title: Modulation of the La/LbMixing in an Indole Derivative: A Position-Dependent Study Using 4-, 5-, and 6-Fluoroindole.
abstract: The lowest two electronically excited singlet states of indole and its derivatives are labeled as Laor Lb, based on the orientation of the transition dipole moment (TDM) and the magnitude of the permanent electric dipole moment. Rotationally resolved electronic Stark spectroscopy in combination with high level ab initio calculations offers the possibility to determine these characteristics and thus the electronic nature of the excited states. In the present contribution this approach was pursued for the systems 4- and 6-fluoroindole and the results compared to the previously investigated system 5-fluoroindole. Changing the position of the fluorine atom from 5 to 4 or 6 is accompanied by an increasing amount of Lacharacter in the S1state. This dramatically influences the orientation of the TDM and erases its ability to be a reasonable identifier of the nature of the excited states for both molecules. However, for 4-fluoroindole, where the influence of the Lais weak, the nature of the S1state can still be assigned to be mainly Lbbased on the excited state dipole moment. For 6-fluoroindole, this is not the case anymore, and the La/Lbnomenclature completely breaks down due to heavily mixed excited states.
authors.affiliation: Institut für Physikalische Chemie I, Heinrich-Heine-Universität , D-40225 Düsseldorf, Germany.
authors.forename: Josefin
authors.initials: J
authors.lastname: Wilke
authors.affiliation: Institut für Physikalische Chemie I, Heinrich-Heine-Universität , D-40225 Düsseldorf, Germany.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0002-9430-1909
authors.initials: M
authors.lastname: Wilke
authors.affiliation: Institut für Physikalische Chemie I, Heinrich-Heine-Universität , D-40225 Düsseldorf, Germany.|Faculty of Physics, VCQ, University of Vienna , Boltzmanngasse 5, A-1090 Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Brand
authors.affiliation: Institut für Theoretische Chemie und Computerchemie, Heinrich-Heine-Universität , D-40225 Düsseldorf, Germany.
authors.forename: J Dominik
authors.initials: JD
authors.lastname: Spiegel
authors.affiliation: Institut für Theoretische Chemie und Computerchemie, Heinrich-Heine-Universität , D-40225 Düsseldorf, Germany.
authors.forename: Christel M
authors.identifier: http://orcid.org/0000-0001-7148-0900
authors.initials: CM
authors.lastname: Marian
authors.affiliation: Institut für Physikalische Chemie I, Heinrich-Heine-Universität , D-40225 Düsseldorf, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schmitt