Dinuclear ortho-Metallated Palladium(II) Complexes with Acetato and Chloro Bridges as Liquid Crystals

Abstract

In this article we present the preparation and the investigation of the liquid crystal properties of a series of dinuclear acetato- and chloro-bridged ortho-metallated Pd(II) complexes bearing six alkoxy peripheral chains in the molecule. Their structures were assigned based on elemental analysis, Infrared (IR), and ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, whereas the thermal behavior was investigated by polarizing optical microscopy and differential scanning calorimetry. All these complexes show mesomorphic behavior with smectic A phases being displayed. The acetato complexes exhibit a monotropic smectic A phase with transition temperatures from the isotropic state depending on the alkyl chain lengths, whereas the chloro complexes decompose on melting from the crystalline state to an SmA phase.

Keywords:

• Liquid crystals
• metallomesogens
• orthometallation
• palladium
• smectic

Acknowledgments

The authors acknowledge the financial support from CNCSIS-UEFISCSU, project number PNII-IDEI ID_954/2007 and CNCSIS A1640_GR 96/2007.