Heteroatom-Based Dendrimers

Frey, Holger; Lach, Christian; Lorenz, K.

doi:10.1002/(sici)1521-4095(199803)10:4<279::aid-adma279>3.3.co;2-6

Cited by 37 publications

(59 citation statements)

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“…While linear or branched polymers cannot define their structures and coordination in one limited form, macromolecular ligands based on the dendrimers can be used as a template for the precise macromolecule-metal hybridization because they have a single molecular weight and a spherelike structure. [21][22][23][24] In general, dendrimers bearing rigid -conjugating backbones are known to have a dense shell and a sparse core. 25,26 The nano-space around the core unit is utilized as a molecular-capsule for capturing metal ions, [27][28][29][30][31][32][33] clusters, [34][35][36][37][38][39][40][41][42] or other guest molecules.…”

Section: Metallo-dendrimer Complexesmentioning

confidence: 99%

Dendrimer Complexes Based on Fine-Controlled Metal Assembling

Yamamoto¹,

Imaoka²

2006

Bulletin of the Chemical Society of Japan

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A series of novel dendrimers composed of dendritic phenylazomethines (DPAs) were synthesized with several types of functional cores. The metal assembling to the DPAs is stepwise by the layers, therefore, they can be used as a scaffold for the precise hybridization between metal ions and organic macromolecules. Because of uniform structure of the dendrimer, there is no structural dispersion in the macromolecule-metal hybrid of the DPAs. Also, the number of metal ions loaded in one dendrimer should have no statistical distribution in principle due to the precise metal assembling. A rigid -conjugating backbone structure contributes not only to the stepwise metal assembly, but also to the solid-state stability under high temperature. Development of this property without any reduction in solubility in organic media enabled the easy preparation of homogeneous amorphous films in which the metal and macromolecule are precisely hybridized. As a result, the thin solid of the metal-assembling dendrimer acts as an excellent organic semiconductor in the hole-transport layer of a light-emitting diode. Metal-assembling DPAs also enhance the electron-transfer reaction as a protein-like catalyst. The DPA having a cobalt porphyrin core-could catalyze the CO 2 reduction at an applied overpotential 1.1 V lower than that needed for the catalysis by a model compound of the porphyrin core (CoTPP). Reversible encapsulation/release of multiple irons is also demonstrated as a mimic of the iron storage protein (Ferritin). The switching between these two coordinating states can be completely controlled by the redox states of the iron (Fe II / Fe III ). The finding of these unique dendritic ligands will afford new insight into molecular design for finely controlled macromolecule-metal hybrid materials. Metallo-Dendrimer ComplexesMacromolecule-metal complexes 1 are defined as molecularlevel hybrids built up with metal complexes and organic polymers. They have been noted in evolution of novel functions based on synergetic effect between the functionality of each part (metal and polymer). For example, applications of these materials for fixation of catalysts, 2 functional modified electrodes based on electron [3][4][5] /ion 6 conductivity, electron-spin control, 7 and amplification of photoelectron conjugating properties 8 demonstrate outstanding enhancement. Most of them are induced by (1) supporter effect, (2) concentration/dilution effect, (3) environmental effect, (4) conformational effect, and (5) cooperative/concerted effect by micro domains in the polymers. For maximum use of these domains, a general methodology that can handle the higher-order structure of the hybrids is strongly required. All the molecular, hybrid, and higher-order structures of the conventional macromolecule-metal complexes are however dispersed with statistical distribution, and impossible to fix themselves into one limited form. Now many research interest moved to the next stage focusing on the control of higher-order structures using self-assembling approach based...

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Section: Metallo-dendrimer Complexesmentioning

confidence: 99%

Dendrimer Complexes Based on Fine-Controlled Metal Assembling

Yamamoto¹,

Imaoka²

2006

Bulletin of the Chemical Society of Japan

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“…A vast range of other applications for surface-confined dendrimers have been reported or can be imagined. Many are summarized in recent review papers [3][4][5]53].…”

Section: Dendrimers As Building Blocks For Surface Modificationmentioning

confidence: 99%

“…This is particularly true in light of the high number of metal ions that can be complexed to a single dendrimer and (in some cases) their well-defined position in the dendrimer. For example, there has been much recent speculation that these materials will be useful for catalysis [3,4,53,[59][60][61][62]. Other applications that take advantage of the photonic, electronic, and magnetic properties of these interesting materials are also envisioned [53,61,62].…”

Section: Dendrimer-encapsulated Metal Ions Metals and Semiconductorsmentioning

confidence: 99%

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Dendrimer-Encapsulated Metals and Semiconductors: Synthesis, Characterization, and Applications

Crooks

Lemon

Sun

et al. 2000

Topics in Current Chemistry

209

162

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This chapter describes composite materials composed of dendrimers and metals or semiconductors. Three types of dendrimer/metal-ion composites are discussed: dendrimers containing structural metal ions, nonstructural exterior metal ions, and nonstructural interior metal ions. Nonstructural interior metal ions can be reduced to yield dendrimer-encapsulated metal and semiconductor nanoparticles. These materials are the principal focus of this chapter. Poly(amidoamine) (PAMAM) and poly(propylene imine) dendrimers, which are the two commercially available families of dendrimers, are in many cases monodisperse in size. Accordingly, they have a generation-dependent number of interior tertiary amines. These are able to complex a range of metal ions including Cu 2+ , Pd 2+ , and Pt 2+ . The maximum number of metal ions that can be sorbed within the dendrimer interior depends on the metal ion, the dendrimer type, and the dendrimer generation. For example, a generation six PAMAM dendrimer can contain up to 64 Cu 2+ ions. Nonstructural interior ions can be chemically reduced to yield dendrimer-encapsulated metal nanoparticles. Because each dendrimer contains a specific number of ions, the resulting metal nanoparticles are in many cases of nearly monodisperse size. Nanoparticles within dendrimers are stabilized by the dendrimer framework; that is, the dendrimer first acts as a molecular template to prepare the metal nanoparticles and then as a stabilizer to prevent agglomeration. These composites are useful for a range of catalytic applications including hydrogenations and Heck chemistry. The unique properties of the interior dendrimer microenvironment can result in formation of products not observed in the absence of the dendrimer. Moreover the exterior dendrimer branches act as a selective gate that controls access to the interior nanoparticle, which results in selective catalysis. In addition to single-metal nanoparticles, it is also possible to prepare bimetallic nanoclusters and dendrimer-encapsulated semiconductor nanoparticles, such as CdS, using this same general approach.

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“…Dendrimer are macromolecules with repetitive branches attached to a central core or focal point [1,2]. Three parameters (b,Z,g) characterize the dendrimer lattice model in Fig.1: the number of branches b attached to the focal point, the connectivity Z of a site and the number of generations g. Many natural systems are dendrimers and molecular engineering can produce custom dendrimers with constituents that range from carbon-based molecules [3] to organo-metallic compounds [4,5]. Potential applications include drug delivery for chemotherapy [3], gene therapy [6], magnetic resonance imaging as contrast agents based on superparamagnetism [7], and molecular recognition [8].…”

Section: Introductionmentioning

confidence: 99%

Density matrix renormalization group algorithm for Bethe lattices of spin-12or spin-1 sites with Heisenberg antiferromagnetic exchange

2012

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An efficient density matrix renormalization group (DMRG) algorithm is presented for the Bethe lattice with connectivity Z = 3 and antiferromagnetic exchange between nearest neighbor spins s = 1/2 or 1 sites in successive generations g. The algorithm is accurate for s = 1 sites. The ground states are magnetic with spin S(g) = 2 g s, staggered magnetization that persists for large g > 20 and short-range spin correlation functions that decrease exponentially. A finite energy gap to S > S(g) leads to a magnetization plateau in the extended lattice. Closely similar DMRG results for s = 1/2 and 1 are interpreted in terms of an analytical three-site model.

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Heteroatom-Based Dendrimers

Cited by 37 publications

References 0 publications

Dendrimer Complexes Based on Fine-Controlled Metal Assembling

Dendrimer Complexes Based on Fine-Controlled Metal Assembling

Dendrimer-Encapsulated Metals and Semiconductors: Synthesis, Characterization, and Applications

Density matrix renormalization group algorithm for Bethe lattices of spin-12or spin-1 sites with Heisenberg antiferromagnetic exchange

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