Comparison of the synthetic IR spectra of Fe₁₂–C₁₀H₂ (M_s = 37 and 39) with its charged state ﹩{\mathrm{Fe}}_{12}^{+}﹩–C₁₀H₂ (M_s = 36 and 38). The optimized structures are shown as insets. Brown spheres correspond to Fe, gray to C, and light gray to H. Blue arrows mark the peaks associated with the IR-active CCH/CCC bending modes. The charged state does not dramatically alter the structures or IR spectra.