Polypropylene amine dendrimers

Vogtle F, Gestermann S, Kauffmann C et al (2000) Coordination of C02+ ions in the interior of polypropylene amine) dendrimers containing fluorescent dansyl units in the periphery. J Am Chem Soc 122 10389-10404... 

Fe2(III,III)2+ states. By considering that organometallic dendrimers based on conjugated ferrocene units are of special importance since mixed-valence states have interesting electrical, redox, and magnetic properties, recently three generations of polypropylene amine) dendrimers, decorated at their periphery with 4, 8, and 16 (compound 6, Fig. 6.6a) BFc units, respectively, have been synthesized and the electrochemical behavior of the dendrimers complexed with (3-cyclodextrins ([3-CD) and adsorbed at self-assembled monolayers (SAMs) of heptathioether-functionalized [3-CD on gold (molecular printboard) has been studied.40... 

The first family of polycationic cobaltocenium dendrimers reported in the literature is constituted by four generations of the diaminobutane-based polypropylene amine) dendrimers containing 4, 8, 16, and 32 (compound 7 in Fig. 6.7a) cobaltocenium peripheral units, respectively.41... 

Carbon-based sorbents are relatively new materials for the analysis of noble metal samples of different origin [78-84]. The separation and enrichment of palladium from water, fly ash, and road dust samples on oxidized carbon nanotubes (preconcentration factor of 165) [83] palladium from road dust samples on dithiocarbamate-coated fullerene Cso (sorption efficiency of 99.2 %) [78], and rhodium on multiwalled carbon nanotubes modified with polyacrylonitrile (preconcentration factor of 120) [80] are examples of the application of various carbon-based sorbents for extraction of noble metals from environmental samples. Sorption of Au(III) and Pd(ll) on hybrid material of multiwalled carbon nanotubes grafted with polypropylene amine dendrimers prior to their determination in food and environmental samples has recently been described [84]. Recent application of ion-imprinted polymers using various chelate complexes for SPE of noble metals such as Pt [85] and Pd [86] from environmental samples can be mentioned. Hydrophobic noble metal complexes undergo separation by extraction under cloud point extraction systems, for example, extraction of Pt, Pd, and Au with N, A-dihexyl-A -benzylthiourea-Triton X-114 from sea water and dust samples [87]. 

Behbahani, M., Gorji, T., Mahyari, M., Salarian, M., Bagheri, A., Shaabani, A. Application of polypropylene amine dendrimers (POPAM)-Grafted MWCNTs hybrid materials as a new sorbent for solid-phase extraction and trace determination of gold(III) and palladium(II) in food and environmental samples. Food Anal. Methods 7, 957-966 (2014)... 

In a way related are the complexes formed by Hg salts and multicrown dendrimers of different generations (dendrimers with a polypropylene amine interior of different volume and benzo[15]-crown-5 ether periphery), studied by extraction methods using radioactive 203Hg2+.210 Up to 12 Hg2+ ions were found to be bound per dendrimer molecule, obviously in the amine-dominated interior, not in the crown-ether periphery. 

The history of dendrimer chemistry can be traced to the foundations laid down by Flory [34] over fifty years ago, particularly his studies concerning macro-molecular networks and branched polymers. More than two decades after Flory s initial groundwork (1978) Vogtle et al. [28] reported the synthesis and characterization of the first example of a cascade molecule. Michael-type addition of a primary amine to acrylonitrile (the linear monomer) afforded a tertiary amine with two arms. Subsequent reduction of the nitriles afforded a new diamine, which, upon repetition of this simple synthetic sequence, provided the desired tetraamine (1, Fig. 2) thus the advent of the iterative synthetic process and the construction of branched macromolecular architectures was at hand. Further growth of Vogtle s original dendrimer was impeded due to difficulties associated with nitrile reduction, which was later circumvented [35, 36]. This procedure eventually led to DSM s commercially available polypropylene imine) dendrimers. 

Figure 16.17 Amine-terminated polypropylene imine) dendrimers act as tridentate ligands for the complexation of transition metals [217] (a), and can function as templates for the assembly of Troger s base dizinc(ll) bis-porphyrin molecules, (b) [218]...

Figure 26.4 Plot of the glass transition temperatures of the polypropylene imine) dendrimers with nitrile ( ) and amine ( ) end-groups...

All dendrimers consist of inner tertiary amines, located at the branching points of the various dendritic shells (layers). The amine-terminated dendrimers, furthermore, have basic primary amine end-groups. Basicity is therefore one of the most dramatic properties of the polypropylene imine) dendrimers, and has been studied via titration experiments and calculations. Titration experiments of the dendrimers have been performed in water using 1 M hydrochloric acid. Only two equivalence points are observed for DAB-J nJr-(NH2)4 in a ratio of 2 1. From these titrations, pKa values of 10.0 (primary amine groups) and 6.7 (tertiary... 

Figure 14.1 Common commercially available dendrimers. Top left Polypropylene imine) dendrimer (G5). Top right Poly(amido amine) dendrimer (G3). Bottom Poly(amido amine) ( Starburst ) dendrimer (G5). Each generation is marked with a circle (reproduced by permission of The Royal Society of Chemistry).

The first examples of metallated phosphine-functionalized dendrimers that were suitable as homogeneous catalysts were reported by Reetz et al. [42], DAB-based phosphino dendrimers were synthesized from the commercially available DAB-polypropylene imine dendrimers (DAB = 1,4-diaminobutane) via a double phosphination of the amines with diphenylphosphine and formaldehyde. These dendrimers were loaded with Pd(II) centers by the reaction of the phosphine-functionalized dendrimer with [Pd(Me)2(tmeda)] (tmeda = tetramethylethylenediamine), in which the diphenylphosphino end groups act as a bidentate ligand (Scheme 6). 

Polypropylene imine) dendrimers (see Scheme 1 for structure) have been constructed step by step onto an amine functionalized polystyrene [38, 130, 131]. The challenge in this synthesis is finding conditions for the polypropylene imine) synthesis under which the low MW polystyrene (MW=3200) is soluble [38]. Similar poly(imine) dendrimers with carboxylic acid end groups have also been prepared [130]. The polypropylene imine) dendrimer has also been synthesized on an amino-terminated poly(2-methyl-2-oxazoline) [132]. 

The grafting from method is also successful in other ring opening polymerizations. For example, -caprolactone polymerization is initiated from polypropylene imine) dendrimers with n=2-16 end-standing amine groups [135]. To be... 

Nonetheless, it was a fairly short step from octopus compounds to dendrimers, and the step was taken by Vogtle in the late 1970s when he attempted to use a cascade reaction to prepare a molecule of the dendrimer type that would now be considered a dendron rather than a fully developed dendrimer. It began with the addition of acrylonitrile to an amine, followed by reduction of the nitrile to amine. This was followed by a further reaction with acrylonitrile, and the process was repeated several times to yield highly branched macromolecules. There were initially problems with the reduction step but these were overcome, and the preparation of these polypropylene imine) dendrimers was later commercialized. 

Polypropylene amines, poly(amidoamines) (PAMAM) and silicon dendrimers set records for the number of generations, whereas the polyacetylene dendrimer prepared by Moore et al. [6] with the formula C1398H1278 and a mass of 18079.53 holds the heavyweight championship title of pure hydrocarbons. Mullen et al. have recently published a series of aromatic hydrocarbon dendrimers consisting of phenylene-bridged benzene rings. [7] Interestingly, these species form two-dimensional planes rather than three-dimensionally extended structures. 

Co(III) and NaBH4. Iterative repetition of these two steps allows one to obtain cascade polymers , as Vogtle initially described them, but in poor yields. Optimization of Vdgtle s original inefficient synthesis by Meijer and Mulhaupt in 1993 resulted in the preparation of poly(propylenimine) dendrimers (Scheme 13.9). The high yield and degree of purity obtained in this synthesis has made these dendrimers one of the most popular architectures in dendrimer chemistry. They have also been produced on an industrial scale and can be found under different names, in particular PPI (for polypropylenimine), DAB (for diaminobutane) and POPAM (for polypropylene amine), depending on the nature of the core. 

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