All-photonic switching of a benzo[<i>e</i>]-fused dimethyldihydropyrene–azobenzene dyad in the solid-state for logic operations

Molecular photoswitches are crucial components for developing high-density memory devices and photonic information processing systems. A molecular photoswitch can generate at least two distinct states. Photochromic dyads of coupled photoswitches can attain more than two states if the two switches are independently addressable. However, orthogonal photoswitching in hybrid photochromic systems could be challenging. In this work, we discuss the development of two orthogonal hybrid photochromic dyads integrating two distinct photoswitches: dimethyldihydropyrene (DHP) or benzo[<i>e</i>]-fused dimethyldihydropyrene (BDHP) with azobenzene. Despite the significant spectral overlap between these systems, careful design and selection of suitable light sources ranging from NIR to UV light have successfully decoupled the individual photoswitching processes. As a result, four distinct well-characterized states can be selectively controlled with light. We constructed an all-photonic molecular logic gate by switching the system in a thin film, showcasing the potential of these systems for advanced molecular information processing using attenuated total reflectance (ATR)-based FTIR spectroscopy as a non-destructive readout mode.