Abstract
Bicyclic aziridine (1,3-diazabicyclo[3.1.0]-hex-3-enes) has derivatives (DABH) known for their photochromic properties. A photochromic compound undergoes reversible isomerization between two states upon light irradiation. In the transition from the closed-ring to open-ring form, formal charges are generated in the more conjugated open-ring state. Thiophene and thiazole, known for their electron-rich nature and high charge mobility, were conjugated to a DABH substituent. We report the synthesis of DABH conjugated to thiophene (Th-DABH) and thiazole (Tz- DABH), both of which exhibit photochromic behaviors in the solution and the solid state. Optical absorbance measurements revealed a redshift in the maximum absorption wavelength λ(max) from 437 to 440 nm in solution to 618 to 632 nm in the solid state. Notably, the photogenerated state demonstrated significantly extended lifetimes in the solid state, over 2 and 3 orders of magnitude longer than in the methanol solution (Th-DABH 176 times, Tz-DABH 2750 times). Both compounds exhibited reversible switching over multiple cycles in the solid state. Structural analysis via single-crystal X-ray diffraction and ab initio calculations provided insights into the observed photochromic behavior. These findings suggest that integrating DABH-based photochromic materials into optoelectronic devices or organic field-effect transistors could enable stimuli-responsive materials whose electronic properties can be modulated by an external light source.