Molecular lambda shape light-driven dual switches: Spectroscopic and computational studies of the photoisomerization of bisazo Tröger base analogs

Bisazo Tröger base analogs are claw-looking molecules that carry two identical but independent photoswitching groups. These bisazo compounds, like dual switches, can be at EE, EZ, and ZZ photoisomerization states while the ∧-shape void of Tröger base scaffold may also introduce an additional possibility of stereoisomerism by holding the photoisomerizable groups in endo or exo positions. To date, the exact molecular geometries of the isomerizable analogs of Tröger's base have not been elaborated. Owing to the special features and potential applications of these molecules, herein their photoisomerization is probed. The gleaned data from ¹⁵N isotope labeling and a variety of spectroscopic, spectrophotometric, crystallographic, and computational techniques have revealed the structure of the studied photoisomers and suggested their use in the design of molecular pull and push mechanisms, light driven actuators, and artificial muscles.