Mesogenic binuclear oxamide derivatives with discotic and calamitic properties

Abstract

Series of binuclear copper and nickel complexes having two tetradental enaminoketone centres have been synthesized and examined. The rectangular shape of the mesogenic core allows the formation of lamellar (SmA) or columnar (Col_h, Col_r) phases depending on the number of attached aliphatic chains. In some complexes the columnar phases have molecules tilted in columns. An unexpected phase sequence Col_r upper–Col_h–Col_r lower, upon lowering temperature, was detected, which is a type of re-entrancy. The crystallographic unit cells of the rectangular columnar phases are not the same. Intramolecular interaction between metallic centres was found in ESR studies and confirmed by cyclic voltammetry.