A helical peptide receptor for [60]fullerene.

Abstract

Two terminally blocked nonapeptides, each made up of six Aib residues, a Gly spacer and two L-Tyr residues in positions 2 and 8 (these are substituted in the side chain with either ferrocenoyl or methyl moieties), have been synthesized by solution methods and fully characterized. FT-IR absorption and two-dimensional NMR analyses indicate that a 3(10)-helical conformation is adopted by these rigid peptides in structure-supporting solvents. An X-ray diffraction investigation shows that the bis-L-Tyr(Me) nonapeptide in the crystal state is folded in a regular right-handed 3(10)-helical structure. As five amino acid units separate the two substituted L-Tyr residues in the peptide sequence, the two side chain moieties will-in solution-face each other after two complete turns of the ternary helix. By carrying out a detailed photophysical analysis, we have demonstrated that the electron-rich, hydrophobic and wide cavity generated by the nonapeptide template with two ferrocenoyloxybenzyl walls is able to host [60]fullerene. Further evidence for this superstructure has been provided in the gas phase by a mass spectrometric investigation.