Fig. 1: Sturctures of photochromic molecules and photoswtichable spetra of PMCs.
From: Photochromism of pyridine-substituted merocyanine through reversible C-N bond formation

A Photochromic reaction of spiropyran and diarylethene. B Reported examples of photochromism involving reversible C-N bond. C Structures of PMCs and their photoisomerization mechanism. D Absorption spectra of PMC1-5 in water before and after irradiation with white light-emitting diode (LED) for 10 s.