title: Ingredients to TICT Formation in Donor Substituted Hemithioindigo.
abstract: Twisted intramolecular charge transfer (TICT) formation in hemithioindigo photoswitches has recently been reported and constitutes a second deexcitation pathway complementary to photoisomerization. Typically, this behavior is not found for this type of photoswitches, and it takes special geometric and electronic conditions to realize it. Here we present a systematic study that identifies the molecular preconditions leading to TICT formation in donor substituted hemithioindigo, which can thus serve as a frame of reference for other photoswitching systems. By varying the substitution pattern and providing an in-depth physical characterization including time-resolved and quantum yield measurements, we found that neither ground-state pretwisting along the rotatable single bond nor the introduction of strong push-pull character across the photoisomerizable double bond alone leads to formation of TICT states. Only the combination of both ingredients produces light-induced TICT behavior in polar solvents.
authors.affiliation: Department für Chemie and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München , D-81377 Munich, Germany.
authors.forename: Sandra
authors.identifier: http://orcid.org/0000-0002-5797-4522
authors.initials: S
authors.lastname: Wiedbrauk
authors.affiliation: Institut für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München , D-80538 Munich, Germany.
authors.forename: Benjamin
authors.identifier: http://orcid.org/0000-0001-9242-1918
authors.initials: B
authors.lastname: Maerz
authors.affiliation: Institut für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München , D-80538 Munich, Germany.
authors.forename: Elena
authors.identifier: http://orcid.org/0000-0002-8186-3638
authors.initials: E
authors.lastname: Samoylova
authors.affiliation: Department für Chemie and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München , D-81377 Munich, Germany.
authors.forename: Peter
authors.identifier: http://orcid.org/0000-0002-1847-8032
authors.initials: P
authors.lastname: Mayer
authors.affiliation: Institut für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München , D-80538 Munich, Germany.
authors.forename: Wolfgang
authors.identifier: http://orcid.org/0000-0003-3695-9486
authors.initials: W
authors.lastname: Zinth
authors.affiliation: Department für Chemie and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München , D-81377 Munich, Germany.
authors.forename: Henry
authors.identifier: http://orcid.org/0000-0002-5055-9924
authors.initials: H
authors.lastname: Dube