Electronic structures and stabilities of endohedral metallofullerenes TM@C34 using DFT approach

Theoretical study of the electronic structure using, Density Functional Theory (DFT) calculations at the B3PW91/6-31G (d) level of theory have been employed to the TM@C34 (TM =Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) in order to investigate the geometries, electronic structures, binding energies, linear polarizability ⟨Δ𝛼⟩, first order hyperpolarizability ⟨𝛽⟩, natural bonding orbital (NBO), was studied based on the C34 fullerene. The results found that the most stable structure is e(C2). Minimal energy structures of each endohedral metallofullerene were obtained. Hybridizations were found between the Ti, V, Cr, Fe, Co, and Ni, 3d valence orbitals and the C34 cage orbitals, while none was found between the Mn and Cu orbitals and the C34 cage orbitals. These findings were obtained with the preferential position of the metal atom inside the fullerene cage, i.e.  these results are found suitable for the metal Mn and Cu orbitals present inside the  fullerene cage. Natural bonding orbital (NBO) shows that the charges always transfer from the TM atoms to the C34 cage. In going from isolated TM atom to TM@C34, the occupation of the 4s orbital is strongly reduced. The introduction to TM to the empty C34 leads to more active NLO performance. The TM@C34 (TM =Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) interactions are characterized in terms of several theoretical parameters such as density of states (DOS), molecular electrostatic potentials (MEPs), nonlinear optical (NLO) properties and  electrophilicity and thermodynamic properties were also performed at B3PW91/6-31G (d) level of theory.