The higher oxides of carbon C8nO2n (n = 3-5): synthesis, characterization, and x-ray crystal structure. Formation of cyclo[n]carbon ions Cn+ (n = 18, 24), Cn- (n = 18, 24, 30), and higher carbon ions including C60+ in laser desorption Fourier transform mass spectrometric experiments

The new higher oxides of carbon 1 (C 24 O 6 ), 2 (C 32 O 8 ), and 3 (C 40 O 10 ) have been prepared from the macrocyclic ketals 5-7 and characterized as stable colored solids. The electronic absorption spectra of the carbon oxides 1-3 differ from those of the ketals 5-7. The absorption bands of 1-3 are broader and shifted to longer wavelength. The X-ray crystal structure of oxide 1 has been determined, showing that 1 is planar, with bent diyne units. The laser desorption Fourier transform mass spectra of 1 and 2 show a remarkable ease of successive losses of two CO molecules to give C 18 and C 24 ions, respectively, in both positive and negative modes. The C 30 ion formed by fragmentation of oxide 3 is considerably less stable than the smaller homologues and is only observed in the negative ion mode. In the positive ion spectra recorded at low desorption laser power, ions corresponding to the dimers of the cyclocarbons are observed. In addition, higher carbon ions are formed with C 60 + being abundant in the spectra obtained from all three carbon oxides