Theoretical Study on the Structure and Spectral Properties of Several Classical and Non-Classical C₇₆ Isomers and Their Newly Synthesized Derivatives

X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra, as well as the ground-state electronic/geometrical structures of the newly discovered two non-classical isomers C₂-C₇₆(NC2) and C₁-C₇₆(NC3) with their derivatives C₂-C₇₆(NC2)(CF₃)₁₄ and C₁-C₇₆(NC3)Cl₂₄, as well as the non-IPR(isolated pentagon rule) isomer C₁-^#17418C₇₆ with its embedded metal fullerene U@C₁-^#17418C₇₆ have been calculated at the density functional theory (DFT) level. The electronic structure after chlorination is significantly different in the simulated X-ray spectrum. Both XPS and NEXAFS spectra reflect obvious isomer dependence, indicating that the "fingerprint" in X-ray spectroscopy can provide an effective means for the identification of the above-mentioned fullerene isomers. Time-dependent DFT was used to simulate the ultraviolet-visible absorption spectrum of U@C₁-^#17418C₇₆. The calculated results are in good agreement with the experimental consequence. This work reveals that theoretically simulated X-ray and UV-vis spectroscopy techniques can provide valuable information to help researchers explore the electronic structure of fullerenes and the identification of isomers in future experimental and theoretical fields.