TY - JOUR A1 - Han, Bin A1 - Hu, Ping A1 - Wang, Bi-Qin A1 - Redshaw, Carl A1 - Zhao, Ke-Qing T1 - Triphenylene discotic liquid crystal trimers synthesized by Co2(CO)8-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition JF - Beilstein Journal of Organic Chemistry PY - 2013/// VL - 9 SP - 2852 EP - 2861 SN - 1860-5397 DO - 10.3762/bjoc.9.321 PB - Beilstein-Institut JA - Beilstein J. Org. Chem. UR - https://doi.org/10.3762/bjoc.9.321 KW - Co2(CO)8 catalyzed cycloaddition KW - columnar mesophase KW - discotic liquid crystal KW - triphenylene KW - oligomer N2 - 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. ER -