Table 1. Summary of the pK_a Values of Three Hairpin-Shaped Polyamides (PIP-3, PIP-4, and PIP-1) and Cyclic Polyamide PIP-5.

^aConcentrations of polyamides were calculated using a molar absorptivity ε = 69500 M^–1 cm^–1 at 310 nm by UV–vis spectroscopy. All of the compounds were prepared in neat DMSO and then diluted with water to a final concentration of 0.1% DMSO.

^bErrors represent standard deviations of three independent measurements.