title: Photophysical Properties of Benzoylgermane and para-Substituted Derivatives: Substituent Effects on Electronic Transitions.
abstract: In the present study, a selection of basic substitution patterns on benzoyl(trimethyl)germane was investigated using time-dependent density-functional theory (TDDFT) to explore the influence on the stability and on the relative order of the lowest excited electronic states. The theoretical results are in agreement with absorption and fluorescence measurements. We show that electron-withdrawing groups decrease the energetic level of the lowest singlet and triplet state relative to the electron-pushing systems resulting in red-shifted radiative transitions (fluorescence). In the first triplet state electron-withdrawing groups lead to an increased dissociation barrier and a close approach with the singlet ground state before the transition state in the triplet state is reached, favoring radiationless ground-state recovery. The results are also in good agreement with empirical concepts of organic chemistry, therefore providing simple rules for synthetic strategies towards tuning the excited-state properties of benzoylgermanes.
authors.affiliation: Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, 76049, Karlsruhe, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Feuerstein
authors.affiliation: Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, 76049, Karlsruhe, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Höfener
authors.affiliation: Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, 76049, Karlsruhe, Germany.
authors.forename: Wim
authors.initials: W
authors.lastname: Klopper
authors.affiliation: Ivoclar Vivadent AG, Bendererstr. 2, 9494, Schaan, Liechtenstein.
authors.forename: Iris
authors.initials: I
authors.lastname: Lamparth
authors.affiliation: Ivoclar Vivadent AG, Bendererstr. 2, 9494, Schaan, Liechtenstein.
authors.forename: Norbert
authors.initials: N
authors.lastname: Moszner
authors.affiliation: Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76128, Karlsruhe, Germany.|Institut für Biologische Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Barner-Kowollik
authors.affiliation: Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, 76049, Karlsruhe, Germany.
authors.forename: Andreas-N
authors.initials: AN
authors.lastname: Unterreiner
keywords: benzoylgermanes; density functional calculations; excited states; fluorescence; transition states