Chaining Up Fullerenes

Supramolecular polymers are chains of monomeric compounds that self-assemble through reversible interactions, such as hydrogen bonding or metal coordination. Now, a group led by Nazario Martín at Madrid's Complutense University has exploited π-π electronic interactions to assemble a supramolecular chain of C₆₀ molecules tethered together via a tetrathiafulvalene analog called exTTF (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200703049). Attached to one C₆₀, two exTTF molecules linked by a spacer group form a concave aromatic surface that recognizes the convex surface of a second C₆₀ with an attached exTTF system. The researchers observed chains (shown) of up to five repeat units by MALDI-TOF mass spectrometry. Molecular weight estimates from dynamic light-scattering experiments indicate that chains with up to 400 repeat units could be forming, although the largest structures might be due to oligomer aggregation, the researchers note. Electronically, exTTF is an electron donor, while C₆₀ is an electron acceptor. Thus, the polymers may be useful in optoelectronic devices, particularly in organic photovoltaic solar cells.