Sunlight-triggered photochromism of imidazole-based 2D polymer via open–shell diradicalization

The imidazole-incorporated CMP exhibits rapid sunlight-activated photochromic behaviour, altering its solid-state colour from yellow (red edge at 834 nm) to green (red edge at 1240 nm) with reversion in darkness. The process is attributed to a unique open-shell diradicalization of the CMP, as evidenced by EPR, SQUID, NMR, and FT-IR analyses.