Synthesis and Mesomorphic Properties of Multiynylthiophenes: 2,3,4,5-Tetrakis(4-alkoxyphenylethynyl)thiophenes and 2,3,5-Tris(4-alkoxyphenylethynyl)thiophenes

The synthesis and characterization of multiynylthiophenes, tetrakis(4-alkoxyphenylethynyl)thiophenes ( 1 ) and tris(4-alkoxyphenylethynyl)thiophenes ( 2 ), are reported, and their structure−mesomorphism relationship is discussed. The tetraynyl series 1 with a trapezoid core do not show any liquid-crystalline properties. With one less peripheral arm, series 2 compounds are of the Y-shape geometry with rigid linear spacers and nematic phases are observed for the octyloxyl, decyloxyl, and dodecyloxyl derivatives. Although the dipole−dipole interactions, desymmetrization, and disparity of the mesogenic cores can be accountable for their corresponding mesomorphic behaviors, the formation of the nematic phases of 2 may be most likely attributed to the shape disparity of these two series of compounds.