Ten new 1,3-diazabicyclo-[3.1.0]hex-3-ene-based azo dyes (3a–3k) were synthesized via three-component
reaction between [3-(x-phenyl)aziridin-2-yl](phenyl)methanone (x = 4-NO2, 3-NO2), NH4OAc and azocoupled
o-vanillin or salicylaldehyde precursors (1a–1e) and characterized by UV–Vis, IR and 1H NMR spectroscopic
techniques. The synthesized azo dyes undergo ring opening in EtOH by irradiation with 254 nm UV
light. The properties and photochromic structural behavior relationship (PSBR) of these dyes has been analyzed.
The spectroscopic information show that the close-E photoisomer prevails in ordinary room light,
however by irradiation with UV light the open-Z photoisomer is prominent.
