title: Excited-state properties and emission spectra of nonplanar heterocyclic helicenes.
abstract: We discuss the electron-vibration coupling in mono-aza-[5]helicenes on the basis of a Franck-Condon analysis and density functional theory (DFT) calculations of the fluorescence and phosphorescence spectra measured in ethanol. The geometries of the initial states were obtained from time-dependent DFT (S(1)) and unrestricted DFT (T(1)) excited-state optimizations. In general, the position of the nitrogen atom has only a minor impact on the vibronic fine-structure in both absorption and emission. The shapes of the emission spectra from the lowest singlet and triplet states are found to be determined by contributions from multiple normal modes. The results of the calculations demonstrate how the interplay among these normal modes results in qualitatively and quantitatively different spectra for fluorescence and phosphorescence.
authors.affiliation: School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30322-440, USA.
authors.forename: Karin
authors.initials: K
authors.lastname: Schmidt
authors.forename: Sergio
authors.initials: S
authors.lastname: Brovelli
authors.forename: Veaceslav
authors.initials: V
authors.lastname: Coropceanu
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas
authors.forename: Cristina
authors.initials: C
authors.lastname: Bazzini
authors.forename: Tullio
authors.initials: T
authors.lastname: Caronna
authors.forename: Riccardo
authors.initials: R
authors.lastname: Tubino
authors.forename: Francesco
authors.initials: F
authors.lastname: Meinardi