Fig. 1.

UV-Vis spectra of N-methyl-4,4′-bipyridinium (MQ⁺) + p-methylphenol (p-MePhOH) where each spectrum was obtained with equimolar MQ⁺ and p-MePhOH in the concentration range of 5–50 mM, in 50 mM Tris buffer, pH 8.5, ionic strength maintained at I = 0.8 M with NaCl at 23 ± 2 °C. Inset shows plot of absorbance at 360 nm as a function of the extent of adduct formation. The titration data are summarized in Table S1.