Concentrations of monomeric (Cm) and aggregate (Ct-Cm) forms of 11, 12, and 5 were calculated from absorbance spectra and replotted on double logarithmic scales. Each point represents a spectrum collected at a different bulk compound concentration, whereas each line represents best fit of the data points to a linear regression. Regression slopes for 11, 12, and 5 were 2.3 ± 0.1, 1.8 ± 0.1, and 1.7 ± 0.1, respectively, consistent with dimerization being mostly responsible for the spectral shifts of all three compounds.