Theoretical study of C36 and O@C36 fullerene isomers with (C1, C2, Cs, D2, and D3h) symmetries: Geometry optimization, electrical properties, and spectroscopic analysis

In this study, we conducted a theoretical analysis of specific C36 and O@C36 Fullerene isomers, namely, those with (D3h, C1, Cs, C2, and D2) symmetries, in the gaseous phase using the density functional theory method at B3LYP/6-31G* level. We studied geometry optimizations, relative stability, atomization energies, Fermi energy, energy gap, electronic properties, electric dipole moment, polarizabilities, and thermodynamic analysis, along with IR and NMR spectra. Consistently, our findings revealed distinct properties and characteristics among different C36 fullerene isomers. The energetic order of C36 fullerene isomers was established as C36–D3h < C36–C1 < C36–Cs < C36–C2 < C36–D2, a trend unaffected by the encapsulation of oxygen. Notably, the D2 isomer displayed the smallest energy gap, indicating higher electrical conductivity compared to other isomers, while it exhibited the largest gap after encapsulation. Furthermore, we observed that the C1 (D2) isomer exhibited the largest (smallest) electric dipole moment among the studied C36 isomers, whereas the C2 (D2) isomer demonstrated the largest electric dipole moment among the O@C36 isomers studied. The encapsulation of oxygen in C36 isomers influenced their properties, including alterations in electronic properties, IR, and NMR chemical shifts. A detailed analysis of Basis Set Superposition Error (BSSE) corrections showed the tininess of their impact on the analyzed observables, such that uncorrected and BSSE-corrected calculations led to nearly identical results, confirming the robustness and reliability of the B3LYP/6-31G* approach used in this work and, eventually, in other large and rigid fullerenes systems.