Molecular paramagnets. The effect of structural modification on (porphyrinato) gadolinium(III) magnetothermal properties

Abstract

Depending on an axial ligand, paramagnetic rare earth porphyrin complexes show the magnetocaloric effect changed from 0.127 to 1.45K (“great magnetocaloric effect”) at the temperatures close to room when the magnetic field changes from 0 to 1.0T and thus are important candidates for new functional molecular materials in magnetic refrigeration and hyperthermia. Effect of extension of the π networks along axis perpendicular to the macrocycle plane due to chelating acetylacetone anion on a magnetic behaviour of gadolinium(III) porphyrin is presented in this work. Magnetothermal properties namely a specific heat capacity, a magnetocaloric effect, a heat released due to magnetocaloric effect, an enthalpy/entropy change of magnetization of 2.5% water suspensions of (5,10,15,20-tetraphenyl21H,23H-porphinato) gadolinium(III) acetylacetonate, (Acac)(AcacH)3GdTPP are studied as a function of both temperature and magnetic induction. Direct methods of the microcalorimetry and differential scanning calorimetry were used for the measuring of a magnetocaloric effect and a specific heat capacity, respectively. The effect of axial acetylacetonate on magnetothermal properties is discussed in comparison with the data for the axial acetate and chloride complexes in a view of optimization of magnetothermal properties for application in cooling and hyperthermia.