FUNCTIONALISED FULLERENES

Topics that have formed the subjects of reviews this year include contemporary issues in electron transport research, dynamics of bimolecular photoelectron transfer reactions, photophysical properties of functionalised fullerene derivatives, carbon-carbon bond formation via radical ions, photoinduced electron transfer processes in ketone, aldehyde, and ester synthesis, photochemical reactions between arenenitriles and benzylic donors, photo-oxidation of conjugated dienes, photoredox reactions of aromatic nitro compounds, electron transfer-mediated photochemistry of some unsaturated nitrogen-containing compounds, reactions of 02( Ag), carbon dioxide activation by aza-macrocyclic complexes, and photochromism of chalcone derivatives. ... 

A large number of functionalised fullerenes have been reported. They are synthesised by chemical reactions at the double bonds of the ball to form anchors for further condensation with small or large molecules such as proteins, lipids, DNA etc. They find applications in a variety of industries including dmgs and pharmaceutical industries and in medicine. They are of nano size, can circulate in the animal s body and can be used to deliver substances to targeted tissues. A few of these are commercially available in chemical catalognes and some are described here to show how fullerenes can be made to react with reagents. 

Preparation of mono-adducts of fullerene - for studies on electrostatic interactions - was undertaken by cyclopropanation of fullerene with appropriately functionalised malonic esters 1 (Bingel reaction) to form 2. Coupling with the tert-butyl protected oligoamide-amino-dendron 3 and subsequent hydrolysis lead to the water-soluble fullerene dendron 5, which can carry up to nine negative charges after depro to nation. After association with the zinc complex of cytochrome C, photoinduced electron transfer (PET) from the redox protein to the fullerene can be accomplished, which was studied by fluorescence spectroscopy. 

C76 fullerene [135113-15-4] M 912.85, melts above 350". It is now available commercially. After the sequential removal of and C70 fullerenes from soot extracts (see above) on gel permeation columns (e.g. Buckyclutcher 1 column), C76 and higher fullerenes are obtained. These are further separated on a Tridait-TriDNP functionalised silica column. After two HPLC runs on a Cjg reverse phase (Vydac 201 TP C,g) column and eluting with 1 1 MeCN/toluene, pure C76 fuUerene is obtained. The identity is confirmed by HPLC/GPC system with Waters 600E UV/VIS detection, mass and NMR spectroscopy. [Seleque et al. In Kadish and Ruoff (Eds) Fullerenes Recent Advances in the Chemistry and Physics of Fullerenes and Related Mfltena/i The Electrochemical Soc. Inc, Pennington, NJ, 1994 ISBN 1566770823, Diederich Whetten Acc Chem Res 25 119 1992, Diederich et al. Science 254 1768 1991.]... 

Synthetic ion-exchange resins [213], silica-based exchangers [214] and activated alumina [209] have been most commonly used other materials used include cross-linked dextran gel (Sephadex) [215], fullerenes (especially Cis and Q,y)[216], polyurethane foam [217], PTFE turnings [218] or fibres [219], cigarette filters [220], functionalised cellulose [221], activated carbon [222], grape bagasse [223], rice husks [224] and bioorganisms (Saccharomyces cerevisiae) [225]. 

Regarding fullerene chemistry, whereas the covalent functionalisation of buckminsterfiillerene Ceo has seen dramatic development, the supramolecular aspects of its chemistry have not been explored to the same extent. In contrast to covalent bonds, the formation of H-bonds is reversible and their strength depends on the chemical environment, such as the solvent or temperature. This important difference has been skillfully used in the preparation of a variety of reversible donor-acceptor dyads. 

Fowler, R W., 8c Heine, T. (2001). Stabilisation of pentagon adjacencies in the lower fullerenes by functionalisation. Journal of the Chemical Society, Perkin Transactions 2,487-490. 

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