title: Spatially close azo dyes with sub-nanosecond switching speeds and exceptional temporal resolution.
abstract: Photoswitchable bis-azo dyes with an outstanding temporal resolution of 10(15) times between the thermal relaxation rates of their two constituting photochromes are reported. Remarkably, the close spatial proximity of both azo photochromes in these molecular assemblies translates in an unprecedented 10(3) -fold acceleration of the thermal isomerization rate of their faster azo unit compared to the one displayed by the isolated counterpart. Indeed, the relaxation time of the fast-isomerizing platform of the herein reported bis-azobenzenes is as low as 200 ps under ambient conditions. In the wake of these results, the bis-azo dyes described herein are invaluable chromophores for the design of multifunctional light-addressable materials in which simultaneous switching in two very different timescales might be essential.
authors.affiliation: Grup de Materials Orgànics, Departament de Química Orgànica, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franqués 1, 08028- Barcelona (Spain).
authors.forename: Jaume
authors.initials: J
authors.lastname: Garcia-Amorós
authors.affiliation: Grup de Materials Orgànics, Departament de Química Orgànica, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franqués 1, 08028- Barcelona (Spain).
authors.forename: Alba
authors.initials: A
authors.lastname: Cuadrado
authors.affiliation: Grup de Materials Orgànics, Departament de Química Orgànica, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franqués 1, 08028- Barcelona (Spain).
authors.forename: Marta
authors.initials: M
authors.lastname: Reig
authors.affiliation: Laboratoire de Spectrochimie Infrarouge et Raman CNRS UMR 8516, Université de Lille 1 Sciences et Technologies, Université Lille Nord de France, Bat C5, 59655, Villeneuve d'Ascq Cedex (France).
authors.forename: Vincent
authors.initials: V
authors.lastname: De Waele
authors.affiliation: Laboratoire de Spectrochimie Infrarouge et Raman CNRS UMR 8516, Université de Lille 1 Sciences et Technologies, Université Lille Nord de France, Bat C5, 59655, Villeneuve d'Ascq Cedex (France). olivier.poizat@univ-lille1.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Poizat
authors.affiliation: Grup de Materials Orgànics, Departament de Química Orgànica, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franqués 1, 08028- Barcelona (Spain). dvelasco@ub.edu.
authors.forename: Dolores
authors.initials: D
authors.lastname: Velasco
keywords: azobenzenes; molecular switches; photoactive materials; photochemistry; ultrafast flash-photolysis