A study on the stability, chirality, and theoretical spectra of the heterofullerenes C69X (X = N, P, As, B, Si, Ge)

There are two chiral and three achiral C69X isomers possible. The achiral structures belong to the CS group of symmetry while the chiral ones possess no symmetry elements. The stability of all five C69X heterofullerenes for each of the X heteroatoms (X = N, P, As, B, Si, Ge) was determined at the (U)B3LYP/6-31G∗ level. The isomer population in an equilibrium mixture varies with the heteroatom type: the highest content of the chiral isomers was predicted for boron (92%) and nitrogen (47% plus 48%), while for the other heteroatoms studied the achiral isomers significantly dominate. For the chiral structures, four different sinister-rectus chirality measures, SRCM: pure geometrical, labeled, mass, and charge, were calculated by our CHIMEA program. We found that the labeled and mass chirality measures calculated for the two types of chiral isomers did correlate with each other. For each chiral C69X molecule, spectroscopic VCD, IR, Raman, and NMR characteristics are discussed and demonstrated for their possible use for future identification and distinction of the isomers.

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