Régis Laurent

Dendrimers : towards catalytic, material and biomedical uses

This book will be mainly focussed on the properties and uses of dendrimers and dendrons. The aim of this book is to be the reference book about dendrimers applications. It will not describe all details, but it will give the reader a unique overview of what has currently been done with dendrimers, with numerous references and illustrations. It will be divided in four main parts: Part 1) Generalities, syntheses, characterizations and properties; Part 2) Applications in catalysis; Part 3) Applications for the elaboration or modification of materials; and Part 4) Applications in biology/medicine. The role of the nanometric size and the multiple functions of dendrimers on the properties will be emphasized.

“Janus” dendrimers: syntheses and properties

“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.).

Dendritic phosphoramidite ligands for Rh-catalyzed [2+2+2] cycloaddition reactions: Unprecedented enhancement of enantiodiscrimination

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.

Chemistry in the internal voids of dendrimers

Abstract PN–PS linkages placed in some layers within dendritic architectures allow the grafting of several types of functional groups at site and depth specific places in the internal layers of phosphorus containing dendrimers. These functional groups are either organic derivatives (allyl, propargyl, isothiocyanate, amine, aldehyde, azide, crown-ether) or metallic derivatives (gold chloride, anionic zwitterionic zirconocene). Furthermore, the dendrimeric architecture is flexible enough to allow the growing of new dendrimers inside the internal voids of the initial dendrimer.

Influence of cationic phosphorus dendrimers on the surfactant-induced synthesis of mesostructured nanoporous silica

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.

Very large neutral and polyanionic Fe/Au cluster-containing dendrimers

Abstract Treatment of tetrahydrofuran solutions of a series of ClAu-terminated dendrimers with the iron anions [Fe2(CO)7(PPh2)]− and [Fe3(CO)11]2− has allowed the new dendrimer species decorated on the surface by Fe2Au or Fe3Au units to be isolated, including one having up to 192 Fe2Au clusters.

Synthesis of dye/fluorescent functionalized dendrons based on cyclotriphosphazene

Summary Functionalized phenols based on tyramine were synthesized in order to be selectively grafted on to hexachlorocyclotriphosphazene, affording a variety of functionalized dendrons of type AB5. The B functions comprised fluorescent groups (dansyl) or dyes (dabsyl), whereas the A function was provided by either an aldehyde or an amine. The characterization of these dendrons is reported. An unexpected behaviour of a fluorescent and water-soluble dendron based on dansyl groups in mixtures of dioxane/water was observed.

Organophosphorus chemistry for the synthesis of dendrimers.

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.

Ordered Layered Dendrimers Constructed from Two Known Dendrimer Families: Inheritance and Emergence of Properties

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 (31) P 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.

Original Multivalent Gold(III) and Dual Gold(III)–Copper(II) Conjugated Phosphorus Dendrimers as Potent Antitumoral and Antimicrobial Agents

Original metallophosphorus dendrimers (generation 3, 48 terminal groups) have been prepared via the complexation of phosphorus dendrimers bearing imino-pyridino end groups with Au(III) or with both Au(III) and Cu(II). The complexation of the dendrimer with Au(III), leading to 1G3-[Au48][AuCl4]48, strongly increased the antiproliferative activities against both KB and HL-60 tumoral cell lines, showing IC50s in the low nanomolar range. It can be noticed also that this gold conjugated phosphorus dendrimer displayed low activity on the quiescent cell line EPC versus its potent antiproliferative activity against actively dividing cells. In order to evaluate the potential synergistic effect between Au(III) and Cu(II) and the influence of the number of Au(III) moieties on the surface of dendrimer against the proliferative activities, nine other original dendrimers with several surface modifications have been prepared. Whatever the number of Au(III) moieties introduced on the surface of dendrimers, all the dendrimers prepared displayed similar potency (nanomolar range) to 1G3-[Au48][AuCl4]48 against KB and HL60. In marked contrast synergistic effects on the antimicrobial activity of some of these phosphorus dendrimers are observed when both Au(III) and Cu(II) are present on the dendritic structure.