title: Triphenylene discotic liquid crystal trimers synthesized by Co2(CO)8-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition.
abstract: The synthesis of star-shaped discotic liquid crystal trimers using Co2(CO)8-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition reaction is reported. The trimers consist of three triphenylene discotic units linked to a central 1,2,4-trisubstituted benzene ring via flexible spacers. The trimers were synthesized in the yields up to 70% by mixing the monomers with 10 mol % of Co2(CO)8 as the catalyst in refluxing 1,4-dioxane. The liquid crystalline properties were investigated by using polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Trimer 4 with an ester connecting group and a longer spacer exhibited a rectangular columnar mesophase, while 5b and 5c possessing an ether linkage and a shorter spacer display a hexagonal columnar mesophase. The connecting functional group and the length of the flexible spacer between the central benzene ring and the triphenylene units have pivotal influence on the mesomorphism.
authors.affiliation: College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Han
authors.affiliation: College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Hu
authors.affiliation: College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China.
authors.forename: Bi-Qin
authors.initials: BQ
authors.lastname: Wang
authors.affiliation: College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China ; Department of Chemistry, University of Hull, Hull, HU6 7RX, UK.
authors.forename: Carl
authors.initials: C
authors.lastname: Redshaw
authors.affiliation: College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China.
authors.forename: Ke-Qing
authors.initials: KQ
authors.lastname: Zhao
keywords: Co2(CO)8 catalyzed cycloaddition; columnar mesophase; discotic liquid crystal; oligomer; triphenylene