Synthesis, linear dichroism and mesogenic properties of substituted azulenes

New liquid-crystalline azulenes exhibiting nematic phases and containing various substituents at one or more of the 1-, 2-, 3- and 6-positions are described. The linear dichroism of two derivatives is reported; one possesses a negative anisotropy and the other a positive anisotropy, owing to the influence of different substituents. The potential of the azulene ring as a core or subunit in mesogenic molecules is discussed.