Tetraphenylethene-Derived Columnar Liquid Crystals and Their Oxidative Photocyclization

✍ Scribed by Andreas Schultz; Sabine Laschat; Siegmar Diele; Manfred Nimtz

• Book ID: 102827266
• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 570 KB
• Volume: 2003
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200300118

✦ Synopsis

Abstract

The synthesis of novel tetraphenylethenes 9a−f, 13, and 18a,b bearing ether, biphenyl, and 4‐cyanobiphenyl moieties via a McMurry reaction and Suzuki coupling as key steps is described. Mesogenic properties of these compounds were studied by differential scanning calorimetry (DSC), optical polarizing microscopy, and X‐ray diffraction. Ether‐substituted derivatives 9a,b with chain lengths C~8~ or C~9~ were non‐mesogenic. Compounds 9c−f with longer alkyl chains displayed hexagonal columnar mesophases. Whereas cyanobiphenyl derivative 13 was non‐mesogenic, the corresponding biphenyl systems 18a,b with decyloxy and dodecyloxy chains, respectively, formed hexagonal columnar mesophases. Oxidative photocyclization of compounds 1f, 9c, 13, and 18a were investigated. Upon irradiation in the presence of iodine tetraphenylethenes 1f, 9c gave the corresponding phenanthrenes 22a,b. The mesomorphic properties of 22a,b were strongly dependent on the substituent. Whereas ether 22a displayed only isotropic melting, a hexagonal columnar mesophase was found for ester 22b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)