Regular Arrays of Rod‐Shaped Molecular Photoswitches: Synthesis, Preparation, Characterization, and Selective Photoswitching within Mono‐ and Bilayer Systems

Abstract

We assembled photoresponsive mono‐ and bilayer systems with well‐defined properties from rod‐shaped molecules equipped with different photoswitches. Using properly chosen chromophores (diarylethene‐based switch and unidirectional light‐driven molecular motor), we then selectively targeted layers made of the same types of photoswitches using appropriate monochromatic light. UV–vis analysis confirmed smooth and unrestricted photoisomerization. To achieve this, we synthesized a new class of triptycene‐based molecular pedestals adept at forming sturdy Langmuir–Blodgett films on a water–air interface. The films were smoothly transferred to gold and quartz surfaces. Repeated deposition afforded bilayer systems: one layer containing diarylethene‐based photoswitches and the other a unidirectional light‐driven molecular motor. Structural analysis of both mono‐ and bilayer systems revealed the molecules to be tilted with carboxylic functions pointing to the surface. At least two different polymorphs differing in monolayer thickness and tilt angle (⁓40° and ⁓60°) were identified on the gold surface.