Cluster dendrimers

In solution, it was solvent, not dendrimer environment, that dominated the environment and thus the redox potential. The same conclusions were made when we studied similar films of iron-sulfur cluster dendrimer isomers of the form [Fe4S4(Lig)4]2 described above.187... 

Advances in techniques include sophisticated NMR methods, both in solution and the solid-state, and computational methods, and these, coupled with X-ray diffraction and other established methods, have been applied to the study of a wide variety of structures. Topics covered in the book include Sn(II) clusters, tin Zintl ions, Sn(II) heterobimetallic compounds, RsSn+ cations, stannylenes (R2Sn ), stannenes (R2Sn=SnR2 and R2Sn=CR2), stannynes (RSn=SnR), organotin oxide, carboxylate and sulfonate clusters, dendrimers and macrocycles, organotin polymers, Sh-tt interactions, unusual bondings and structures, and compounds with non-linear optical properties. 

Fig. 25 Scheme showing the stmcture of an iron-sulfur cluster dendrimer and a Frechet-type iron porphyrin dendrimer... 

Dendrimers can be assembled into multimolecular assemblies called megamers. In some cases, this is because of the natural clustering of dendrimer... 

This is a very new field, but given the current interest in both dendrimer chemistry and supramolecular chemistry, it is one that is likely to receive attention in the future. The prospect of preparing well-defined molecular assemblies, rather than ill-defined clusters, is attractive, and is expected to give access to new properties that can be controlled by the molecular architecture of the assembly. New and useful materials seem likely to emerge as this chemistry grows and is exploited in the years to come. 

We have found that dendrimers can be used to encapsulate active moieties, thereby preventing them from interacting. This passivation effect limits inter-molecular interactions such as self-aggregation and molecular clustering. We also found that dendrimers can be made dipolar. This asymmetry in molecular orientation enables dendrimers to be used in NLO. In this chapter we describe our application of dendrimers to lasers and NLO. 

Figure 19 explains what in principle happens the cluster monolayer on the dendrimer film is mobilized by means of CH2CI2 vapour (a b). The phosphines are then removed by the SH functions (b->c). The bare AU55 nanoclusters move between the dendrimer molecules to form crystals (Auss) which finally appear on the surface (c d). The formation of crystalline superlattices of naked AU55 particles proves their stability which is founded in their perfect cuboctahedral shape. The (Auss) species is a novel modification of the element gold. 

Figure 80 A first-generation organometallic dendrimer (145) containing grafted carborane clusters on tetra(terpyridine) cores. (Adapted from ref. 159.)... 

Precise placement of metal complexing sites within the infrastructure of a cascade molecule is of importance from a variety of perspectives. In the construction of the above noted Micellane family (cf. Sect. 3.1), we reported the construction of dendrimers with four alkyne moieties at sites equidistant from each other in the interior (17, Fig. 8) [60]. These were treated with decaborane (B10H14) to afford 1,2-dicarba-closo-dodecaboranes (o-carboranes) [71]. Rendering boron clusters soluble in water is of interest because of their use in cancer treatment by Boron Neutron Cancer Therapy. First and second generation water-soluble dendrimers containing four and twelve precisely located boron cluster sites, respectively, were synthesized (e.g., 18). These water soluble dendrimers and their precursors were characterized by 13C-, and nB-NMR spectroscopy (Fig. 8). 

In continuing efforts, the same authors constructed tris(galactoside)-modified DAB dendrimers by the accelerated convergent strategy. In this particular approach, the saccharides were connected first to a small TRIS branching derivative to form a cluster which served as a building block, once suitably functionalized.417 N-Succini-midyl-activated ester 561 was then coupled onto G(l) and G(2)-PPI dendrimers with... 

In summary, results of in vivo experiments showed the effectiveness of carbosilane dendrimers having clustered Pk carbohydrate moieties, and the complete neutralization potency against STL-II was discovered when dumbbell-shaped dendrimers were identified as potent candidate inibitors. Although the precise mechanism of action remains to be elucidated, this type of inhibitor provided a new strategy for the detoxification of SLTs present in circulation. 

H. Oka, T. Onaga, T. Koyama, C.-T. Guo, Y. Suzuki, Y. Esumi, K. Hatano, D. Temnuma, and K. Matsuoka, Sialyl 7(2 3) lactose clusters using carbosilane dendrimer core scaffolds as influenza hemagglutinin blockers, Bioorg. Med. Chem. Lett., 18 (2008) 4405 1408. 

Dendrimer interior functional groups and cavities can retain guest molecules selectively, depending on the nature of the guest and the dendritic endoreceptors, the cavity size, the structure, and the chemical composition of the peripheric groups. Two main methods are known for the synthesis of metal nanoparticles inside dendrimers. The first method consists of the direct reduction of dendrimer-encapsulated metal ions (Scheme 9.4) the second method corresponds to the displacement of less-noble metal clusters with more noble elements [54]. 

A. Kimoto, J. Cho, M. Higuchi, and K. Yamamoto, Novel carbazole dendrimers having a metal coordination site as a unique hole-transport material, Macromolecular Symposia 209 (Organo-metallic and Coordination Clusters and Polymers) pp. 51-65 (2004). 

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