Effect of substitution position of aryl groups on the thermal back reactivity of aza-diarylethene photoswitches and prediction by density functional theory.

Aza-diarylethene has been developed as a new family of photochromic compounds. This study explores the photochromic properties and thermal back reactivities of various aza-diarylethene regioisomers (N1-N4 and I1-I4) in n-hexane. These molecules exhibit fast thermally reversible photochromic reactions driven by 6π aza-electrocyclization. Kinetic analysis of the thermal back reaction revealed activation parameters, highlighting how the substitution position of the aryl group affects the thermal stability. Additionally, density functional theory calculations identified M06 and MPW1PW91 as the most accurate functionals for predicting the thermal back reactivity, closely matching the experimental data. These findings offer valuable insights for the design of advanced photochromic materials with tailored thermal and photophysical characteristics.