Ultrafast Excited States Dynamics of Orthogonal Photoswitches and The Influence of the Environment

Abstract Molecular photoswitches are widely used in material sciences, physics, chemistry, and biology. As needs grow more complex, materials have to react more than one‐dimensionally. The use of multiple photoswitches at once opens manifold opportunities for further improved and more complicated systems. However, this requires independent addressability, i.e., orthogonality, and reversible processes. Herein, the first study on ultrafast excited state dynamics of two orthogonal photoswitches, a push‐pull azobenzene and a donor‐acceptor Stenhouse adduct is reported. In order to gain detailed insight in their interactions and mutual influences on their photoswitching behavior, they are addressed individually and simultaneously via transient absorption spectroscopy supported by quantum chemical calculations. They show reversible photoswitchability and in addition, can be used in 4D printing to provide easy access to a plethora of functional devices. Furthermore, environmental influences on the excited state dynamics are examined using different solvents and thin films. Both compounds photoisomerize independently when addressed individually or simultaneously and only little impacts on the excited state dynamics are found. Especially the vibrational relaxation is affected by different surroundings changing the energy dissipation while hardly affecting the electronic states involved. The orthogonal and simultaneous addressability is thereby crucial for their usage in 4D printed microactuators.