Hydrogen‐bonding donor‐acceptor Stenhouse adducts

The binding of donor-acceptor Stenhouse adducts (DASAs) bearing hydrogen-bond recognition groups by Hamilton-type receptors significantly influenced their photoswitching properties by altering thermal barriers to isomerization. The thermal barrier between the most stable linear isomer and the photogenerated isomer is lowered on binding to a receptor, and this barrier is crucial for switching properties. The thermal isomerization was shown to proceed via a stepwise linear-enol-keto mechanism in DMSO where the tautomerisation barrier is within 2 kJ ⋅ mol of that of the rate-determining step, which may be important for analyzing switching properties.