We then switched our focus to the more practical aqueous system. In aqueous solution (supporting electrolyte 0.2 M NaClO4), guest 1 is reversibly oxidized (Ru II/III) at 0.63 V vs NHE (Figure ). Additionally, we found that our systems are active in water, even without the addition of supporting electrolytes, in 0.5 M NH3 solution resulting in a pH of 11.3. An onset for AO in 0.5 M NH3 can be seen at 0.48 V vs NHE (Figure ). For guest 2, only a very weak redox peak at 0.70 V vs NHE was observable, which could again be a broad overlapping peak from RuII/III and RuIII/IV. However, the onset for ammonia oxidation was noticed at a similar potential for both guests (Figure ), though similar to the experiment in organic solvent, less pronounced for guest 2.