The magnetothermal properties of substituted (tetraazoporphynato)manganese(III) in aqueous suspension

Abstract

The magnetocaloric effect (MCE), heat capacity, and enthalpy and entropy of magnetization of the high-spin (acetato)(2,3,7,8,12,13,17,18-octa-para-tert-butylphenyltetraazaporphynato)manganese(III) complex in a 6% aqueous suspension were determined microcalorimetrically at 298 K in magnetic fields of 0.1–1.0 T, that is, under the conditions comparable with those used with (2,3,7,8,12,13,17,18-octaethylporphynato)chloromagnanese(III) studied earlier. High-dispersity complex particles were found to have paramagnetic properties. Positive MCE values were obtained. These values grew as magnetic field induction increased. MCE sensitivity to the nature and electronic structure of the aromatic macroring was studied. The presence of aza groups in the structure of the complex decreases the MCE value compared with the porphyrin complex. The specific heat capacity of the complex strongly depended on the magnetic field value; field dependences had a maximum close to 0.3 T. Changes in the ΔSm(H, T) molar entropy part were also extremal and had maxima at 0.3–0.4 T. Prospects for the use of magnetothermal properties in the quantitative determination of thermodynamic characteristics and for revealing trends of changes in the magnetic activity of porphyrin complexes are discussed.