Dendrimers coordinated arene complexes

There has been a great deal of interest in the design of dendrimers using arene complexes of transition metals (246-252). Astruc has developed an efficient route to core molecules suitable for the synthesis of star and dendritic materials via peralkylation or allylation of methyl-substituted arene complexes of cyclopen-tadienyliron. The resulting branched polymers contained cationic cyclopentadi-enyliron moieties at the core and/or the periphery. Complexes containing aryl ethers coordinated to six CpFe+ moieties (110) were synthesized via SNAr reactions (248). 

There are numerous examples of dendrimers and star polymers containing metal coordination complexes (253-259). The synthesis of polypsrridine ruthenium coordination complexes incorporating Fe and Co (113) has been established (255). A ruthenium star-shaped complex with a CpFe" "-coordinated arene as the core has also been reported (254). 

Astruc and coworkers have reported the synthesis of highly branched polymers coordinated to cyclopentadienyliron and pentamethylcyclopentadienyl-ruthe-niiun cations." The catalytic and sensing ability of star polymers and dendrimers has also been reviewed. Multifunctional core molecules suitable for the synthesis of star and dendritic materials were synthesized by peralkylation or aUylation of methyl-substituted arene complexes of cyclopentadienyliron." The benzylic protons on these complexed arenes are acidic, which permits their facile alkylation. These branched polymers contained cationic cyclopentadienyliron moieties at the core and/or the periphery. The synthesis of a water-soluble metallodendrimers... 

There are numerous examples of dendrimers and star polymers that contain metal coordination complexes based on pyridine ligands. There is also interest in the incorporation of more than one type of metal complex into these materials. Constable and coworkers have reported the synthesis of heptametallic complexes containing six peripheral ruthenium coordination complexes and a central iron or cobalt complex. Scheme 21 illustrates the reaction of 89 with either iron or cobalt complexes to produce the heptametallic dendrimer 90. A heptametallic star-shaped complex with a CpFe -coordinated arene as the core and ruthenium Aexa-pyridine complexes at the periphery has also been reported by Astruc. ... 

A first generation poly(amido amine) dendrimer has been functionalized with three calyx[4]arenes, each carrying a pyrene fluorophore (4) [30]. In acetonitrile solution the emission spectrum shows both the monomer and the excimer emission band, typical of the pyrene chromophore. Upon addition of Al3+ as perchlorate salt, a decrease in the excimer emission and a consequent revival of the monomer emission is observed. This can be interpreted as a change in the dendrimer structure and flexibility upon metal ion complexation that inhibits close proximity of pyrenyl units, thus decreasing the excimer formation probability. 1H NMR studies of dendrimer 4 revealed marked differences upon Al3+ addition only in the chemical shifts of the CH2 protons linked to the central amine group, demonstrating that the metal ion is coordinated by the dendrimer core. MALDI-TOF experiments gave evidence of a 1 1 complex. Similar results have been obtained for In3+, while other cations such as Ag+, Cd2+, and Zn2+ do not affect the luminescence properties of... 

Various first-generation dendrimers and star-shaped molecules were generated from the nucleophilic aromatic substitution of chlorosubstituted arenes coordinated to cyclopentadienyliron complexes (Schemes 2.68 and 2.69). These compounds contained either ether or ester bridges. The star-shaped molecules prepared with ether bridges showed a decrease in solubility with an increase in star size, whereas the incorporation of ester bridges resulted in a decrease... 

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