Highly Hydroxylated Buckminsterfullerene Complexes with an Endohedral Iodide Anion

The properties of the complexes I^-@C₆₀(OH)₂₀ and I^-@C₆₀(OH)₃₀ have been determined using the quantum chemical DFT PBE0 method to assess the possibility of synthesis of highly hydroxylated fullerene endo-iodides for the use in radiotherapy of different organs. The arrangement of the hydroxyl groups corresponds to the location of halogen atoms in (D_5d)-C₆₀F₂₀ and (D_3d)-C₆₀Cl₃₀. Negative-charged iodine is localized in the center of the fullerene cavity and has no significant influence on the IR spectra of hydroxylated fullerenes. The exothermic effect of iodide anion encapsulation in C₆₀(OH)_n (0.33 eV at n = 20; 0.03 eV at n = 30) is smaller than in C₆₀ (0.78 eV). The energies of the lower excited singlet states computed by the TD DFT method for I^-@C₆₀(OH)_n (2.11 eV at n = 20; 1.77 eV at n = 30) are larger than those for I^-@C₆₀ (1.36 eV). They indicate a low reactivity, making it possible to synthesize such complexes for medical use.