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URN: urn:nbn:de:kobv:517-opus-13168
URL: http://opus.kobv.de/ubp/volltexte/2007/1316/


Kaafarani, Bilal R. ; Wex, Brigitte ; Strehmel, Bernd ; Neckers, Douglas C.

Structural concept for fluorinated Y-enynes with solvatochromic properties

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Kurzfassung in Englisch

An approach to the development of fluorescent probes to follow polymerizations in situ using fluorinated cross-conjugated enediynes (Y-enynes) is reported. Different substitution patterns in the Y-enynes result in distinct solvatochromic behavior. β,β-Bis(phenylethynyl)pentafluorostyrene 7, which bears no donor substituents and only fluorine at the styrene moiety, shows no solvatochromism. Donor substituted β,β-bis(3,4,5-trimethoxyphenylethynyl)
pentafluorostyrene 8 and β,β-bis(4-butyl-2,3,5,6-tetrafluorophenylethynyl)-3,4,5-trimethoxystyrene 9
exhibit solvatochromism upon change of solvent polarity. Y-enyne 8 showed the largest solvatochromic shift (94 nm bathochromic shift) upon changing solvent from cyclohexane to acetonitrile. A smaller solvatochromic response
(44 nm bathochromic shift) was observed for 9. Lippert–Mataga treatment of 8 and 9 yields slopes of -10,800 and -6,400 cm -1, respectively. This corresponds to a change in dipole moment of 9.6 and 6.9 D, respectively. The solvatochromic behavior in 8 and 9 supports the formation of an intramolecular charge transfer (ICT) state. The low fluorescence quantum yields are caused by competitive double bond rotation. The fluorescence decay time of 9 decreases in methyltetrahydrofuran from 2.1 ns at 77 K to 0.11 ns at 200 K. Efficient single bond rotation in 9 was frozen at -50 °C in a configuration in which the trimethoxyphenyl ring is perpendicular to the fluorinated rings.
7–9 are photostable compounds. The X-ray structure of 7 shows it is not planar and that its conjugation is distorted.
Y-enyne 7 stacks in the solid state showing coulombic, actetylene–arene, and fluorine–π interactions.

Collection: Universität Potsdam / Aufsätze (Pre- und Postprints) / Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie / Physikalische Chemie
Institut 1: Institut für Chemie
Institut 2: Extern
DDC-Sachgruppe: Chemie
Dokumentart: c Postprint
Schriftenreihe: Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, ISSN 1866-8372
Bandnummer: paper 027
Quelle: Photochemical and Photobiological Sciences. - ISSN 1474-905X. - 1 (2002), p. 942-950
Sprache: Englisch
Erstellungsjahr: 2002
Publikationsdatum: 25.04.2007
Bemerkung:
first published in:
Photochemical and Photobiological Sciences : an international journal ; the official journal of the European Photochemistry Association and the European Society for Photobiology. - ISSN 1474-905X. - 1 (2002), S. 942-950
doi: 10.1039/b208326d
Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology and the European Photochemistry Association


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