Shedding Light on the Photoisomerization Pathway of Donor–Acceptor Stenhouse Adducts

摘要: Donor–acceptor Stenhouse adducts (DASAs) are negative photochromes that hold great promise for a variety of applications. Key to optimizing their switching properties is detailed understanding the photoswitching mechanism, which, as yet, absent. Here we characterize actinic step DASA-photoswitching and its key intermediate, which was studied using combination ultrafast visible IR pump–probe spectroscopies TD-DFT calculations. Comparison time-resolved spectra with DFT computations allowed unambiguously identify structure confirming light absorption induces sequential reaction path in Z–E photoisomerization C2–C3 followed by rotation around C3–C4 subsequent thermal cyclization step. First second-generation DASAs share common mechanism chlorinated solvents notable differences kinetics lifetimes excited states. The photogenerated intermediate DA...