title: Tuning the Direction of Intramolecular Charge Transfer and the Nature of the Fluorescent State in a T-Shaped Molecular Dyad.
abstract: Controlling photoinduced intramolecular charge transfer at the molecular scale is key to the development of molecular devices for nanooptoelectronics. Here, we describe the design, synthesis, electronic characterization, and photophysical properties of two electron donor-acceptor molecular systems that consist of tolane and BF2-containing curcuminoid chromophoric subunits connected in a T-shaped arrangement. The two π-conjugated segments intersect at the electron acceptor dioxaborine core. From steady-state electronic absorption and fluorescence emission, we find that the photophysics of the dialkylamino-substituted analogue is governed by the occurrence of two closely lying excited states. From DFT calculations, we show that excitation in either of these two states results in a distinct shift of the electron density, whether it occurs along the curcuminoid or tolane moiety. Femtosecond transient absorption spectroscopy confirmed these findings. As a consequence, the nature of the emitting state and the photophysical properties are strongly dependent on solvent polarity. Moreover, these characteristics can also be switched by protonation or complexation at the nitrogen atom of the amino group. These features set new approaches toward the construction of a three-terminal molecular system in which the lateral branch would transduce a change of electronic state and ultimately control charge transport in a molecular-scale device.
authors.affiliation: †Aix Marseille Université, CNRS, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille, France.
authors.forename: Abdellah
authors.initials: A
authors.lastname: Felouat
authors.affiliation: †Aix Marseille Université, CNRS, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille, France.
authors.forename: Anthony
authors.initials: A
authors.lastname: D'Aléo
authors.affiliation: †Aix Marseille Université, CNRS, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille, France.|‡Laboratoire CEISAM, UMR CNRS 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.
authors.forename: Azzam
authors.initials: A
authors.lastname: Charaf-Eddin
authors.affiliation: ‡Laboratoire CEISAM, UMR CNRS 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.|§Institut Universitaire de France, 103 Boulevard Saint-Michel, 75005 Paris Cedex 05, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: ∥Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes 1, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France.
authors.forename: Boris
authors.initials: B
authors.lastname: Le Guennic
authors.affiliation: ⊥Department of Physics, CNRS-Ewha International Research Center, Ewha Womans University, Seoul, South Korea.
authors.forename: Eunsun
authors.initials: E
authors.lastname: Kim
authors.affiliation: ⊥Department of Physics, CNRS-Ewha International Research Center, Ewha Womans University, Seoul, South Korea.
authors.forename: Kwang Jin
authors.initials: KJ
authors.lastname: Lee
authors.affiliation: ⊥Department of Physics, CNRS-Ewha International Research Center, Ewha Womans University, Seoul, South Korea.
authors.forename: Jae Heun
authors.initials: JH
authors.lastname: Woo
authors.affiliation: ⊥Department of Physics, CNRS-Ewha International Research Center, Ewha Womans University, Seoul, South Korea.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Ribierre
authors.affiliation: ⊥Department of Physics, CNRS-Ewha International Research Center, Ewha Womans University, Seoul, South Korea.
authors.forename: Jeong Weon
authors.initials: JW
authors.lastname: Wu
authors.affiliation: †Aix Marseille Université, CNRS, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Fages