Catalysis inside dendrimers

Abstract

Catalytic sites can be placed at the core, at interior positions or at the periphery of a dendrimer. There are many examples of the use of peripherally functionalized dendrimers in catalysis and this subject has been thoroughly reviewed in the recent literature. This review is concerned only with dendrimer based catalysis involving catalytic sites at the core of a dendrimer and within the interior voids. In covering the significant achievements in this area, we have concentrated on examples that highlight key features with respect to positive and/or negative catalytic activity.

Self-Assembled Nanoreactors

“…In the last case, the catalytic site is protected by the dendritic branches, resulting in an enzyme mimic. In general, three types of dendrimer nanoreactors can be distinguished: (i) dendrimers with a catalytically active core, 261,262 (ii) free-energy driven dendrimer nanoreactors, which are not directly involved in the reaction, 264 and (iii) dendrimers that stabilize a catalytically active metal nanoparticle (Scheme 12). 260 The results obtained with these types of dendrimer nanoreactors in catalysis vary greatly, but in general the dendrimers have an added value, that is, by stabilizing the catalytically active center, by increasing the stereo-and regioselectivity of the reaction, and by allowing easy recovery of the catalyst, for example, by filtration or precipitation.…”

“…259 The use of dendrimers in catalysis is well documented in the literature and is described in a number of reviews. [259][260][261][262][263][264][265] Covalently attached catalytic sites in dendrimers can be present at the periphery, at intermediate places, or can constitute the center of the dendrimer. In the last case, the catalytic site is protected by the dendritic branches, resulting in an enzyme mimic.…”

Where organometallics and dendrimers merge: the incorporation of organometallic species into dendritic molecules

“…The mononuclear Josiphos ligand system was proven to be an effective support for Rh-catalyzed asymmetric hydrogenation of alkenes [30]. Josiphos containing dendrimers have been constructed with arene (9), adamantyl (10) [31], and phosphazene (11,12) [32] cores and dendrimers containing up to 24 metallocene fragments [33] have been synthesized. The basic synthetic procedure is essentially identical for all the dendrimers.…”

“…While most of the dendrimers synthesized to date are organic molecules [3], there has been significant effort put forward towards the incorporation of other main group elements [4], and organometallic or transition metal entities and fragments [5,6]. This merging of fields hopes to combine the properties of the organometallic or transition metal species, such as catalytic [7][8][9], electrochemical, optical and magnetic properties, with the benefits generally attributed to dendrimers, such as site isolation [10,11], precise steric environments, recyclability [12] and possible cooperative effects. This topic has intrigued and excited numerous groups and has resulted in a myriad of new structures and architectures as well as applications for these species.…”

Synthesis of mesitylene-based polyamine dendrimer for functionalisation of single-walled carbon nanotubes

“…[1] Dendrimers are blossomed in the past decade as scaffolds for a wide variety of applications such as gene and drug delivery, catalysis, molecular recognition, in electrochrome molecular batteries, solar cells and liquid crystals. [2][3][4][5][6][7][8][9][10][11] Dendrimers can be constructed by following a divergent or convergent approach. The divergent mode of synthesis involves building up the molecules outwardly from a core, whereas attaching preformed dendrons of specific generation to the core is known as a convergent approach.…”