This intrachain electron transfer is not present in the other double protonated structure, namely Double-2. Due to the different positioning of the second proton with respect to the middle of donor unit D4 (green number 2 in Fig. ), a potential overlap of induced charges is avoided. The DOS of the optimized Double-2 still features a broken-spin symmetry, but the orbitals induced by the protons are similar to the orbitals of the single protonated structures Proton-1 and Proton-2, i.e. the additional proton induces a polaron close to its position situated on the left side of donor unit D4. Moreover, the charge distribution is identical to the charge distribution expected from the results for single protonated structures (Fig. , blue bars) and the IVM induced by the polaron has similar frequency as for Proton-1 (cf. Fig. and Fig. ).