Magnetocaloric behavior of REE porphyrin-based paramagnets at room temperature

Abstract

REE complexes with cyclic aromatic ligands are ranked as the molecular materials with both electronic functionality and a single-molecule magnet behavior at temperatures lower 80 K. At the temperature close to room, they display a positive magnetocaloric effect (MCE) often comparable with one in ferromagnetics. We were determined MCE during the magnetization of both (5,10,15,20-tetra(4-tert-butylphenylporphinato))ytterbium(III)chloride, (Cl)YbT[Formula: see text]BuPP and (5,10,15,20-tetraphenylporphinato)ytterbium(III)chloride, (Cl)YbTPP in their aqueous suspensions over the temperature range of 278–320 K and in magnetic fields from zero to 1 T by the direct microcalorimetric method. Specific heat capacity in the solid of (Cl)YbT[Formula: see text]BuPP/(Cl)YbTPP has been directly determined in zero magnetic fields using differential scanning calorimetry. Thermodynamic parameters of ytterbium(III) complexes magnetization namely enthalpy/entropy change was determined. To improve understanding of the correlation between (Cl)YbT[Formula: see text]BuPP/(Cl)YbTPP magnetic properties and its electronic structure, we have compared magnetic behavior of paramagnets studied with those for (Cl)MTPP where M = Gd, Eu, Tm.