A DFT Request for the Band Gap, NBO Analysis, and Global Reactivity of the Doped Metallofullerenes and their Complexes with H2 Molecules

In this theoretical report, we are focused on the substituent effects of titanium dopants on the band gap, NBO, and global reactivity of C20-nTin metallofullerenes (n = 1 - 5), at DFT. The C18Ti2-2 metallofullerene is found as the most stable analog with the highest band gap, in which carbon atoms are replaced by Ti dopants in the equatorial location, separately. The charge on carbon atoms of C20 is estimated roughly zero, while the high positive charge on the C16Ti4-2 surface prompts this metallofullerene for hydrogen storage. The positive charge on Ti heteroatoms and the negative charge on their adjacent C atoms implies that these sites can be able to be influenced more readily by nucleophilic and electrophilic reagents, correspondingly. The electronic transitions are usually classified according to the orbitals engaged or the involved specific parts of the metallofullerene. Common types of electronic transitions in organic compounds are “π–π*”, “n–π*” and “π* (acceptor) – π (donor)”. Fascinatingly, the charge transfer (CT) tack places via the suitable overlapping among σC―Ti bondingʼs orbital along with σ*C―Ti anti-bondingʼs orbital of C20-nTin metallofullerenes. For example, the NBO analysis of C19Ti1 metallofullerene points out higher CT energy of σC―Ti → σ*C―Ti (16.31 kcal/mol) with respect to σC―Ti → σ*C―C (0.63 kcal/mol). The reactivity of metallofullerenes can be affected by the number and topology of the substituted dopants. Based on these results we infer that metallofullerenes are a potential material for hydrogen storage with high capacity and the driving force for reactivity of them is the relief of π-curvature strain and leads sp2→sp3 hybridized atoms.