Influence of the chain length on the thermal behavior of lanthanide(III) 4-alkoxybenzoates

4-Alkoxybenzoic acids are well-known liquid crystals. The rigid core of the mesogen is formed by intermolecular hydrogen bonds. Layered structures with characteristics that depend on the lanthanide ion are formed when a trivalent lanthanide ion is introduced. Also, the chain length influences the structure and hence the thermal behavior of these complexes. Lanthanide complexes of 4-butyloxybenzoic acid have a low crystallinity, whereas metal complexes with longer chain lengths display several types of layered structures. The thermal behavior of lanthanum(III) and holmium(III) 4-butyloxybenzoate, 4-hexyloxybenzoate, 4-octyloxybenzoate, 4-nonyloxybenzoate, and 4-decyloxybenzoate is discussed, relying on differential scanning calorimetry (DSC), thermooptical microscopy, and synchrotron X-ray diffraction data. A smectic A mesophase was observed for lanthanum(III) 4-hexyloxybenzoate, lanthanum(III) 4-octyloxybenzoate, and lanthanum(III) 4-nonyloxybenzoate. The corresponding holmium(III) compounds are not liquid crystalline.