Fullerenes metal macrocycles

Rubin, Y. Parker, T.C. Kahn S.I. Holliman, C.L. McElvany S.W. Precursors to endohedral metal fullerene complexes synthesis and x-ray structure of a flexible macrocyclic acetylenic cyclophane CgiH h- J. Am. Chem. Soc. 1996, 35(22), 5308-5309. 

The parent oxacalix[3] arenas show little ability to bind alkali metals,however, a range of quaternary ammonium cations are attracted to the symmetric cavity. Deprotonation of the phenol moieties allows them to bind to transition metals (scandium, titanium, vanadium, rhodium, molybdenum, gold, etc.), lanthanides (lutetium. yttrium, and lanthanum), and actinides (uranium as uranyl). Oxacalix[3]arenes derivatized on the lower rim can complex gallium, mercury, and alkali metals, including sodium, in a manner reminiscent of natural transmembrane cation filters. One major use was to purify crude samples of fullerenes. The pseudo-Cs symmetry of the macrocyclic cavity is complementary to threefold symmetry elements of Cgo. which binds preferentially in... 

Notably, this metal-mediated concept, namely, coordination of a fullerene-pyridine ligand by a macrocyclic r-system, is very general and has been successfully extended to zinc complexes of phthalocyanines, porphycenes and corrphycene macrocycles. Interestingly, the binding strength reveals a close resemblance to the oxidation potential of the macrocyclic s -system porphycene > porphyrin. 

The concept of porphyrins and metalloporphyrins (MPs) that recognize and surround in solution opened the way to a new research field, implementing the development of hosts for binding and trapping fullerenes. Transition metals trapped in porphyrin-like structures can also interact directly with the fullerene spheroids. Indeed, the association between these macrocyclic structures and fullerenes takes place even with free base porphyrins (widely used are tetraphenylporphyrins, TPP) and is an association of different interactions such as van der Waal, electrostatic, and charge transfer. ... 

Fullerene derivatives functionalized with pyridine or imidazole substituents can coordinate with several metal porphyrins, Pc, and Nc in solution by means of self-assembly. Such electron-rich macrocyclic dyes are good electron donors as they absorb light in the visible near-infrared (IR) region and exhibit a usable redox potential. 

Metal Coordination A different kind of recognition pattern has been developed following the same approach adopted by Sauvage et al., " governed by a tetrahedrally coordinated Cu(l) center (Figure 2.30). The position and the amount of the donor and the acceptor resulted in a drastic variation of the lifetimes of the CSS. Relatively low lifetimes of 1.17 ps were measured in the case of the rotaxane presenting two porphyrin stoppers and is linked to the macrocycle. In the case when two fullerene stoppers are on the thread and a porphyrine is on the macrocycle, the lifetime increased to 32 ps. ° ... 

Fullerenes are an allotropic form of carbon, consisting of pure carbon atoms. A well-known example is C60, which is shaped like a football, so metal ions and other active agents can be enclosed in the inner cavity. Furthermore, fullerenes themselves can act as a guest molecule in complexes with macrocyclic ligands such as cyclodextrins. 

In addition to metal coordination bonds, hydrogen bondings, electrostatics, and 7T-7T interactions, the attractive interaction between the curved r-surface of a fullerene and the flat rr-surface of a porphyrin was recently reported [8,9]. When the fullerene and the porphyrin were linked covalently in the single molecule (see 6), the two functions interacted with each other to form a supramolecular assembly in the solid state. In contrast to this divergent system, macrocycle 7 was prepared from the fused zinc porphyrins for the convergent interaction with specific guests. Since 7 had space to accommodate two fuUerenes, this kind of interaction operated well in the supramolecular assembly and moleciflar recognition systems. 

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