A series of bis(imidazolium) salts with different mesogenic groups (cyanobiphenyl or cholesteryl) and their silver carbene complexes with Branion has been designed and prepared. The liquid crystalline behaviour of these ionic liquids and their corresponding silver-carbene complexes was investigated by polarised optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis (TGA). The silver 10 complexes are thermally stable on a broad temperature range with accessible transition temperatures close to ambient temperature. The compounds having cholesteryl groups show higher transition temperatures than the compounds possessing cyanobiphenyl mesogenic groups, but their thermal stability is limited by a slight decomposition before reaching the isotropic state. Interestingly, the bis(imidazolium) salt with two cyanobiphenyl gropus at each side shows an enatiotropic nematic phase on a short range, being one 15 of the fewest example of ILC displaying nematic phases.

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In this work we report our studies concerning the synthesis and characterisation of a series of imine derivatives that incorporate the 2-phenylpyridine (2-ppy) core. These derivatives were used in the cyclometalating reactions of platinum(II) or palladium(II) in order to prepare several complexes with liquid crystalline properties. Depending on the starting materials used as well as the solvents employed, different metal complexes were obtained, some of them showing both liquid crystalline behaviour and luminescence properties at room temperature. It was found that, even if there are two competing coordination sites, the cyclometalation process takes place always at the 2-ppy core with (for Pt) or without (for Pd) the imine bond cleavage. We successfully showed that it is possible to prepare emissive room temperature liquid crystalline materials based on double cyclopalladated heteroleptic complexes by varying the volume fraction of the long flexible alkyl tails on the ancillary benzoylthiourea (BTU) ligands.