Author:

Keywords:

liquid crystals, metallomesogens

Abstract:

By serendipity, we discovered that Lewis base adducts of tris(β-diketonato)lanthanide(III) complexes with a salicylaldimine Schiff’s base (L) have mesomorphic properties [1]. We used 1,3-diphenyl-1,3-propanedione (dibenzoyl-methane, Hdbm) as the β-diketone ligand and the ligand with one aromatic ring as the Schiff’s base. These ligands were already described for the formation of liquid crystalline lanthanide complexes [2]. In these compounds, neither the Schiff’s base nor the tris(β-diketonato)lanthanide(III) complex do exhibit a mesophase, but the resulting bisadducts are liquid-crystalline. These compounds are structurally and thermally characterized. The crystal structure of an adduct of a Schiff’s base with short alkyl chains to La(dbm)3 is described. The solution structure of diamagnetic complexes is investigated by 1D and 2D 1H-NMR methods. A series of compounds are prepared in order to investigate the influence of the lanthanide ion and the chain length on the thermal properties. The thermal behaviour of the lanthanide complexes is investigated by polarising optical microscopy (POM), differential scanning calorimetry (DSC) and by time-resolved temperature-dependent synchrotron X-ray diffraction measurements at the DUBBLE-beamline of the ESRF (Grenoble, France). [1] K. Binnemans, K. Lodewyckx; Angew. Chem. Int. Ed. 2001, 40, 242. [2] K. Binnemans, C. Görller-Walrand; Chem. Rev. 2002, 102, 2303.