Photoisomerization Dynamics of 2-[(<italic>E</italic>)-(4-fluorophenyl)diazenyl]-1<italic>H</italic>-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-[(<italic>E</italic>)-(4-fluorophenyl)diazenyl]-1<italic>H</italic>-imidazole (<italic>E</italic>-2g) are presented as an optical limiter through a comprehensive blend of experimental and theoretical approaches. Notably, <italic>E</italic>-2g exhibited a lower energy barrier than reported azobenzenes. The <italic>trans</italic>-to-<italic>cis</italic> photostationary state was reached in 75 min, while the <italic>cis</italic>-to-<italic>trans</italic> 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 <italic>E</italic>-2g exhibits significant nonlinear absorption characteristics, which helps in applications requiring protection from intense light sources. [ABSTRACT FROM AUTHOR]