Dendritic assembly

Figure 1.6 Examples of (a) branch cell, (b) dendritic assembly of branch cells and (c) crosslinked nano-networks derived from branch cells...

Here, we review the basic features of the metal-polypyridine building blocks, their redox properties, and the way such properties are connected with the ideal topography of dendritic assembly that determines the desired antenna effect. 

The neutral and cationic [Pd(II)NCN] pincer-containing dendritic assemblies 14 and 15 have been used as Lewis acid catalysts in the aldol condensation of benzaldehyde and methyl isocyanoacetate. These showed conversions, turnover frequencies and cis/trans ratios of the oxazoline products that were essentially identical to those of the monomeric model complex applied in the same reaction. 

This supramolecular dendritic assembly serves as a valuable soluble model for the interaction of perfluoro-tagged catalysts with insoluble supports such as fluorous silica gel and clearly reveals the ligand diffusion from the complex at elevated temperatures. This behavior can also explain the high catalytic activity of the heterogeneous FPS system. 

The introduction of chirality into dendritic assemblies can be easily addressed as shown for Figure 3.4,[l5 which would be named 6-Cascade benzene[3-l,3,5] (5-(3S,4S-l,6-dioxa-3,4-Oisopropylidene-3,4-dihydroxyhexyl)-l,3-phenylene) 4-(3S,4S-l,6-dioxa-3,4-0-isopropylidene-3,4-dihydroxyhexyl)-rm-butylbenzene. 

Connection of dendrimers via treatment with multifunctional cross-linking-type reagents such as the addition of polyhalides to amine-terminated dendrimers 78 results in randomly positioned dendritic assemblies. Dendrimers have also been bridged by the incorporation of copolymerizable units into reactions with dendrimers possessing polymerizable, terminal olefins. 79,80 ... 

Therefore, we connected the tri-urea 27 with three tetra-ureas 28, via covalent linkers, to a building block A. In apolar solvents molecules A alone would form crosslinked polymers via dimeric substructures formed by the tri- and tetra-ureas. Together with the building block B, a tetra-tosylurea substituted by four phthalimido alkylether residues, this polyassociation is prevented by the formation of heterodimers between tetra-aryl- and tetra-tosylureas. A solution of A and B in the ratio 2 6 therefore contains exclusively the dendritic assembly shown in Figure 5.21, as proved by light scattering and DOSY NMR spectroscopy [69]. 

Smith and co-workers prepared the dendritic assembly 190 from two L-lysine dendrons, bearing a benzo-18-crown -6 unit at the focal point, and l,4-bis(aminomethyl)benzene dihydrochloride. They then studied by NMR analysis the disassembly process induced by addition of potassium ions <2002AGE3254, 2003T3999>. 

Fig. 11 Formation of aggregates from dendritic-assembly a aggregates in (CHCI3/ M-hexane = 5/5) b in toluene c in water (d, e, f) stabilization of the aggregates via UV-irradiation. Reprinted with permission from [73]...

Metal-functionalized dendritic assemblies have been demonstrated to be a fertile area with competitive potential for purely organic structures for their photonic properties [29]. This chapter aims at providing on overview of the different outstanding possibilities that dendrimers advantageously offer, first from a fundamental perspective by describing the main routes to build these nanometer-sized species, and then, by describing their photophysical properties, and eventually to the applications developed for these materials in various areas. 

MAP2 42.000 and 200.000 Dendrites Assembles and cross-links MTs to one another and to intermediate filaments... 

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