Fig. 5. FTIR spectra of E-P1 and Z-P1 in DCM (100 mg mL⁻¹) focused on (a) N–H and (b) C O stretching vibrations. (c) ¹H NMR spectra (500 MHz) of E-P1 and Z-P1 in CD₂Cl₂. (d) Illustration of intrachain and interchain hydrogen bonding in Z-P1 and E-P1, respectively. (e) Pictures of photoreversible precipitation and dissolution of Z-P1 in toluene (0.90 mM) by 405 nm irradiation for 7 min and subsequent 300 nm irradiation for 9.5 min. Transmittance changes of toluene solutions of Z-P1 at 0.10, 0.30, and 0.90 mM during (f) 405 nm irradiation and (g) subsequent 300 nm irradiation. (h) Transmittance changes of toluene solutions of Z-P1 at 0.30 and 0.90 mM upon alternating irradiation with 405 and 300 nm light.