title: Substituent Correlations Characterized by Hammett Constants in the Spiropyran-Merocyanine Transition.
abstract: The modification of molecular properties by the use of substituents is a versatile route for molecular design. Here we show for the example of multiresponsive spiropyrans that substituent effects and their correlations can be accurately described by Hammett constants, which in turn can be obtained directly from density functional theory calculations. The internal energetic difference ΔU between the noncolored and the colored form is determined for 63 spiropyran derivatives with substituents at the spiropyran N- and C6-positions, and can be described by only five parameters with an accuracy better than 0.1 eV (9.75 kJ/mol) using Hammett constants. This enables the prediction of ΔU values for other substituents without the need for further calculations nor experiments.
authors.affiliation: Freiburger Institut für Interaktive Materialien und Bioinspirierte Technologien , Georges-Köhler-Allee 105, 79110 Freiburg, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Brügner
authors.affiliation: Fraunhofer Institut für Werkstoffmechanik (IWM) , Wöhlerstraße 11, 79108 Freiburg, Germany.|Freiburger Materialforschungszentrum , Stefan-Meier-Straße 21, 79104 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Reichenbach
authors.affiliation: Makromolekulare Chemie, University of Freiburg , Stefan-Meier-Straße 31, 79104 Freiburg, Germany.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-2377-5998
authors.initials: M
authors.lastname: Sommer
authors.affiliation: Freiburger Institut für Interaktive Materialien und Bioinspirierte Technologien , Georges-Köhler-Allee 105, 79110 Freiburg, Germany.|Fraunhofer Institut für Werkstoffmechanik (IWM) , Wöhlerstraße 11, 79108 Freiburg, Germany.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0001-6679-2491
authors.initials: M
authors.lastname: Walter