An Open-Cage Fullerene That Mimics the C60 H10 (5,5)-Carbon Nanotube Endcap to Host Acetylene and Hydrogen Cyanide Molecules.

Treatment of the open-cage fullerene C63 H4 NO2 (Ph)2 (Py)(N2 C6 H4 ) (1) with methanol at 150 °C results in an orifice-enlargement reaction to give C69 H8 NO(CO2 Me)(Ph)(Py)(N2 C6 H4 ) (2). The overall yield from C60 to isolated 2 is 6.1 % (four steps). Compound 2 contains a 24-membered elliptic orifice that spans 8.45 Å along the major axis and 6.37 Å along the minor axis. The skeleton of 2 resembles the hypothetic C60 H10 (5,5)-carbon nanotube endcap. The cup-shaped structure of 2 is able to include water, hydrogen cyanide, and acetylene, forming H2 O@2, HCN@2, and C2 H2 @2, respectively. The molecular structures of H2 O@2 and HCN@2 have been determined by X-ray crystallography. The 1 H NMR spectra reveal substantial upfield shifts for the endohedral species, such as δ=-10.30 (for H2 O), -2.74 and -14.26 (for C2 H2 ), and -1.22 ppm (for HCN), owing to the strong shielding effects of the fullerene cage.