Catalysts supramolecular anchoring

Fig-1 Schematic presentation of supramolecular anchoring of catalysts to dendritic... 

Fig. 7 The concept of supramolecular anchoring of catalysts to dendritic binding sites immobilized on silica (A) and the binding motif based on hydrogen bonding (HB) that has been used...

Abstract Artificial metalloenzymes can be created by incorporating an active metal catalyst precursor in a macromolecular host. When considering such artificial metalloenzymes, the first point to address is how to localize the active metal moiety within the protein scaffold. Although a covalent anchoring strategy may seem most attractive at first, supramolecular anchoring strategy has proven most successful thus far. 

Ribaudo F, van Leeuwen PWNM, Reek JNH (2006) Supramolecular Dendritic Catalysis Noncovalent Catalyst Anchoring to Fimctionalized Dendrimers. 20 39-59 Richmond TG (1999) Metal Reagents for Activation and Functionalization of Carbon-Fluorine Bonds. 3 243-269... 

Supramolecular chemistry also provides new tools for catalyst anchoring. We have shown that catalysts can be noncovalently attached to various soluble and insoluble supports, affording recyclable catalysts. Interestingly, the reversible nature of the noncovalent bond gives rise to new opportunities. In the first instance, we foresee an important role for supramolecular bidentate ligands in combinatorial catalysis - but as a consequence of the entirely new properties many new applications are envisioned. We look forward to new developments and results in this exciting emerging area of supramolecular catalysis. 

Fig. 4 The first supramolecular dendritic catalyst in which 32 phosphine ligands are noncovalently anchored to the functionalized dendrimer by hydrogen bonds and ionic interactions...

Supramolecular Dendritic Catalysis Noncovalent Catalyst Anchoring to Functionalized Dendrimers... 

Immobilization of active species by supramolecular interactions has a number of advantages. These include (a) new opportunities to apply catalysts after their anchoring to solids, (b) facilitated separation of spent and intact catalysts, and (c) exchange of the active metal complex on the surface. 

The guanidinium unit plays a crucial role in the activity of some enzymes such as staphylococcal nuclease [23] and has been used as an activating and/or anchoring group in the design of supramolecular catalysts [24-28]. Artificial phosphodiesterases 27 30 were developed by introducing from two to four guanidinium units at the upper rim of a cone calix[4]arene scaffold [26]. 

---