The Raman frequencies of the polyyne dumbbells and rotaxanes are listed in Table , and plotted against the number of triple bonds, n, for the Mb rotaxanes in Fig. . The presence of a threaded macrocycle has a negligible effect on the Raman frequency. This contrasts with the situation when a polyyne is encapsulated inside a double-walled carbon nanotube, where the Raman frequency is governed by the chirality of the inner tube and reduces with decreasing inner tube diameter . The reduction in frequency of 177 cm -1 from C12•Mb (ν = 2077 cm -1 )