DFT study of interaction of acetylene and C70 fullerene molecules

• The C 2 H 2 and C 70 interaction leads to [2 + 1], [2 + 2], and [3 + 2] cycloadduct formation. • The chemical interaction is carried out with exothermic or endothermic effects. • The C 70 derivatives have both a closed-cage and an open-cage fullerene structure. • The interaction between C 2 H 2 and C 70 proceeds in several stages. The interaction between the C 70 fullerene and acetylene was investigated using DFT calculations (DFT/B3LYP/6–31G (d, p)). It is shown that the C 72 H 2 formation proceeds through sequential [2 + 1], [2 + 2], and [3 + 2] cycloaddition reactions. The [2 + 1] and [2 + 2] pathways lead to the formation of various isomers with closed- and open-cages due to the cleavage of the C–C bond in C 70 . Geometrical parameters, charge distribution, and formation energies of the fullerene-acetylene reactive complexes and the C 72 H 2 molecules were determined for eight different types of bonds in C 70 . Transition-state structures were also characterized. Cycloadduct formation via acetylene activation by C 70 requires high activation energies, ranging from 205.67 to 218.02 kJ/mol. In contrast, the [2 + 1] and [3 + 2] cycloadducts can transform to [2 + 2] cycloadduct with activation energies ranging from 4.55 to 37.59 kJ/mol, and high exothermic effect ranges from −217.11 to −302.75 kJ/mol. The [2 + 2] cycloadduct can transform to C 72 H 2 with an attached hydrogen atom and a –С СН fragment, which requires activation energies of 378.35 kJ/mol. The results elucidate the multi-step reaction mechanisms and energy profiles underlying acetylene addition to C 70 , providing theoretical insight into the reactivity and stability of fullerene derivatives and guidance for understanding fullerene-based chemical processes in catalysis, particularly in conversions of hydrocarbons, and in the design of novel carbon nanostructures.