Smectic phases of liquid crystals based on dinuclear palladium(II) complexes with carboxylato bridge

Abstract

In this paper we present the preparation and the investigation of the liquid crystal properties of a series of dinuclear carboxylato bridge Pd(II) complexes bearing six alkoxy peripheral chains in the molecule. Their structures were assigned based on elemental analysis, IR and 1 H NMR spectroscopy whereas the thermal behaviour was investigated by polarizing optical microscopy and differential scanning calorimetry. The monotropic smectic A phase displayed by these materials was identified by miscibility studies with a previously reported mesogen. It was found that the transition temperatures and the SmA mesophase stability depend on the alkyl chain length of the carboxylato bridge.

Organometallic Mesogens

“…The substitution of the azo group by a decyloxy tail in the biscarboxylato bridges, together with the incorporation of a second alkoxy substituent in the metalated aromatic ring, 98, give rise to the appearance mainly of monotropic SmA mesophases. 144 The same behavior has been found for related dinuclear acetate complexes. 145 Mono and dinuclear triphenylene-imine ortho-palladated complexes 99 have also been prepared showing unusual columnar mesophases near room temperature.…”