Synthesis and Photochromism of Diazocine Derivatives: Relationship Between Photoswitching Properties and Molecular Structures

We design and synthesize five novel diazocine derivatives, using diazocine as the core, amide or imine bonds as the connecting units attached with different peripheral substituents. The photoisomerization yield and thermal stability of these derivatives are tested by ¹H NMR and UV-Vis absorption spectroscopy. Among them, the imine-linked derivative exhibits the lowest photoisomerization efficiency, while the amide-linked ones show an elevated switching efficiency in transitioning from the cis to the trans configuration, compared to the unmodified 3,3′-diamino-diazocine. Furthermore, based on experiments together with density functional theory (DFT) calculations, we find that the thermal stability of these derivatives is associated with the electron cloud density and steric hindrance of their substituents. Owing to these unique photophysical properties, diazocine derivatives provide a foundation for the development and application of molecular optical switches.