Fluorination effects on photoisomerization dynamics of azobenzene

Abstract

The photoisomerization dynamics of azobenzene (Azo-H) and its modulation by electron-withdrawing groups (EWGs) are important for designing photophysical applications, such as artificial muscles, liquid crystal displays, and solar thermal fuels. In this study, the electron-withdrawal kinetics of fluorination and the tailoring of the photoisomerization dynamics of azobenzene were explored using theoretical multiscale simulations. First-principle calculations provide insight into the mechanical aspects of photoisomerization, whereas molecular dynamics simulations offer a time-dependent perspective. Fluorinated azobenzene (Azo-F) exhibits superior photoisomerization responsiveness owing to changes in its molecular conformation and energy states induced by the EWG. These thermodynamic advantages were influenced by the stabilization of the molecular orbitals near the diazene groups. Despite the thermodynamic advantages of Azo-F, heavy fluorine atoms reduce the actuating force and work capacity owing to their increased inertia. This study provides a comprehensive understanding of photoisomerization kinetics modulated by the local fluorination of Azo-H. © 2024 Elsevier B.V.