Molecular geometries, electronic properties, and vibrational spectroscopic studies of endohedral metallofullerenes TM@C24 and TM@C24H12 (TM = Cr, Mo, and W)

Molecular geometries, electronic properties, and vibrational spectroscopies of TM@C-24 and TM@C24H12 (TM = Cr, Mo, and W) in their different spin configurations have been systematically investigated with the hybrid DFT-(U)B3PW91 functional. The results show that the TM atoms bind over the pentagon ring inside C-24 cage, and they move gradually toward the center of C-24 cage along with the increasing atomic radii. The most stable Mo@C24H12 and W@C24H12 are in their spin-triplet states. The analyses of dissociation energy and energy gap reveal that TM@C-24 (TM = Cr, Mo, and W) and Cr@C24H12 are not only thermodynamically stable, but also considerably stable kinetically. Meanwhile, natural population analyses tell us that the two cages act as electron acceptors, and the transferred charge from the W atom to C-24 cage is the largest in the endohedral metallofullerenes. Additionally, the vibrational frequencies and active infrared intensities may be used as evidence to characterize these unknown species.