Imidazo [2, 1-b]-1,3,4-thiadiazoles. A new class of liquid-crystalline compounds

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 (T_c1 ∼ 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.