Using a combination of ultrafast spectroscopy techniques we investigate the molecular mechanism and dynamics of different classes of emerging photoswitches.  

Donor-acceptor Stenhouse adducts (DASAs) are an emerging class of photoswitches, with advantageous properties, such as  a modular structure and rapid synthesis. They undergo large structural changes upon excitation by visible light, interconverting from an open colored form (A) to a closed colourless form (B). We have studied in detail the mechanism of DASAs photoswitching reaction, using ultrafast spectroscopy in the visible and IR regions, revealing the structure and the dynamics of formation of the reaction intermediates. 

More information can be found in:

• Zulfikri H. et al, JACS, 2019, 141, 7376-7384, DOI:10.1021/jacs.9b00341

• Lerch, M.M. et al, Angewante Chemie Int Ed, 2018, 57, 8063-8068, DOI: 10.1002/anie.201803058

• Di Donato M. et al, JACS, 2017, 139, 15596-15599, DOI: 10.1021/jacs.7b09081

Iminothioindoxyls (ITIs) are another class of photoswitches fully operated by visible light. They show a band separation of over 100 nm, isomerize on the picosecond timescale and thermally relax on the millisecond timescale. We investigated the ultrafast light induced photoisomerization of ITIs using transient absorption spectroscopy. The thermal relaxation step of ITIs is also very fast, occurring on the millisecond timescale. We furthermore discovered that protonation of the imine nitrogen can slow down thermal relaxation by several orders of magnitude. 

Learn more about ITIs on:

• Hoorens M.W.H et al, Nature Communications, 2019, 10, 2390, DOI: 10.1038/s41467-019-10251-8

• Medved' M. et al, Chemical Science, 2021, 12, 4588-4598, DOI: 10.1039/d0sc07000a