproliferation activity of the dendritic ligands and their complexes were evaluated against A2780 and A2780cisR human ovarian cancer lines, the SISO human cervix cancer line, the LCLC-103H human lung cancer line, and the 5637 human bladder cancer line. Nine of the twelve compounds slowed the growth of the ovarian cancer cell lines by more than 50% at equi-iron concentrations of 5 μM.
Chemistry - A European Journal, 2002
A series of dendritic cations 1 ± 4 containing Ru 2 S 3 or Rh 2 S 3 units, either in the core or in the dendrons, has been synthesized and characterized. The X-ray crystal structure analysis of 2-Cl shows a trigonal bipyramidal Rh 2 S 3 core with propeller-like para-hydroxyphenyl substituents at the sulfur atoms. Reac-tion of the peripheral OH groups with diphenylphosphino benzoic acid results in the formation of phosphine-functionalized dendritic cations 5 ± 8. The ruthe-nium-containing cation 5, with three PPh 2 functions at the periphery, acts as ligand for rhodium(i) and enhances significantly the catalytic activity of [{Rh(CO) 2 Cl} 2 ] for the carbonylation of methanol.
Reviews in Molecular Biotechnology, 2002
Dendrimers are well-defined hyperbranched macromolecules with characteristic globular structures for the larger systems. The recent impressive strides in synthetic procedures increased the accessibility of functionalized dendrimers at a practicable scale, resulting in a rapid development of dendrimer chemistry. Dendrimers have inspired many chemists to develop new materials and several applications have been explored, catalysis being one of them. Ž. The position of the catalytic site s as well as the spatial separation of the catalysts within the dendritic framework is of crucial importance. Dendrimers that are functionalized with transition metals in the core can potentially mimic properties of enzymes, their efficient natural counterparts, whereas the surface-functionalized systems have been proposed to fill the gap between homogeneous and heterogeneous catalysis. We prepared both core-and peripheryfunctionalized dendritic catalysts that are sufficiently large to enable separation by modern nanofiltration techniques. Here we review our recent findings using these promising novel transition metal-functionalized dendrimers as catalysts in several reactions. We will discuss some of the consequences of the architecturally different systems that have been studied and will elaborate on a novel non-covalent strategy of dendrimer functionalization.
A multichromophoric dendrimer: from synthesis to energy up-conversion in a rigid matrix
Chemical Communications, 2011
A dendrimer with a [Ru(bpy) 3 ] 2+ (bpy = 2,2 0 -bipyridine) complex as a core and four diphenylanthracene units at the periphery was prepared from a scaffold based on a bipyridyl ligand bearing four terminal alkyne groups. Upon green light excitation, the dendrimer shows blue luminescence even in a rigid matrix at 77 K thanks to the dendritic multichromophoric structure.
Journal of Inorganic and Organometallic Polymers and Materials, 2007
This micro-review shows how a simple but powerful organometallic C-H activation could be made very useful for the construction of a large variety of stars, dendritic cores, dendrons and dendrimers of variable sizes including giant dendrimers and gold-nanoparticle-cored dendrimers. The synthesis of ferrocenyl-terminated dendrimers was then achieved by reactions of chlorocarbonylferrocene with polyamino dendrimers, ferrocenylsilylation of polyolefin dendrons and dendrimers and ''click'' reactions of ferrocenyl acetylene with azidoterminated dendrimers. The functions of these metallodendrimers include molecular electronics (molecular batteries), molecular redox recognition and sensing and catalysis using dendritic stabilization of nanoparticle catalysts.