A series of new liquid-crystalline compounds called imidazo [2,1-b]-1,3,4-thiadiazoles has been synthesized. The new compounds contain alkyl, aryl, trans-alkylcyclohexyl groups in positions 2,6 and lateral Br- and CN-substituents in position 5 of the heterocyclic fragment. The new mesogens normally have a wide mesophase range and a high thermal stability (Tc1 ∼ 300° C). The mesophase type depends significantly on the nature and position of the substituents, in particular the cyclohexane ring. Some chemical, physico-chemical and spectral properties of the new compounds have been investigated. The results are compared with the corresponding characteristics of their aromatic and heterocyclic analogues.

A number of benzo/1,2-d:5, 4-d′/bisoxazoles have been synthesized. Only derivatives containing a cyclohexane ring exhibit liquid crystalline phases.

AbstractThe dielectric properties of the title compounds (IV), (VI) and (VII) in a liquid‐crystalline matrix are investigated.

AbstractThe 2,6‐disubstituted imidazothiadiazoles (IIIa)‐(IIId), which bear no substituent at C‐5, generally form smectic mesophases over a wide range of temperature.

AbstractThe novel title compounds (V) form smectic mesophases over a wide range of temperature.

A new series of liquid-crystalline materials containing the tricycle (4.4.0.03,8)-decane (twistane) and further examples of materials containing the spiro (3,3) heptane system have been prepared and their thermal properties examined. The mesomorphic properties are compared with those of the benzene, trans-cyclohexane and bicycle (2.2.2) octane derivatives. The replacement of the benzene ring in related compounds by the twistane ring results in a lowering of the melting and the clearing points as well as a narrowing of the mesophase interval. The esters of spiro (3, 3) heptane prepared exhibit smectic mesophases with a narrow temperature interval.

AbstractThe title compounds (I) dimerize in the presence of basic catalysts to form the aminocyclohexadienes (IIa) and (IIb).