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International audience; Dendrimers are highly branched macromolecules, which have properties in many different fields, in particular for catalysis. This review presents an exhaustive view about complexes of phosphorus-containing dendrimers (having a phosphorus atom at each branching point), used as homogeneous catalysts in a range of reactions. First, catalysed reactions for C–C bonds formation using Pd, Rh, Ru, or Sc complexes will be displayed; then formation of C–O and C–N bonds using Cu complexes as catalysts will be shown. At the end, miscellaneous reactions catalysed without metal (organocatalysis) will be displayed. Despite their size, dendrimers are generally soluble in the reaction media, thus they afford homogeneous catalysts. However, their size is by far larger than the size of the reagents and products, thus they are generally easily separated, simply by adding a solvent in which the products are soluble, but not the dendrimers. The recovery and reuse of dendrimers (recycling) is an important advantage compared to classical monomeric catalysts, which will be emphasized in this review, together with the so-called dendrimer (or dendritic) effect, which is an enhancement of a property when the size of the dendrimer increases.

Photodynamic therapy (PDT) is a skin cancer treatment alternative to chemotherapy and radiotherapy. This method exploits three elements: a phototoxic compound (photosensitizer), light source and oxygen. Upon irradiation by light of a specific wavelength, the photosensitizer generates reactive oxygen species triggering the cascade of reactions leading to cell death. The positive therapeutic effect of PDT may be limited due to low solubility, low tumor specificity and inefficient cellular uptake of photosensitizers. A promising approach to overcome these obstacles involves the use of nanocarrier systems. The aim of this initial study was to determine the potential of the application of phosphorus dendrimers as carriers of a photosensitizer&mdash, rose bengal (RB). The primary goal involved the synthesis and in vitro studies of covalent drug&ndash, dendrimer conjugates. Our approach allowed us to obtain RB&ndash, dendrimer conjugates with the use of tyramine as an aromatic linker between the carrier and the drug. The compounds were characterized by FT-IR, 1H NMR, 13C NMR, 31P NMR, size and zeta potential measurements and spectrofluorimetric analysis. The dialysis to check the drug release from the conjugate, flow cytometry to specify intracellular uptake, and singlet oxygen generation assay were also applied. Finally, we used MTT assay to determine the biological activity of the tested compounds. The results of our experiments indicate that the conjugation of RB to phosphorus dendrimers via the tyramine linker decreases photodynamic activity of RB.

International audience; First-in-class CuII and AuIII metaled phosphorus dendrons were synthesized and showed significant antiproliferative activity against several aggressive breast cancer cell lines. The data suggest that the cytotoxicity increases with reducing length of the alkyl chains, whereas the replacement of CuII with AuIII considerably increases the antiproliferative activity of metaled phosphorus dendrons. Very interestingly, we found that the cell death pathway is related to the nature of the metal complexed by the plain dendrons. CuII metaled dendrons showed a potent caspase-independent cell death pathway, whereas AuIII metaled dendrons displayed a caspase-dependent apoptotic pathway. The complexation of plain dendrons with AuIII increased the cellular lethality versus dendrons with CuII and promoted the translocation of Bax into the mitochondria and the release of Cytochrome C (Cyto C).

International audience; Pyridine, pyridine imine, and bipyridine imine ligands functionalized by a phenol have been synthesized and characterized, in many cases by X-ray diffraction. Several of these N-, N,N-, and N,N,N,-ligands have been grafted onto the surface of phosphorhydrazone dendrimers, from generation 1 to generation 3. The complexation ability of these monomers and dendrimers towards palladium(II) has been assayed. The corresponding complexes have been either isolated or prepared in situ. In both cases, the monomeric and dendritic complexes have been tested as catalysts in Heck couplings and in Sonogashira couplings. In some cases, a positive dendritic effect has been observed, that is, an increase of the catalytic efficiency proportional to the dendrimer generation.

International audience; Phosphorus dendrimers are highly branched macromolecules, built with one phosphorus atom at each branching point. These dendrimers can be functionalized at will on the terminal functions. Grafting as terminal functions ligands suitable for the complexation of copper has been carried out several times, in particular with the aim of using the corresponding complexes as catalysts in a range of reactions, from O-and N-arylations and-vinylations, to the asymmetric benzoylation of linear or cyclic diols. A sequel of this work concerns the study of anticancer activity of analogous dendritic copper complexes.

The study of chelating ligands is undoubtedly one of the most significant fields of research in chemistry. The present work is directed to the synthesis of new functionalized derivatives of tripodal C-scorpionate compounds. Tris-2,2,2-(1-pyrazolyl)ethanol, HOCH2C(pz)3 (1), one of the most important derivatives of hydrotris(pyrazolyl)methane, was used as a building block for the synthesis of new functionalized C-scorpionates, aiming to expand the scope of this unexplored class of compounds. The first dendritic C-scorpionate was successfully prepared and used in the important industrial catalytic reactions, Sonogashira and Heck C-C cross-couplings.

International audience; Phosphorhydrazone dendrimers ended by PTA (1,3,5-triaza-7-phosphaadamantane) derivatives are used for the complexation of ruthenium. The corresponding complexes, either isolated (synthesized ex situ, i.e. preformed) or generated in situ are used as catalysts for the hydration of phenylacetylene in various conditions (ex situ or in situ, quantities, temperature, duration, co-catalyst or not, recycling). The same preformed complexes are tested for their interaction with supercoiled DNA, to afford relaxed DNA.

Dendrimers are hyperbranched macromolecules, synthesized step by step (generation after generation) in an iterative fashion, which structure is reminiscent to that of the branches of trees. Most of their properties are due to their terminal functions, which can be easily modified at will to fulfill the desired properties. In particular, many types of catalytic entities have been used as terminal groups of dendrimers. In some cases, a dendritic effect , that is the enhancement of the catalytic properties when a catalyst is linked to a dendrimer, has been observed. It is also generally possible to recover and reuse the dendritic catalysts. The internal structure of dendrimers can also play a key-role, as it manages cavities which can accommodate the catalytic entities, and enable the substrates to interact with them. Catalytic sites included inside the structure of dendrimers are rare, excepted if they constitute the core of dendrimers (or of dendrons, which are dendritic wedges). Effect of the confinement on the catalysis outcome is generally the main aim of these works. Another type of dendritic catalytic entities taking profit of the internal structure concerns metallic nanoparticles used as core of dendrimers. In this chapter, we will gather information about catalytic entities included inside dendrimers, either covalently linked, or noncovalently entrapped, and on their syntheses. The main types of reactions studied, the role of the generation (size) of the dendrimers, their recovery and reuse, and in general the effect of the confinement inside the dendritic structures on the catalytic efficiency will be discussed.

Poly(phosphorhydrazone) dendrimers constitute a versatile class of dendrimers, which can be functionalized at will at all levels of the structure (surface, core, branches) with various types of ligands (mono-, bi-, multi-dentate ligands), suitable for the complexation of different types of metals, including transition metals, lanthanides, or alkaline earths. This review is organized depending on the type of ligands. The properties of the corresponding complexes have been studied in many cases, and will be given. Most of the properties concern catalysis; a positive dendrimeric effect has been observed in many cases when the generation of the dendrimer increases. In many cases it is possible to recover the catalyst and to reuse it (up to ten times with the same efficiency). Other properties concern the field of materials, with the functionalization of the surface of electrodes, in particular with ferrocene-containing dendrimers, or the elaboration of metallic nanoparticles, and even their organization in dendritic networks. A single example of property in the field of biology is given, but it constitutes a promising result as anti-proliferative agents against cancerous cells.

International audience; Dendrimers are hyperbranched macromolecules having a perfectly defined and multifunctionalized structure, constituted of branches emanating radially from a central core. The structure of dendrimers is particularly modular, and can incorporate in different parts coordination complexes. In this review, we will present the interplay between dendrimers and coordination chemistry in three main fields: catalysis, materials, and biology. Most of the examples will be taken from the work done with phosphorus-containing dendrimers, but the pioneering work carried out with other dendrimers will be also presented. One of the major improvements that metallodendrimers have afforded concerning catalysis is their easy recovery and reuse, bridging the gap between homogeneous and heterogeneous catalysis. Another major improvement concerns the “dendritic effect” which can afford impressive outcomes concerning the increase of yield and of enantioselectivity, together with a decrease of the leaching of metals, and consequently of waste. Dendrimers can be used also for the synthesis and stabilization of metallic nanoparticles, for the modification of metallic surfaces at the nanometric scale, and for the synthesis of mesoscopically ordered hybrid materials. Finally metallodendrimers have high potency against cancerous cell lines, and they appear to operate via a different mechanism of action compared with native metallodrugs, opening new avenues for the search of improved anti-cancer agents.

International audience; A new concept is presented, namely the synthesis of dendrimers intrinsically composed in alternation of building blocks pertaining to two known families of dendrimers: phosphorhydrazone dendrimers and triazine–piperazine dendrimers. These mixed dendrimers with layered controlled architecture inherit their easy 31P NMR characterization and their thermal stability from the phosphorhydrazone family, and their decreased solubility from the triazine–piperazine family. However, they have also their own and original characteristics. Both parent families are white powders, whereas the mixed dendrimers are yellow, orange, or red powders, depending on the generation. DFT calculations were carried out on model dendrons to understand these special color features. Remarkably, these dendrimers incorporating redox-active organic entities allow for the first time the monitoring of the growth of an organic dendrimer by electrochemistry while highlighting an even–odd generation behavior.

The use of dendrimers as soluble supports of catalytic entities offers efficient tools for “greener” catalysis. Indeed, thanks to their large size, dendrimers can be recovered and reused; depending on their structure, they can be tolerant to aqueous media or even soluble in water; and they can be used as ligands of cheap metals such as copper. We describe several examples of dendritic catalysts having such properties, based on the functionalization of phosphorus-containing dendrimers.

The synthesis of two new series of phosphorus-containing dendrimers capped by bis(diphenylphosphinomethyl)amino groups linked to either tyramine or l-tyrosine methyl ester is reported up to the third generation (48 end groups). The corresponding complexes obtained in situ by reaction with Pd(OAc)2 are used as catalysts in three types of C−C cross-coupling reactions, namely, Suzuki, Sonogashira, and Heck reactions, in the presence of water. A slightly positive dendritic effect is observed in the case of the Sonogashira reaction: the conversion increases when the generation (size and number of end groups) of the dendritic catalyst increases. In all cases, the series built from tyramine is more efficient than the series built from l-tyrosine, showing the influence of the local hindrance, and the dendrimers are generally more efficient than the corresponding monomers.

Dendrimers are hyperbranched nanosized and precisely defined molecules, attracting increasing attention each year due to their numerous properties in catalysis, materials science, and biology. This tutorial review concerns the use of dendrimers as catalysts and focuses more precisely on their properties as enantioselective catalysts. Emphasis is put on chiral phosphine complexes constituting the core or the end groups of various types of dendrimers. The effect of the location of the catalytic entities, the effect of the size (generation) and the nature of the dendritic skeleton on the enantiomeric excesses are discussed.

Dendrimer are hyperbranched macromolecules, which can be used as support of catalytic entities. This review focusses on polyphosphorhydrazone (PPH) dendrimers, bearing as terminal groups, transition metal complexes of 3d elements (Cu, Sc) and 4d elements (Pd, Ru, Rh). These complexes have been used as catalysts for various organic reactions, in particular C–C couplings. Most of these dendritic complexes can be recovered and re-used several times (up to 12 successive runs with the same efficiency). In several cases, a dendritic (or dendrimer) effect is observed, i.e., an increased efficiency and/or enantioselectivity when comparing a monomeric catalyst with increasing generations of the dendrimers, using in all cases the same number of catalytic entities.

International audience; Dendrimer are hyperbranched macromolecules, which can be used as support of catalytic entities. This review focusses on polyphosphorhydrazone (PPH) dendrimers, bearing as terminal groups, transition metal complexes of 3d elements (Cu, Sc) and 4d elements (Pd, Ru, Rh). These complexes have been used as catalysts for various organic reactions, in particular C–C couplings. Most of these dendritic complexes can be recovered and re-used several times (up to 12 successive runs with the same efficiency). In several cases, a dendritic (or dendrimer) effect is observed, i.e., an increased efficiency and/or enantioselectivity when comparing a monomeric catalyst with increasing generations of the dendrimers, using in all cases the same number of catalytic entities.

The influence of the size (the generation) of phosphorus dendrimers on their properties is discussed in three main fields of applications: catalysis, new materials, and biology. Typical examples are given to illustrate these three fields: Knoevenagel condensation for catalysis, elaboration of highly sensitive DNA chips for materials, transfection experiments, and anti-prion activity for biology.

The synthesis of a third generation phosphorus-containing dendrimer possessing 24 chiral iminophosphine end groups derived from (2S)-2-amino-1-(diphenylphosphinyl)-3-methylbutane is described. In situ complexation of this dendrimer by [Pd(η3-C3H5)Cl]2 affords a catalyst, which is used in asymmetric allylic alkylations of rac-(E)-diphenyl-2-propenyl acetate and pivalate. The percentage of conversion, the yield of isolated 2-(1,3-diphenylallyl)-malonic acid dimethyl ester, and its enantiomeric excess have been measured in each case, and were found to be good to very good (ee from 90% to 95%). Furthermore, the dendritic catalyst can be recovered and reused at least two times, with almost the same efficiency.

A third generation dendron possessing one activated vinyl group linked to the core and 16 chlorines linked to the surface has been functionalized with various groups at the core (primary amine, phosphine, or azide), and on the surface (aldehyde, tertiary amine, or nitrile). These functionalized dendrons are used as building blocks for the synthesis of several complex dendritic architectures, obtained through core−core, core−surface, or core−core−surface−core couplings using very simple one-step reactions between these functions, such as Michael additions between vinyl and primary amino groups or Staudinger reactions between phosphines and azides. These reactions finally induce the formation of layer-block dendrons, a surface-block dendrimer, a layer-block dendrimer, a layered surface-block dendrimer, and a segment-block dendrimer, all issued from the same original dendron.

Phosphorus dendrimers containing terminal phosphoramidite ligands have been found to be highly effective and recoverable catalysts for the rhodium(I) catalyzed [2+2+2] cycloaddition reactions. A strong positive dendritic effect is observed both in the activity and enantiodiscrimination leading to axially chiral biaryl compounds.

International audience; Dendrimers are multifunctional, hyperbranched and perfectly defined macromolecules, synthesized layer after layer in an iterative manner. Besides the nature of the terminal groups responsible for most of the properties, the nature of the internal structure, and more precisely of the branching points, is also of crucial importance. For more than 15 years, we have demonstrated that the presence of phosphorus atom(s) at each branching point of the dendrimeric structure is particularly important and highly valuable for three main reasons: (i) the versatility of phosphorus chemistry that allows diversified organochemistry for the synthesis of dendrimers; (ii) the use of 31P-NMR, which is a highly valuable tool for the characterization of dendrimers; (iii) some properties (in the fields of catalysis, materials, and especially biology), that are directly connected to the nature of the internal structure and of the branching points. This review will give an overview of the methods of synthesis of phosphorus-containing dendrimers, as well on the ways to graft phosphorus derivatives as terminal groups, with emphasis on the various roles played by the chemistry of phosphorus

We report the synthesis of a dense dendrimer ended by the PTA ligand (1,3,5-triaza-7-phosphaadamantane), and the use of the corresponding Rh and Ru complexes for catalysis. The catalytic properties of these dendrimers are compared with those of two other dendrimers: a dendrimer of the same generation but having half the number of ligands, and a dendrimer of the next generation, but having the same number of ligands. The positive influence of the density of catalytic sites on the surface of these dendrimers for alcohol isomerization in water has been evidenced.

International audience; “Janus” dendrimers, i.e.dendrimers constituted of two dendrimeric wedges and terminated by two different functionalities, are reviewed. Both the synthetic aspects and the particular properties afforded by the presence of two different functions in two precise areas of the surface of the Janus dendrimers are reported. This review is organized depending on the type of internal structure (benzyl ether, phenylene, phosphorus, PAMAM, DAB, lysine, alkyl ether, ester, amide, etc.).

Ene reactions involving carbonyl enophiles have been carried out under microwave irradiation at controlled temperature and atmospheric pressure. The reactions of diethyl mesoxalate with 1-decene and β-pinene and the cyclization of (+)-citronellal under homogeneous (neat liquid) or heterogeneous (clay catalyst) conditions have been studied. In each case the dependence of reaction yield on time and the stereoisomer ratios of the products are unaffected by the heating mode

Ene reactions involving carbonyl enophiles have been carried out under microwave irradiation at controlled temperature and atmospheric pressure. The reactions of diethyl mesoxalate with 1-decene and β-pinene and the cyclization of (+)-citronellal under homogeneous (neat liquid) or heterogeneous (clay catalyst) conditions have been studied. In each case the dependence of reaction yield on time and the stereoisomer ratios of the products are unaffected by the heating mode

Generations 1 to 3 of dendrimers ended by water-soluble phosphines are synthesized and their ruthenium complexes are used as catalysts in aqueous media; a slightly positive dendritic effect on the regioselectivity is observed for hydration of alkynes and a large positive dendritic effect is observed in the biphasic (water/heptane) catalysed isomerisation of allylic alcohols to ketones where the products are easily isolated and the catalyst can be reused several times, even the first generation.

Dendrimers are hyperbranched nanosized and precisely defined molecules, attracting increasing attention each year due to their numerous properties in catalysis, materials science, and biology. This tutorial review concerns the use of dendrimers as catalysts and focuses more precisely on their properties as enantioselective catalysts. Emphasis is put on chiral phosphine complexes constituting the core or the end groups of various types of dendrimers. The effect of the location of the catalytic entities, the effect of the size (generation) and the nature of the dendritic skeleton on the enantiomeric excesses are discussed.

The concomitant use of polycationic dendrimers and cationic surfactants for the elaboration of periodic mesoporous silica of type MCM-41 is described. The hexagonal structure is preserved up to about 26% in weight of dendrimer included in the silica. The cationic surfactant can be selectively removed to liberate the pores, while preserving the non-covalently incorporated dendrimers. These dendrimers included in the mesoporous silica are fully accessible through the mesoporous volume to small molecules such as HCl and tetrahydrofuran.

Imino pyridine-capped phosphorus dendrimers were found to strongly enhance the catalytic activity of copper in arylations and vinylations of O- and N-nucleophiles. These reactions could indeed be performed under very mild conditions, often the mildest to date. Interestingly, such performances could not be obtained when using the monomeric imino pyridine chelating ligand alone. To the best of our knowledge, this constitutes a rare example of such a positive dendritic effect in the field of organometallic catalysis.

Phosphorus dendrimers containing terminal phosphoramidite ligands have been found to be highly effective and recoverable catalysts for the rhodium(i) catalyzed [2+2+2] cycloaddition reactions. A strong positive dendritic effect is observed both in the activity and enantiodiscrimination leading to axially chiral biaryl compounds We would like to thank the Spanish MICINN (project CTQ2011-23121), the Generalitat de Catalunya (project 2009SGR637) and the CNRS (France) for their financial support. L. G. thanks the Universitat de Girona (UdG) for a predoctoral fellowship

This paper is a review concerning metallic derivatives linked to the surface of phosphorus-containing dendrimers, that are dendrimers possessing one phosphorus at each branching point. The synthetic aspects will be described first, concerning in particular the complexation of transition metals (Fe, W, Rh, Pt, Pd, Ru) by monophosphine or diphosphine end groups, the grafting of metallocene derivatives (zirconocene and ferrocene), and the interaction with various clusters (Au-Fe, Au, Ti). Some applications of these metallo phosphorus dendrimers will be described in the field of materials science (modification of the surface of existing materials or creation of new materials), and in the field of catalysis (Stille couplings, Knoevenagel condensations, Michael additions).

Linear 1,2,3,4-heterohexatrienes of type H 2 C=CHP(R) 2 =NP(R') 2 =X (X = O, S) are used in Michael-type additions of various primary or secondary amines and hydrazines. The use of functionalized amines allowed the grafting of other functions, such as a double or a triple bond, a sulfide, an imidazole, or a phenol, and various types of NH 2 groups. These groups were used in condensation reactions, leading to the grafting of new functions such as phenols. Thus, the P(R) 2 =NP(R') 2 =X group appears as a new electron withdrawing group, very easily tunable by changing the R' or X substituents.