Unmasking of the [5]rotaxane mC68•(Mb)4 using MMPP (120 equiv.) gave the polyyne [5]rotaxane C68•(Mb)4 in 23% yield, after purification by silica gel chromatography and washing with ethanol, whereas this compound could not be prepared by unmasking mC68•(Mb)4 with mCPBA. This polyyne [5]rotaxane is an orange-red solid, and it is stable in solution over several days on storing at -20 °C, but some decomposition is observed during chromatography. The C68 polyyne chain of this [5]rotaxane makes it longer than any previously reported polyyne . It was fully characterized by 1 H NMR, UV-vis and Raman spectroscopy and high-resolution mass spectrometry. We also prepared C68•(Ma)4 but this [5]rotaxane is less stable than the version with the smaller macrocycle, which prevented characterization by NMR spectroscopy. UV-vis and Raman spectra. Polyynes exhibit characteristic electronic absorption bands, with sharp vibronic fine structure, which shift to longer wavelength as the length of the polyyne chain increases . The absorption maxima (λmax) of the polyyne dumbbells and polyyne rotaxanes synthesized in this study are summarized in Table . The presence of threaded macrocycles has little effect on the absorption spectra, and the λmax values of the naked polyyne dumbbells are similar to those of the corresponding polyyne rotaxanes, although the spectra of the rotaxanes are red-shifted by 3-9 nm, due to the different solvent environment around the threaded polyyne chain , while the type of macrocycle (Ma vs. Mb) has no significant effect on the spectra. The variation in λmax with the number of triple bonds, n, is plotted in Fig.