Fullerene complexes characterization

Occurrence of Fully Characterized Metal-Bound Fullerene Complexes... 

In contrast to the great variety of known organic adducts, there is a relative paucity of metal-containing fullerene complexes. Tables III and IV list (in yearly order of appearance in the literature) all the fully characterized (6, 7) and many of the known [Pg.6]

The heteroatom cy clopentadienyl analog 1,4,2-P2 SbC2 Bu 2 has been coordinated to Tl(l) via equation (2), producing zigzag polymer (2). Thallium coordination has played an important role in crystallographic characterization of metal-fullerene complexes, providing the first structurally characterized pentahapto metal complexes of Ceo (3) and C70 (4). The key to the formation of these monothallium(l) compounds was the arylation of the fullerenes. Methylated Ceo forms a thallium complex as well. ... 

Fully Characterized tt-Bonded Metal-Fullerene Complexes"... 

This review covers all organometallic complexes of Sc, Y and the lanthanides reported in the year 2000 and their reactions. Endohedral fullerene complexes of the lanthanides have, as usual, been excluded. Highlights this year include striking reports of lanthanides in non-classical oxidation states (Sections 3.2 and 5), a remarkable reversible dinitrogen activation described in Section 3.9.2 and evidence for the existence of the divalent hydrides LnH2(THF)2 (Ln = Sm, Yb) (Section 3.10). In addition Evans has assessed the utility of electrospray mass spectrometry for the characterization of organolathanides. The results are promising and the spectra and dissociation patterns show sensitivity to the metal and its oxidation state. ... 

Crystal structures of a few fullerenes containing endohedral atoms have been recently solved (apart from the noble gas trapping Kr C60,22a the metal atoms containing Sc3 N C78,22b Sc3 N C80 and Sc2 ErN C80>22c Y C82,22d Sc C82,22e Er2 C82,22f Sc3 Cs2,228 Sc2 C84,22h Sc2 C2 C84,221), but unfortunately their electrochemical behaviour is not known. Electrochemical information is also limited for those endohedral complexes which lack definitive structural characterization.23... 

This review describes the preparation, characterization, and properties of all nonpolymeric complexes that contain a metal removed from the fullerene also are included. The article does not cover the essentially ionic fullerides MmC (4) or the endohedral metallofullerenes MmC (8), which have been reviewed previously. The extended fullerenes, or so-called carbon nanotubes, which have hollow centers and can be filled with metal salts, also are not discussed. The majority of complexes involve 7r-bonds and, apart from alkyl lithium fullerides, the potentially useful synthetic area of o- complexes has not been explored. Table I shows the occurrence of metal-bound adducts across the periodic table. 

It is a considerable challenge to isolate a pure adduct. One of the unique features of fullerene chemistry is the large number of products that sometimes result from addition of even one mole eqivalent of reagent. Owing to its relatively high abundance, most fully characterized complexes are for C60, but the behavior of higher fullerenes is broadly similar. The availability of only small amounts of higher fullerenes, coupled with the inequivalency of some of the double bonds, introduces additional complications. 

We now present an exhaustive survey of all the fully characterized metal ir or a complexes reported to date. The survey also includes adducts where the metal is one bond removed from the fullerene, such as 60 2 8 2(4- 5 4 2 and C60S2Fe2(CO)6. Adducts in which the metal is bound at a more distant site on the organic side chain are not discussed. 

Although the tt complexes have not yet found any practical uses, they have proved helpful in structural characterization, as well as providing some insight into the dynamical behavior of fullerenes. The a- complexes are a relatively unexplored area, but where they have been prepared, they are useful intermediates in the preparation of organic fullerene adducts. 

NMR spectroscopy has been an extraordinary important technique for structure determination of hydrogenated fullerenes ever since the first synthesis of hydrogenated fullerenes almost two decades ago. During this time, technical advances have pushed the limits regarding both sensitivity and spectral resolution. Also, sophisticated 2D NMR experiments have been implemented more and more frequently in recent years. Consequently, NMR spectroscopy has now been used to successfully characterize complex hydrogenated fullerenes whose structure for a long time... 

The complex between ( )-37 and KPF6 was characterized by X-ray crystal-structure analysis, which confirmed the close tangential orientation of the ionophore moiety with respect to the fullerene surface, which had been predicted by computer modeling (Figure 15). 

In bulk heterojunction solar cells, the metal/semiconductor interface is even more complex. Now the metal comes into contact with two semiconductors, one p-type (typically the polymer) and one n-type (typically the fullerene) semiconductor. A classical electrical characterization technique for studying the occurrence of charged states in the bulk or at the interface of a solar cell is admittance spectroscopy. If a solar cell is considered as a capacitor with capacitance C, the complex admittance Y is given by... 

The nanotubular cavities (mean diameter 12.4 A) were found to be effective hosts for C6o molecules (van der Waals radius 10.3 A), and were capable of solubilising Ceo in solvents such as chloroform, where the fullerene has poor solubility. UV-vis, CD, 13C-NMR and molecular modelling were used to characterize this NDI nano-tube-C6o host-guest complex [26]. 

It must be emphasized that in fact a very similar situation characterizes experimental investigations, since very different experimental techniques are employed, and different questions are asked, when investigating simple diatomics on the one hand and complex systems, such as chlorophyl, proteins, fullerenes, etc. on the other. Even if one could resolve and measure, for instance, all the individual ro-vibrational lines in the electronic spectra of large systems involving, say, more than 50 carbon atoms, the usefulness of such information is debatable. Likewise, our theoretical inquiries call for different models, approximations and techniques when handling different types of problems. 

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