Magnetocaloric effect and heat capacity of ferrimagnetic nanosystems: Magnetite-based magnetic liquids and suspensions

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

“…The appearance of MCE in high spin porphyrin complexes was for the first time observed in [5] for the example of (2,3,7,8,12,13,17,18 octaethylpor phynato)chloromanganese(III) (Cl)MnOEP. In [6], an attempt was made to study the influence of the structure of the mixed five coordinate node in com plexes with 5,10,15,20 tetraphenylporphin having the general formula (X) n -2 TPP, where X -and TPP 2-are the acido and porphyrin ligands, respectively, on MCE and other magnetothermal properties.…”

“…In this work, we continue our studies by determin ing the magnetocaloric effect, heat capacity, and enthalpy and entropy of magnetization for the high spin (acetato) (2,3,7,8,12,13,17,18 octa para tert butylphenyltetraazaporphynato)manganese(III) com plex at 298 K, R = p t BuPh; (AcO)Mn(p t BuPh) 8 8 TAP was prepared by cyclic tetramerization of bis(o tert butylphenyl)fumaronitrile in the presence of a manganese salt. Bis(para tert butylphenyl)fuma ronitrile (1 g, 2.91 mmol) and Mn(OAc) 2 · 4H 2 O (0.85 g, 3.48 mmol) were gradually heated to 423 K in 2 dimethylaminoethanol (7 mL) under stirring and held for 10 h. The consumption of nitrile was moni tored using thin layer chromatography (TLC).…”

“…Interest in MCE is related to the possibility of obtaining information about the nature of the magneti cally ordered state. When a magnetic field is applied to a magnet, the heat capacity also changes, and the heat capacity is the most important parameter necessary for calculations of many thermodynamic values, such as, for instance, magnetic entropy [2][3][4]. Magnetic entropy data also allow us to draw conclusions about magnetic ordering in magnetoactive substances.…”

“…The complex was purified chromatographi cally (silica gel, CHCl 3 -1% CH 3 OH) and dried in a vacuum (0.1 bar, 333 K, 24 h). The yield was 0.52 g (48% MCE and heat capacity measurements for aqueous suspensions of the high spin manganese complex were performed on an automated microcalorimetric unit [7]. The measuring microcalorimetric cell with an iso thermic shell was placed into an interpole gap of an electromagnet.…”

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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 octaethylpor phynato)chloromagnanese(III) studied earlier. High dispersity complex particles were found to have para magnetic properties.

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