Solubility of fullerenes

Some fullerene structures are not soluble because they have a small band gap between the ground and excited states. These include the small fullerenes {{chem|C|28}}, {{chem|C|36}} and {{chem|C|50}}. The {{chem|C|72}} structure is also in this class, but the endohedral version with a trapped lanthanide-group atom is soluble due to the interaction of the metal atom and the electronic states of the fullerene. Researchers had originally been puzzled by {{chem|C|72}} being absent in fullerene plasma-generated soot extract, but found in endohedral samples. Small band gap fullerenes are highly reactive and bind to other fullerenes or to soot particles.

Solubility of {{chem|C|60}} in some solvents shows unusual behaviour due to existence of solvate phases (analogues of crystallohydrates). For example, solubility of {{chem|C|60}} in benzene solution shows maximum at about 313 K. Crystallization from benzene solution at temperatures below maximum results in formation of triclinic solid solvate with four benzene molecules {{chem|C|60}}·4{{chem|C|6}}H₆ which is rather unstable in air. Out of solution, this structure decomposes into usual face-centered cubic (fcc) {{chem|C|60}} in few minutes' time. At temperatures above solubility maximum the solvate is not stable even when immersed in saturated solution and melts with formation of fcc {{chem|C|60}}. Crystallization at temperatures above the solubility maximum results in formation of pure fcc {{chem|C|60}}. Millimeter-sized crystals of {{chem|C|60}} and {{chem|C|70}} can be grown from solution both for solvates and for pure fullerenes.

The following are some solubility values for {{chem|C|60}} and {{chem|C|70}} from the literature, in grams per liter.

• Fullerene chemistry

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Category:Fullerenes

Category:Solutions