If 9H is the proton donor, the switching process is not coupled to the decarboxylation reaction; the catenane simply remains protonated until the system runs out of 9H (Figure ). If the system is chemostated to a steady state (i.e., [9H], [10H] and [CO2] are held constant), there is no net flux between 8 and 8H + . Conversely, if 8H + is the proton donor (Figure ), the reaction network is cyclic and there is net flux at steady state; the molecular switch moves back and forth between the co-conformational states, 8 and 8H + once for each decarboxylation event and thus the switch could be said to be operating autonomously and continuously in the presence of excess 9H. In fact, both pathways may contribute, and their relative importance could depend on the reaction conditions. Similarly, Cl3CCO2H (12H), which undergoes a base catalyzed decarboxylation to give CHCl3 (13H), has been used to operate catenane (e.g., 11) and rotaxane molecular motors. Although the motion superficially appears to be coupled to the conversion of 12H to 13H, we must analyze the system to understand how its behavior should be interpreted. In this case, the conclusion is unambiguous; because addition of 12H results in a single cycle of operationthe ring first moves clockwise from the triazolium station past the acid labile hydrazone "gate" to the protonated ammonium station, and then when the pH rises it returns to the triazolium station past the base labile disulfide "gate"catenane 11 operates by an energy ratchet mechanism.