1,3-bicyclo[1.1.1]pentanediyl: the shortest rigid linear connector of phenylated photochromic units and a 1,5-dimethoxy-9,10-di(phenylethynyl)anthracene fluorophore |
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Authors: | de Meijere Armin Zhao Ligang Belov Vladimir N Bossi Mariano Noltemeyer Matthias Hell Stefan W |
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Affiliation: | 1. Institut für Organische und Biomolekulare Chemie, Georg‐August‐Universit?t G?ttingen, Tammannstrasse 2, 37077 G?ttingen, Germany, Fax: (+49)?551‐399‐572;2. KademCustomChem GmbH, Brombeerweg 13, 37077 G?ttingen, Germany, Fax: (+49)?551‐23423;3. Department of Nanobiophotonics, Max‐Planck‐Institute for Biophysical Chemistry, Am Fassberg 11, 37077 G?ttingen, Germany, Fax: (+49)?551‐201‐2505;4. Institut für Anorganische Chemie, Georg‐August‐Universit?t G?ttingen, Tammannstrasse 4, 37077 G?ttingen, Germany, Fax: (+49)?551‐393‐373 |
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Abstract: | An excess of bis-1,3-(4-iodophenyl)bicyclo[1.1.1]pentane, prepared in 63 % yield by iodination of 1,3-diphenylbicyclo[1.1.1]pentane, was selectively mono-coupled with 9-ethynyl-1,5-dimethoxy-10-phenylethynylanthracene (26), and subsequently with the zinc derivatives of 1-(2-methyl/methoxy-4-methyl-5-phenylthiophen-3-yl)-2-(2-methyl/methoxy-4-methylthiophen-3-yl)perfluorocyclopentenes (38-H-41-H). Regioselective synthesis of the 2-unsubstituted thiophenes 38-H-41-H required intermediate preparation of 2-trimethylsilyl-3,5-dimethyl-4-bromothiophene (37) or 2-trimethylsilyl-5-methoxy-3-methyl-4-bromothiophene (40). Protection of the alpha-position of the thiophene ring with a 2-trimethylsilyl group blocks the rearrangement of the 4-lithio derivatives into the corresponding 2-lithiated thiophenes. With the bicyclo[1.1.1]pentane fragment linking the photochromic units 1-3 and 1,5-dimethoxy-9,10-di(phenylethynyl)anthracene as a fluorescent part, quantitative resonance energy transfer between the excited state of the fluorophore (donor) and the closed form of the photochromic units 1-3 (acceptors) was observed. The closed forms of the methoxy-substituted photochromic units 2 and 3 are less resistant to UV light (313 nm) than the closed form of 1. |
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Keywords: | bicyclo[1.1.1]pentane fluorescence molecular switches photochromism thiophenes |
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