Phase behaviour and magnetocaloric effect of poly(propylene imine) Iron(III) dendromesogen of the third generation

Abstract

ABSTRACT The dendritic iron (III) complex of the third generation (3-K2.10-(FeCl3)9) has been synthesised by complex formation between metal salt and organic ligand and studied. The structural characterisation and mesomorphic properties of the synthesised dendritic complex were investigated by FT-IR spectroscopy, X-ray diffraction measurements, polarising optical microscopy, and differential scanning calorimetry. It was shown that the given complex forms a columnar (Colh) mesophase with the transition to glass state upon cooling. The specific heat capacity of the complex was determined for the first time. The temperature dependencies of the specific heat capacity of the ligand and Fe(III) complex with the third-generation dendrimer show maxima that indicate a ‘crystal – mesophase’ transition. In order to determine the magnetocaloric effect, magnetisation experiments at fields from 0 to 1.0 T were performed from 263 to 358 К. The temperature dependence of the magnetocaloric effect is extreme. In the temperature range 340 – 350 К there is a sharp maximum indicating a magnetic phase transition. A correlation was found between the ‘crystal – mesophase’ transition and magnetic phase transition of the Fe(III) complex. The experimentally discovered fact of the existence of the liquid crystalline phase and the spin crossover in the same temperature region suggests the use of this compound in high-tech industries.