Mesomorphic behaviour and TSDC measurements of ortho-metallated palladium(II) and platinum(II) complexes with S,O-donor co-ligands

Abstract

A series of ortho-metallated Pd and Pt complexes containing an imine ligand carrying three alkoxy chains and N-benzoylthiourea derivatives as co-ligands were prepared and their liquid crystalline properties investigated. Their structures were assigned based on elemental analysis, IR and ¹H NMR spectroscopy, whereas thermal properties were investigated by differential scanning calotimetry and polarising optical microscopy. All the compounds exhibit monotropic transitions involving nematic and smectic A phases, with the mesomorphic behaviour strongly related to the type of N-benzoylthiourea as well as the metal centre used. The thermally stimulated depolarisation current technique was employed to determine the conduction mechanism, phase transition temperature and the activation energies for one of the ortho-metallated Pd complexes.

Keywords:

• palladium complex
• platinum complex
• ortho-metallation
• N-benzoylthiourea derivative
• TSDC

Aknowledgements

The authors wish to thank MEdC (Romanian Ministry of Education and Research, project CNCSIS-1640, project PNII ID_954 and project PNII ID_123) and NATO for funding this study and to Prof. Duncan W. Bruce (University of York, UK) for his support.