Behavior of a chemisorbed azobenzene derivative in an STM environment: A DFT study of charged states and electric fields

► Effects of the substrate on the trans-cis isomerization of a chemisorbed azobenzene derivative are examined. ► Anionic and cationic resonance mechanisms are investigated. ► Charging reduces significantly the activation energy of the isomerization process in gas phase. ► The metallic substrate reduces the effect of charging, by delocalizing some of the charge into the surface.