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

Abstract

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-[(E)-(4-fluorophenyl)diazenyl]-1H-imidazole (E-2g) are presented as an optical limiter through a comprehensive blend of experimental and theoretical approaches. Notably, E-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 (βeff) of 8.8 × 10−11 m/W at 20 μJ, as determined by Z-scan measurements. The results suggest that E-2g exhibits significant nonlinear absorption characteristics, which helps in applications requiring protection from intense light sources