Comparison of the IP and EA values of TBAP, TPhP and TPyP when modelled as isolated molecules immersed in water. Solution potentials for the reduction of protons to hydrogen and oxidation of ascorbic acid at pH 2.6, the likely pH of a 0.1 M ascorbic acid solution (left), and reduction of protons and oxidation of triethylamine at pH 11.5, the likely pH of a triethylamine solution, taken from the literature. Fig. shows the predicted IP and EA values of TBAP and TPhP relative to those of the solution potentials relevant to the use of ascorbic acid as a hole scavenger and those of TPhP and TPyP for when using triethylamine instead. The two scenarios differ not only in scavenger but also in the pH of the resulting solution and hence the proton reduction potential is also different. All materials are predicted to have a very large driving force for proton reduction and reasonable driving force for the overall oxidation of ascorbic acid and triethylamine respectively. However, while TBAP and TPyP also have a small driving force for the intermediate oxidation step, this is predicted to be not true for TPhP. In the case of TPhP, the one-hole oxidation of ascorbic acid/triethylamine could thus act as an as an effective thermodynamic barrier to overall oxidation, which might be a contributing factor to the lower hydrogen evolution rates observed for TPhP when compared with TBAP/TPyP. . demonstrates that our periodic DFT calculation reproduces the lattice parameters of the desolvated TBAP-α well. The slight contraction of the DFT structure relative to the experimental structure is probably in part related to the fact that the experimental structure solved from diffraction data obtained at room temperature. ), and the analogous tetramer case (IV, 4C+). Solution potentials for the reduction of protons and oxidation of ascorbic acid at pH 2.6, the likely pH of a 0.1 M ascorbic acid solution, taken from the literature. Fig. shows that the effect of packing on the predicted potentials of TBAP-α is very small, or at least when we make the assumption that the pores contain significant amounts of water. For all structural models it is predicted that there is a very large driving force for proton reduction and a reasonable driving force for the overall oxidation of ascorbic acid (A/H2A). The intermediate one-hole oxidation of ascorbic acid (HA*/H2A), which could act as an effective thermodynamic barrier to overall oxidation, is also in all cases predicted to be exergonic, though only by a small amount.