J. Phys. Chem. A, 105 (12), 2911 -2924, 2001. 10.1021/jp003879d S1089-5639(00)03879-2
Web Release Date: March 22, 2001

Copyright © 2001 American Chemical Society

Absorption and Fluorescence Excitation Spectra of 9-(N-carbazolyl)-anthracene: Effects of Intramolecular Vibrational Redistribution and Diabatic Transitions Involving Electron Transfer

F. Evers, J. Giraud-Girard, S. Grimme, J. Manz,* C. Monte,# M. Oppel, W. Rettig,# P. Saalfrank, and P. Zimmermann

Institut für Atomare und Analytische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany, Laboratoire de Chimie Quantique, CNRS URA 505, IRSAMC, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France, Organisch-Chemisches Institut der Westfälischen Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany, Institut für Chemie-Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany, Institut für Chemie der Humboldt Universität Berlin, Physikalische und Theoretische Chemie, Bunsenstrasse 1, 10117 Berlin, Germany, and Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany

Received: October 20, 2000

Abstract:

The absorption and fluorescence excitation spectra of 9-(N-carbazolyl)-anthracene (C9A) in vibronically excited S1 states are measured and calculated by means of a simple model. Accordingly, C9A is excited from torsional states 0j> of the electronic ground-state S0 to diabatic torsional states 1l> of the bright electronically excited state S1, which are coupled to states 2l> of the dark electronically excited-state S2. In addition, all torsional states are coupled to the other vibrations of C9A. The model parameters are adapted from our previous papers yielding good agreement of the experimental and theoretical fluorescence emission spectrum and fluorescence lifetimes of C9A. The present additional agreement for the experimental and theoretical absorption and fluorescence excitation spectra confirms the simple model, which implies rather weak couplings of the torsional bright state S1 but strong coupling of the dark state S2 to the other vibrations of C9A, respectively. This points to different electronic structures of these excited states. This conjecture is confirmed by quantum chemical calculations based on density functional theory (DFT) that reveal the covalent structure of S1, in contrast with the TICT (twisted intramolecular charge transfer) behavior of S2.