Details

Autor(en) / Beteiligte

• Ushakov, Evgeny N.
• Martyanov, Timofey P.
• Vedernikov, Artem I.
• Pikalov, Oleg V.
• Efremova, Asya A.
• Kuz’mina, Lyudmila G.
• Howard, Judith A.K.
• Alfimov, Michael V.
• Gromov, Sergey P.

Titel

Self-assembly through hydrogen bonding and photochemical properties of supramolecular complexes of bis(18-crown-6)stilbene with alkanediammonium ions

Ist Teil von

• Journal of photochemistry and photobiology. A, Chemistry., 2017-05, Vol.340, p.80-87

Ort / Verlag

Lausanne: Elsevier B.V

Erscheinungsjahr

2017

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• [Display omitted] •Supramolecular 2:2 complexes of (E)-bis(18-crown-6)stilbene with +H3N(CH2)nNH3+.•The quantum yields of competing photoreactions in the 2:2 complexes are measured.•Pseudocyclic 1:1 complexes of (Z)-bis(18-crown-6)stilbene with +H3N(CH2)nNH3+.•The peculiar spectral properties of the Z isomer complexes are interpreted.•Co-crystallization of the E isomer with +H3N(CH2)6NH3+2ClO4− affords a polymer. Binding of alkanediammonium ions +H3N(CH2)nNH3+, n=2–6, to (E)-bis(18-crown-6)stilbene initiates the [2+2] photocycloaddition reaction leading mainly to the rctt isomer of 1,2,3,4-tetrakis(benzo-18-crown-6)cyclobutane. The high efficiency and stereoselectivity of this photoreaction in dilute solution are due to the formation of bis-pseudosandwich complexes consisting of two stilbene molecules and two alkanediammonium ions. With a decrease in the length of the polymethylene spacers in the 2:2 complex, the quantum yield of supramolecular [2+2] photocycloaddition increases from 0.02 to 0.27, while the quantum yield of the competing E–Z photoisomerization decreases from 0.12 to 0.06. Spectrophotometric observations and density functional theory calculations revealed that (Z)-bis(18-crown-6)stilbene, unlike the E isomer, is able to form pseudocyclic 1:1 complexes with +H3N(CH2)nNH3+, n=2–6, owing to the proximity of two crown ether moieties. The peculiar spectral properties of these complexes are associated with large torsion angles around the ethylene–benzocrown single bonds. X-ray diffraction analysis showed that co-crystallization of (E)-bis(18-crown-6)stilbene with 1,6-hexanediammonium diperchlorate affords a linear polymer in which the alternating stilbene molecules and diammonium ions are connected by hydrogen bonds.