Hydrogen positions were assumed, C-H 0.95 A, and repositioned once near the end of refinement. Structure solved using MULTAN 8 8. j-asaic f A m 3r Ahm-Chem' Soc. D. ? S^^' Soc-v. 115-• v .,c m. ooc u 1 1 c Supplementary material, P-2524 M arder 15 page 3 N3 C4 05 CH CIO C8 N1 C9 C7 C3 C12 C6 K2 Cl z ClspL-oL '^]/k jO s lc M s U Figure 1: An ORTEP drawing of the molecule with 50% probability elipsoids showing the numbering system. Hydrogen atoms are drawn as circles of arbitrary small size.

The oxidation and rereduction of the redox liquids para-N,N,N′,N′-tetrahexylphenylenediamine (THPD) and para-N,N,N′-trihexylphenylenediamine (TriHPD) associated with anion and proton insertion and expulsion are studied as a function of the proton concentration in aqueous NaClO 4 electrolyte. Voltammetric, in situ UV/vis-spectroelectrochemical, and quartz crystal microbalance techniques are employed. The biphasic acidbase equilibria of the redox liquids involving protonation and simultaneous anion transfer from the aqueous phase are shown to exhibit only small deviation from ideal behavior and well-defined biphasic dissociation constants, pK A,biphasic have been determined. However, the protonation of the bulk redox liquids is shown to be dominated by intermolecular rather than intramolecular factors. In particular, the ability of THPD to undergo bulk protonation by HClO 4 is higher (pK A2,biphasic ) 5.1) compared to that of TriHPD (pK A2,biphasic ) 3.9); this is opposite to the behavior predicted on the basis of the estimated values for the aqueous protonation equilibrium constants, pK A2 ) 7.5 ( 0.5 and pK A2 ) 8.8 ( 0.5 for THPD and TriHPD, respectively. Further, the electrochemically driven deprotonation occurs irrespective of protonation constants at essentially the same potential for both materials. The three-phase junction electrode|redox liquid|aqueous electrolyte for the initiation of the anion and proton insertion-electrochemical reactions is shown to be the key to processes observed for neutral redox liquids, whereas ionic redox liquids show reactivity independent of the three-phase junction due to sufficient ionic bulk conductivity.

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