Ultrafast Hemithioindigo-based peptide-switches

Four newly synthesized Hemithioindigo-based peptide-switches with changing meta/para-substitution-pattern within the stilbene-part of the molecule are characterized with time-resolved absorption spectroscopy. The different substances undergo a light-induced Z/E-isomerization: the reaction proceeds on a picosecond timescale with time constants <50 ps for the Z → E photoreaction and <10 ps for the inverse process from E → Z. The reaction times strongly depend on the specific substitution-pattern: fast reaction dynamics (<10 ps) are observed for the direct attachment of electron donating groups in the para-position. The molecular mechanism of the isomerization-process can be described with the same reaction model as used for related systems. The presented Hemithioindigos are hence promising alternatives to Azobenzene-switches due to their fast switching speed, improved spectral characteristics and an improved stability.