Heptanuclear cobalt(II) dicubane compounds with single-molecule magnet behavior

• Two heptanuclear cobalt(II) compounds were synthesized and characterized.
• Crystal structures consist of two cubane-like units linked by one shared CoII vertex.
• Compounds present single-molecule magnet behavior.

The reaction between the tetranuclear compound [Co4(tta)4(OMe)4(MeOH)4] (tta = 4,4,4-trifluoro-1-thienoyl-2,4-butanedionate) and isopropanol or n-butanol leads to two heptanuclear compounds with general molecular formula [Co7(OH)8(tta)6(ROH)6]·ROH (R = isopropyl, for 1 or n-butyl, for 2). The crystal structures of both heptamers consist of two cubane-like units linked through one shared cobalt(II) ion vertex. The reaction leads to the replacement of precursor methoxide bridges by hydroxo in the heptanuclear compounds, which connect the internal metal ion to the six external ones. The magnetic properties revealed moderate ferromagnetic interactions among the cobalt(II) ions. Furthermore, ac magnetic susceptibility measurements confirm that these compounds are new examples of single-molecule magnets (SMM) containing cobalt(II) ions, with an energy barrier for magnetization reversal of 22 K and 21 K, respectively for 1 and 2.

The reaction between isopropanol or n-butanol and the tetranuclear precursor [Co4(tta)4(OMe)4(MeOH)4] (tta = 4,4,4-trifluoro-1-thienoyl-2,4-butanedionate) leads to two heptanuclear compounds with general molecular formula [Co7(OH)8(tta)6(ROH)6]·ROH (R = isopropyl or n-butyl). Moderate ferromagnetic interactions are present in both compounds. Ac magnetic measurements revealed that these compounds behave as single-molecule magnets at low temperatures.Figure optionsDownload as PowerPoint slide