Flying-seed-like liquid crystals 2: unprecedented guidelines to obtain liquid crystalline compounds

Abstract

In order to obtain novel “flying-seed-like” liquid crystals, we have prepared a series of bulky group-substituted phthalocyanine derivatives without any long alkyl chains: tetra[4-(triphenylmethyl)-phenoxy]phthalocyaninato copper(II) (1a), tetra[4-(1,1-diphenylethyl)phenoxy]phthalocyaninato copper(II) (1b), tetra[4-(1-methyl-1-phenylethyl)phenoxy]phthalocyaninato copper(II) (1c), tetra[4-(tert-butyl)phenoxy]phthalocyaninato copper(II) (1d), and octa[4-(triphenylmethyl)phenoxy]phthalocyaninato copper(II) (4). We have established by using a polarizing optical microscope, a differential scanning calorimeter and a temperature-dependent small angle X-ray diffractometer that the Pc derivatives 1a–d, but not 4, show columnar mesomorphism from r.t. to the extremely high decomposition temperatures at 450–500 °C. Their mesomorphism originates from thermal fluctuations due to free rotation of the bulky substituents. Thus, we have systematically demonstrated for the first time that liquid crystals can be also obtained by a series of novel bulky substituents instead of conventional long alkyl chains. Hence, we will be able to obtain a wide variety of new liquid crystalline compounds by using these bulky substituents instead of long alkyl chains. Very interestingly, these are unprecedented guidelines to obtain liquid crystalline compounds.