Mixed-metal single-molecule magnets: Syntheses, structure, and magnetic properties of [Mn8Fe4O12(O2CR)16(H2O)4] (R = CH2Cl, CH2Br, CHCl2)

Three mixed-metal single-molecule magnets containing [Mn8Fe4O12]16+ cores are synthesized and characterized. The reaction of FeCl2·4H2O with KMnO4 and RCOOH (R = CH2Cl, CH2Br) in H2O gives [Mn8Fe4O12(O2CR)16(H2O)4] (R = CH2Cl (1), CH2Br (2)) in yields of 43% and 40%, respectively. Treatment of complex 1 with an excess of CHCl2COOH in CH2Cl2 gives [Mn8Fe4O12(O2CCHCl2)16(H2O)4]·CH2Cl2·10H2O (3·CH2Cl2·10H2O) in a yield of 83%. The X-ray structure analysis reveals that all three complexes consist of a trapped-valence dodecanuclear core comprising 4MnIII, 4FeIII, and 4MnIV ions. DC magnetic susceptibility and magnetization measurements indicate that all three complexes exhibit intramolecular antiferromagnetic interaction, resulting in an S = 4 ground state. In addition, frequency-dependent out-of-phase AC magnetic susceptibility signals at low temperature for complexes 1, 2, and 3 are indicative of their single-molecule magnetism behavior.

Graphical abstractThree mixed-metal dodecanuclear complexes, [Mn8Fe4O12(O2CR)16(H2O)4] (R = CH2Cl, CH2Br and CHCl2), have been synthesized and characterized structurally as a [Mn8Fe4O12]16+ core. Magnetic data analysis shows that all of the three complexes are antiferromagnetic with a ground state of S = 4. The frequency-dependent out-of-phase AC magnetic susceptibility signals at low temperature for these three complexes indicate their single-molecule magnet properties.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Three Mn8Fe4 dodecanuclear complexes have been synthesized and characterized structurally. ► All of the three complexes are antiferromagnetic with the ground state of S = 4. ► They exhibit many processes relaxations shown in the out-of-phase AC magnetic susceptibility signals.