Endohedral pnicogen and triel bonds in doped C60 fullerenes

Abstract

Similar to C₆₀, there are some heterofullerenes that have the right combination of size and stability to serve as the host for a large variety of atoms and molecules. In this context, the present study theoretically investigates the endohedral complexes of doped C₆₀ fullerenes, C₃₀X₁₅Y₁₅ (X = B, Al and Y = N, P) with H_nYF_3−n (Y = N, P and n = 1, 2) guest molecules. First, the effects of substitutional co-doping of C₆₀ with B/N, B/P, Al/N, and Al/P have been systematically studied. Among the heterofullerenes that we have considered, C₃₀B₁₅N₁₅ is thermodynamically the most stable C₆₀ analogue followed by C₃₀Al₁₅N₁₅ and the phosphorus-containing cages are unstable. Then we have analyzed the distribution of the Laplacian of electron density to show that these heterofullerenes are potentially able to form several lump–hole interactions with the encapsulated molecules. In the second part, the incorporation of H_nYF_3−n guest molecules inside the two stable hosts, C₃₀B₁₅N₁₅ and C₃₀Al₁₅N₁₅, has been investigated. Eight minimum energy structures have been found involving pnicogen and triel bonds. The interaction energies, equilibrium geometries, and harmonic vibrational frequencies of the endohedral complexes have been calculated. The results indicate that all the guest molecules are stabilized inside the cages. The most pronounce interaction energy (−31.88 kcal mol⁻¹) is observed for H₂NF@C₃₀B₁₅N₁₅. Analysis of natural bond orbitals reveals the significant role of orbital interactions within the investigated endohedral complexes. The charge transfer energies are found to be up to 58.06 and 47.10 kcal mol⁻¹ in H_nYF_3−n@C₃₀Al₁₅N₁₅ and H_nYF_3−n@C₃₀B₁₅N₁₅, respectively.