Photoisomerization Dynamics of 2-[(E)-(4-fluorophenyl)diazenyl]- 1H-imidazole: A Theoretical and Experimental Insight

This study investigates the photoresponsive behavior of substituted azobenzenes with a specific focus on their nonlinear optical response. This study suggests that azoimidazole substitution is a better alternative to azobenzene derivatives for nonlinear optical responses. The synthesis, characterization, photophysical property and isomerization pathway of 2-[([Formula: see text]-(4-fluorophenyl)diazenyl]-1[Formula: see text]-imidazole ([Formula: see text]-2g) are presented as an optical limiter through a comprehensive blend of experimental and theoretical approaches. Notably, [Formula: see text]-2g exhibited a lower energy barrier than reported azobenzenes. The trans-to-cis photostationary state was reached in 75 min, while the cis-to-trans state was achieved in 60 min at 354 nm. The study further explores the photoisomerization pathway of E-2g, highlighting its nonlinear absorption, which has a nonlinear absorption coefficient ([Formula: see text]eff) of 8.8 × 10[Formula: see text] m/W at 20 [Formula: see text]J, as determined by [Formula: see text]-scan measurements. The results suggest that [Formula: see text]-2g exhibits significant nonlinear absorption characteristics, which helps in applications requiring protection from intense light sources.