title: Tunable double photochromism of a family of bis-DTE bipyridine ligands and their dipolar Zn complexes.
abstract: The photoinduced ring-closure/ring-opening reactions of a series of bis-dithienylethene derivatives, as free ligands and Zn(II)-complexes, are investigated by resorting to theoretical (time-dependent density functional theory) and kinetic analyses in solution. The originality of the system stems from the tunability of the photoreaction quantum yields and conversion yields as a function of the electronic structure. The latter could be varied by modifying the electron-donating character of the DTE-end substituents L(a-d) (o,o) (a, D = H; b, D = OMe; c, D = NMe(2); d, D = NBu(2)) and/or the Lewis character of the metal ion center L(a-d)ZnX(2) (o,o) (L(a-c), X = OAc; L(d), X = Cl). The orbital description of the doubly-open form (o,o) and half-closed form (o,c) predicts that double closure to the form (c,c) would occur using UV irradiation. Photokinetic studies on the complete series demonstrate that photocyclization proceeds following a sequential ring closure mechanism. They clearly point out distinct quantum yields for the first and second ring closures, the latter being characterized by a significantly lower value. Dramatic decrease in both the quantum yields of the ring-closure and ring-opening processes is demonstrated for the complex L(d)ZnCl(2) exhibiting the strongest charge-transfer character in the series investigated. These studies show that this series of DTE derivatives provides an efficient strategy to tune the photochromic properties through the combination of the electron-donor and electron-acceptor (D-A) groups.
authors.affiliation: UMR 6226 CNRS-Université de Rennes 1, Sciences Chimiques de Rennes, Campus de Beaulieu, 35042 Rennes, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Ordronneau
authors.forename: Vincent
authors.initials: V
authors.lastname: Aubert
authors.forename: Rémi
authors.initials: R
authors.lastname: Métivier
authors.forename: Eléna
authors.initials: E
authors.lastname: Ishow
authors.forename: Julien
authors.initials: J
authors.lastname: Boixel
authors.forename: Keitaro
authors.initials: K
authors.lastname: Nakatani
authors.forename: Fatima
authors.initials: F
authors.lastname: Ibersiene
authors.forename: Dalila
authors.initials: D
authors.lastname: Hammoutène
authors.forename: Abdou
authors.initials: A
authors.lastname: Boucekkine
authors.forename: Hubert
authors.initials: H
authors.lastname: Le Bozec
authors.forename: Véronique
authors.initials: V
authors.lastname: Guerchais