Two macromolecular complexes derived from poly(propylene imine) with Co(II) and Ni(II) ions have been synthesized by direct complexation between metal salts and the second generation dendrimers. Based on experimental data one can assume the formation of a binuclear complex in the case of Co2+ while the Ni2+ complex is characterized by the filling of all possible coordination sites. Magnetocaloric behaviour of symmetric Co(II) and Ni(II) complexes was found. It has been established that when the synthesized samples are exposed to a magnetic field, the sign of the specific amount of heat (QMCE) changes. Analyzing the obtained data on the magnetocaloric effect of the complexes, it was shown that the MCE values are changed from the negative value ΔT (Co(II)) = -0.016 K, ΔT (Ni(II)) = -0.005 K to positive ΔT (Co(II)) = 0.011 K, ΔT (Ni(II)) = 0.002 K (at T = 337 K and 1 T). The presence of a maximum in the temperature dependences of the heat capacity indicates a second-order phase transition. It was found for the studied complexes that they exhibit enantiotropic mesomorphism with the formation of columnar phases.
