Gearing of Molecular Swirls: Columnar Packing of Nematogenic Hexakis(4-alkoxyphenylethynyl)benzene Derivatives

• Published in: Chemistry : a European journal Vol. 17; no. 3; pp. 792 - 799
• Main Authors: Lee, Shern-Long, Lin, Hsing-An, Lin, Yi-Hui, Chen, Hsiu-Hui, Liao, Ching-Ting, Lin, Tzu-Ling, Chu, Yi-Chen, Hsu, Hsiu-Fu, Chen, Chun-hsien, Lee, Jey-Jau, Hung, Wen-Yi, Liu, Qu-Yuan, Wu, Chunhung
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 17.01.2011; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chains; Chemistry; Chemistry, Multidisciplinary; Column packings; columnar suprastructures; Derivatives; Diffraction; helical structures; Hydrocarbons; liquid crystals; Molecular conformation; molecular swirls; Phases; Phenyls; Physical Sciences; Scanning; scanning tunnelling microscopy; Science & Technology; X-rays; scanning tunnelling microscopy; columnar suprastructures; INTERFACE; helical structures; molecular swirls; SCANNING-TUNNELING-MICROSCOPY; GRAPHITE; liquid crystals; DISCOTIC LIQUID-CRYSTALS; ALKYL CHAIN; HYDROCARBON
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201002975

Through molecular design and straightforward synthesis, incorporating an additional alkoxy chain onto various numbers of peripheral phenyls in nematogenic hexakis(4‐alkoxyphenylethynyl)benzene was achieved to generate columnar phases with significantly expanded temperature ranges. For the compound with two decyloxy chains on every peripheral phenyl, scanning tunnelling microscopic studies indicate the molecule adopts a preferred molecular‐swirl geometry by restricting the conformational arrangement of the alkoxy side chains. Cooperative packing of the molecular swirls by a lock‐in mechanism among columns results in a stable helical column packing evidenced by powder X‐ray diffraction. A swirling of the gears: With the new molecular swirl design based on a well‐known discotic nematogenic core, hexa(phenylethynyl)benzene, the cooperative packing of the molecular swirls by a lock‐in mechanism among columns revealed by STM studies has been utilised for the formation of a helical columnar mesophase corroborated by X‐ray diffraction investigations (see graphic).