Ortho-platinated metallomesogens based on rod mesogenic unit of 2-phenylpyridine derivatives: synthesis, high linearly polarised and phase-state-dependent luminescence

Abstract

Three series of cyclometalated platinum (II) complexes [(cbCnppyC16) Pt(acac) (an), (cbCnppyC16)Pt(pic) (bn) and (cbCnppyC16)Pt(picd) (cn)] were obtained, where cbCnppyC16 (2-(4-hexadecyloxyphenyl)-5-[(1,1ʹ-biphenyl)-4-carbonitrile-4ʹ-alkoxy-methoxyl]pyridine) is as cyclometalated ligand, and Hacac (acetylacetone), Hpic (picolinic acid) and Hpicd (5-[(1,1ʹ-biphenyl)-4-carbonitrile-4ʹ-dodecyloxy]oxy-2-car boxylpyridine) are auxiliary, respectively. The liquid crystalline behaviour, polarised emission, photophysical and phase-state-dependent luminescence properties for all platinum (II) complexes were investigated systematically. Cyclometalated platinum (II) complexes bn show smectic phase structure; however, an and cn show nematic phase. The platinum (II) complexes exhibit different photoluminescence (PL) behaviour in solution, crystal phase, liquid crystal phase and amorphous thin films. Moreover, these metallomesogens show strongly polarised photouminescence in liquid crystalline phases. Especially, the PL dichroic ratio is up to 24.6 in nenatic phase.