The second isomer of Pr@C-82 (Pr@C-82-II) has been isolated by a two-step HPLC method, separately from the known major isomer (Pr@C-82-I). Visible and near-IR absorption spectra, as well as cyclic and differential pulse voltammograms show that the characteristic features of Pr@C-82-II are significantly different from those of Pr@C-82-I. The absorption peaks of Pr@C-82-II have blue-shifts and the redox potentials have negative shifts, relative to those of Pr@C-82-I. Chemical derivatization of both isomers with disilirane have also been achieved.