title: Is energy transfer limiting multiphotochromism? answers from ab initio quantifications.
abstract: Dithienylethenes (DTEs) can be assembled to form supramolecular multiphotochromic systems that are highly functional molecular architectures of potential interest for building complex optoelectronic devices. Yet even simple DTE dimers relying on an organic linker may suffer from a partial photoactivity, i.e., only one of the two switches does isomerise. Experimentally, this limited photochromism has been attributed to an excited state energy transfer (EET) between the two DTEs of the multimer; this EET taking place instead of the desired photoinduced cyclisation of the DTE. However, no clear evidences of this phenomenon have been provided so far. In this work we propose the first rationalisation of this potential parasite photoinduced event using a computational approach based on Time-Dependent Density Functional Theory (TD-DFT) for the calculation of the electronic coupling in DTE dimers. Besides quantifying EET in several systems, we dissect the role of through-bond and through-space mechanisms on this process and clarify their dependence on both the nature and length of the bridge separating the two photochromes. The theoretical data obtained in this framework are in full agreement with the experimental outcomes and pave the way toward a molecular design of coupled, yet fully functionals, DTE-based multiswitches.
authors.affiliation: Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes1, 263 Av. du Général Leclerc, 35042, Cedex Rennes, France. Arnaud.Fihey@univ-rennes1.fr and CEISAM, UMR CNRS 6230, Université de Nantes, 2, Rue de la Houssinière, BP 92208, 44322 Nantes, Cedex 3, France. Denis.Jacquemin@univ-nantes.fr.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Fihey
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Universitá di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy. benedetta.mennucci@unipi.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Russo
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Universitá di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy. benedetta.mennucci@unipi.it.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Cupellini
authors.affiliation: CEISAM, UMR CNRS 6230, Université de Nantes, 2, Rue de la Houssinière, BP 92208, 44322 Nantes, Cedex 3, France. Denis.Jacquemin@univ-nantes.fr and Institut Universitaire de France, 1 rue Descartes, 75231 Paris Cedex 5, France.
authors.forename: Denis
authors.identifier: http://orcid.org/0000-0002-4217-0708
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Universitá di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy. benedetta.mennucci@unipi.it.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mennucci