Structural and electrochemical data for 2 and 3.

	2	3
O⋯N distance (Å)	2.57a, 2.57b	2.61a, 2.58b
N⋯N distance (Å)	2.92a, 2.84b	2.83a, 2.83b
Phenol-benzimidazole torsional angle (°)	3.4a, 2.4b	1.3a, 3.3b
Benzimidazole-imine linkage torsional angle (°)	1.9a, 0.1b	3.6a, 0.6b
δ NH (ppm)c	11.84	11.97
δ OH (ppm)c	13.30	13.14
Calculated E1/2 (V vs. SCE)d	0.95e	0.85
Experimental E1/2 (V vs. SCE)f	0.95	0.87
ΔEp (mV)g	130	64
i c/iag	0.97	0.91

^aDetermined by X-ray diffraction measurements.

^bDetermined by DFT calculations.

^{c 1}H NMR data in CDCl₃.

^dEach computed redox potential assumes the maximum number of intramolecular proton transfers. The redox potentials corresponding to the intermediate proton transfer process (E1PT) are given in Table S13.

^eThe potential for 2 in CH₂Cl₂ was used as the reference for all calculated potentials associated with an E2PT product, and therefore it agrees with the experimental value by construction.

^fThe potential of the pseudoreference electrode was determined using the ferrocenium/ferrocene redox couple as an internal standard and adjusting to the saturated calomel electrode (SCE) scale (with E_1/2 taken to be 0.46 V vs. SCE in CH₂Cl₂).

^gMeasured at 100 mV s⁻¹.