title: Novel photoswitchable receptors: synthesis and cation-induced self-assembly into dimeric complexes leading to stereospecific [2+2]-photocycloaddition of styryl dyes containing a 15-crown-5 ether unit.
abstract: Styryl dyes 4a-e containing a 15-crown-5 ether unit and a quinoline residue with a sulfonatoalkyl or sulfonatobenzyl N-substituent were synthesized. The relationship between the photochemical behavior of these dyes and their aggregates derived from complexation with Mg(2+) in MeCN was studied using (1)H NMR and absorption spectroscopy. The E-isomers of 4a-e were shown to form highly stable dimeric (2:2) complexes with Mg(2+). Upon irradiation with visible light, the dimeric complexes undergo two competing photoreactions, viz., geometric E --> Z isomerization, resulting in an anion-capped 1:1 complex of the Z-isomer with Mg(2+) and stereospecific syn-head-to-tail [2+2]-cycloaddition, affording a single isomer of bis-crown-containing cyclobutane. The N-substituent in the dye has a dramatic effect on the photochemical behavior of the dimeric complex. Molecular dynamics and semiempirical quantum-chemical calculations were carried out to interpret the observed photocycloaddition in the dimer. Conformational equilibria for the dimer of (E)-4b were analyzed using (1)H NMR spectroscopy.
authors.affiliation: Photochemistry Center of the Russian Academy of Sciences, 7a ul Novatorov, Moscow 119421, Russia.
authors.forename: Sergey P
authors.initials: SP
authors.lastname: Gromov
authors.forename: Evgeny N
authors.initials: EN
authors.lastname: Ushakov
authors.forename: Olga A
authors.initials: OA
authors.lastname: Fedorova
authors.forename: Igor I
authors.initials: II
authors.lastname: Baskin
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Buevich
authors.forename: Elena N
authors.initials: EN
authors.lastname: Andryukhina
authors.forename: Michael V
authors.initials: MV
authors.lastname: Alfimov
authors.forename: Dan
authors.initials: D
authors.lastname: Johnels
authors.forename: Ulf G
authors.initials: UG
authors.lastname: Edlund
authors.forename: James K
authors.initials: JK
authors.lastname: Whitesell
authors.forename: Marye Anne
authors.initials: MA
authors.lastname: Fox