Molecular structure, electronic property and vibrational spectroscopy of C24–glycine and Gd@C24–glycine complexes

Structure, electronic property and vibrational spectroscopy of C24–glycine and Gd@C24–glycine were systematically explored using the hybrid DFT-B3LYP functional. The interaction between empty C24 cage and the smallest amino acid (glycine) was also investigated. It was found that the glycine molecule is energetically favorable to interact with the Mid-site on the C24 cage through the amino nitrogen active site, rather than Top-site. The endohedral Gd atom increases the volume of the cage by around 6.7–9.8%. Analysis of frontier molecular orbitals reveals that the Gd@C24–glycine has the low-kinetic stability, being consistent with its thermodynamic property reflected by dissociation energy. We also see that the VIE and VEA of empty C24 cage are slightly affected by absorbed glycine and endohedral Gd atom. Additionally, the assignments of simulated IR spectra are explored. The work may provide a theoretical reference for further application related structurally to potential antitumour activity.

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► The glycine is energetically favorable to interact with Mid-site on the D6–C24 cage, not Top-site.
► The endohedral Gd atom increases the volume of the cage (6.7–9.8%) in Gd@C24–glycine.
► The Gd@C24–glycine has the low kinetic and thermodynamic stabilities.
► VIP and VEA of empty C24 cage are slightly affected by glycine and endohedral Gd atom.
► The theoretical IR spectra of studied complexes were simulated by DFT calculations.