The chemistry of cascade molecules (or dendrimers)"' has allowed the construction of macromolecular assemblies possessing vast numbers of precisely juxtaposed nuclei by the iterative connection of multifunctional building blocks. A notable feature of the dendritic method is the ability to control spatial or topological relationships between similar and dissimilar macromolecular subunits incorporated into a branched polymeric framework. Consequently, this controlled synthesis of branched (or linear) macroassemblies has potential in such areas of supramolecular chemistry as molecular devices ['] and molecular information processing.['] Thus, the potential creation of precisely ordered dendritic "superclusters" or "networks"[41 has provided the impetus for the investigation of definite dendritic con.jointment. Reports of contructing cascade molecules by connecting preconstructed dendrimers as macroassembly subunits include the random, nonspecific linking of "starburst dendrimers" t o yield "starburst polymers"[51 and the highly branched poly(ary1amide) polymers.[6] Specific connectivity is noted in the connection of dendritic wedges with both ends of polyethylene glycol or polyethylene oxide producing polyethereal copolymer^,['^ in the trapping of living polystyrene to afford linear globular ABA copolymers,l8I and in the attachment of dendrimers to a polyfunctional core.["' lo, ' I We now report the ruthenium-mediated assembly of a novel series of well-defined cascade macroassemblies" 21 possessing maximal 1 + 3 branching multiplicity a t a carbon atom. The use of a ruthenium(1r) metal center ( < Ru > ) [ 1 3 ] allowed the formation of stable complexes between the discrete terpyridine receptor units attached to different cascade macromolecules. Since the proof of the structure of specific organic networks is often difficult. the use of metal spacers will help to establish the network patterns. The electrochemical results presented here for the complexes. when compared to those of several model systems. c1e:irly establish the presence of the < Ru> center bound to two 0-substituted terpyridine ligands. These results, coupled with the other spectroscopic evidence and the synthetic strategy utilized. confirm the presence of the bis-dendrimers. Used in this fashion. electrochemical results become useful tools for rapid assessment of the structure of nanoscopic complex formation. The second-tier, metal-cascade molecule 9 < Ru (Scheme 1) was prepared in the following manner: 4-chloro-2.2': 6'2"-terp~r i d i n e [ '~I (3) and I-hydroxydodecanoic acid (1) were converted with KOH in DMSO into the terpyridinecnrboxylic acid 4.Peptide-type coupling of 4 with amine 6 under standard condit i o n~[ '~] led to triester 7a, which was readily hydrolyzed to the corresponding polyacid 7b. Repetition of the amide coupling gave the well-defined nonaester 9. Treatment of 7a and 9 with RuCI, ' 3 H,O generated the desired Ru-containing cascades (7a < Ru and 9 < Ru). as microcrystalline, paramagnetic, orange-brown complexes. Because of th...
Molecular recognition of glutarimide using 2,6-diamidopyridine units incorporated into dendritic building blocks is examined.
Mit dem gezielten Einbau von Terpyridin‐Metallkomplexen lassen sich, wie im Bild rechts schematisch dargestellt, zwei Dendrimere definiert miteinander verknüpfen. Die elektronischen Eigenschaften des Metallzentrums hängen dabei von der Dendrimerumgebung ab.
A series of fourfold functionalized 2,ll-dithia-and 2,11-shaped molecules of type 24 by macrocyclization reactions of diaza [3.3]cyclophanes 15 -l? and 18 -22, resp., is prepared by e. g. 21 and 22. Macrocycle 24 turns out to be conformationally using a new multistep-strategy starting from 7 or m-xylene,
The construction of cascade polymers with novel properties is discussed. A flexible amide‐based cascade architecture facilitates changes of the molecular hydrodynamic radius as a function of environmental pH, provided that the periphery is coated with ionizable functional groups (e.g., carboxylic acids or amines). Thus, it is possible to expand or contract the internal void domains within these cascades. By extension of the heteroatom connectivity, we have prepared a novel multifunctional molecule possessing a predetermined spherical morphology, that utilizes a ruthenium(II) metal center coordinated to two different orthogonal 2,2':6',2″‐terpyridine moieties to build the arm(s) of the cascade polymer. This technology permits the placement of multiple metal complexes at predetermined internal sites within the hydrophilic‐surfaced MicellaneTM framework. The combination of these two strategies to build cascade polymers allows the creation of an unsymmetrical bolaamphiphile constructed from two separate and distinct macromolecules. We are able to build cascade molecules either with a terpyridine unit inside or outside the polyamide sphere. The use of a connecting ruthenium(II) center allows the specific formation of a stable complex between the discrete cascade polymers.
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