title: Metal ions drive thermodynamics and photochemistry of the bis(styryl) macrocyclic tweezer.
abstract: UV/Vis and NMR spectroscopy were used for the structural elucidation and thermodynamic and photochemical studies of the metal-coordinated crown-containing macrocyclic tweezer (E,E)-1. The bis(styryl) tweezer (E,E)-1 formed two types of complexes with magnesium(II): a 1:1 intramolecular asymmetric sandwich complex [(E,E)-1].Mg(2+) and a 1:2 complex [(E,E)-1].(Mg(2+))(2). In the former case, there is direct cation intramolecular exchange (0.299 s(-1), DeltaG(++)=69.4 kJ mol(-1)) between two parts of the bis(styryl) tweezer (E,E)-1. Addition of barium(II) to the bis(styryl) tweezer (E,E)-1 led to an intramolecular centrosymmetric sandwich 1:1 complex [(E,E)-1].Ba(2+). Irradiation of [(E,E)-1]Ba(2+) afforded reversible intramolecular [2pi+2pi] photocyclization with excellent stereoselectivity and quantitative yield. In contrast, irradiation of [(E,E)-1].(Mg(2+))(2) resulted in reversible stepwise E,Z-isomerization.
authors.affiliation: CNRS UMR 8516, Université Lille Nord de France, UDSL, 3 rue du Professeur Laguesse BP83, 59006 Lille, France.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Tulyakova
authors.forename: Gaston
authors.initials: G
authors.lastname: Vermeersch
authors.forename: Elena N
authors.initials: EN
authors.lastname: Gulakova
authors.forename: Olga A
authors.initials: OA
authors.lastname: Fedorova
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Fedorov
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Micheau
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Delbaere