Supramolecular Chemistry of Carbon Nanotubes

Figure 8.10 Soluble supramolecular complexes of carbon nanotubes, 0.01 M Na2S04, aqueous solution. Scan rate = 0.1 V/s T— 25°C working electrode is Pt disc (r — 0.05 cm). Potentials measured versus silver quasi-reference electrode (approximately —0.05 V versus SCE). Ref. 121, Reproduced by permission of the Royal Society of Chemistry.

First described in the literature in 1814, the blue reaction of iodine with starch is the best-known example of a polymerization process induced by supramolecular stabilization. Structural studies indicate that amylose (the linear fraction of starch) forms a helix with six glucose residues per turn to include guest iodine molecules. Inside this helix, iodine molecules form a polymeric chain with a periodicity of 3.1 A, which is much shorter than the nonbonded distance between iodine atoms (4.3 A) but greater than the single I-I bond distance (2.7 A). The amylose-iodine reaction is widely used in analytical chemistry and was utilized for the solubilization and purification of carbon nanotubes. 

The chapter Supramolecular Information/Programming from a Boolean Perspective, Concepts delves deeper into the reversible covalent bond toolbox. The equilibration of these strong covalent bonds, often referred to as dynamic covalent chemistry, is kineticaUy slower in comparison to weaker noncovalent interactions and often requires a catalyst. An extreme example might also include the formation of carbon nanotubes and fullerenes. While not spontaneous at room temperature, carbon vapor at high temperature does assemble to form these intricate and beautiful stractures. 

L. Gu, F. Lu, P. G. Luo, et al., Functionahzed carbon nanotubes for bioapplications, in The Supramolecular Chemistry of Organic-Inorganic Hybrid Materials, eds K. Rurack and R. Martmez-Mdnez, John Wiley Sons, Inc., Hoboken, NJ, 2010, pp. 197-233. 

Martin N. Nierengarten, J. F. Supramolecular Chemistry of Fullerenes and Carbon Nanotubes-, Wiley-VCH Verlag GmBH Weinheim,... 

Heterocyclic Supramolecular Chemistry of Fullerenes and Carbon Nanotubes... 

The final chapter, Heterocyclic Supramolecular Chemistry of Fullerenes and Carbon Nanotubes by N. Komatsu presents an extremely unique review that focuses on the noncovalent chemistry of fullerenes and carbon nanotubes with nitrogen- and/or oxygen-containing heterocyclic molecules such as porphyrin, DNA, protein, peptide, and carbohydrate. Not only exohedral but also endohedral fimctionahzation is reviewed, because the above guest molecules can interact with both faces of the carbon nanotubes. The hurdles in structural separation, nanofabrication, and bioappHcations of carbon nanotubes will hopefully be addressed by the supramolecular strategy. 

Like the currently popular area, called nanoscience , the field of supramolecular chemistry has rather hazy boundaries. Indeed, both areas now share much common ground in terms of the types of systems that are considered. From the beginning, electrochemistry, which provides a powerful complement to spectroscopic techniques, has played an important role in characterizing such systems and this very useful book goes considerably beyond the volume on this same topic by Kaifer and Gomez-Kaifer that was published about 10 years ago. Some of the classic supramolecular chemistry topics such as rotaxanes, catenanes, host-guest interactions, dendrimers, and self-assembled monolayers remain, but now with important extensions into the realms of fullerenes, carbon nanotubes, and biomolecules, like DNA. 

---