Figure 4.

Low temperature UV/vis absorption spectra of E-NSP and of E-NMC generated at −30 °C by irradiation at 365 nm (gray solid line, initial concentration of NSP 52 μM). Addition of 1.5 equiv of CF₃SO₃H leads to formation of E-NMCH⁺ (blue solid line) with reversion to a PSS upon irradiation by the light source of the UV/vis spectrometer (red solid line).