| Summary: | The organic ligand (1-methyl-1<i>H</i>-benzo[<i>d</i>]imidazol-2-yl)methanol (HL) was used to react with CoX<sub>2</sub>·6H<sub>2</sub>O (X = Cl and Br) under solvothermal conditions to obtain the complex [Co<sub>4</sub>(L)<sub>6</sub>(X)<sub>2</sub>] (1, X = Cl; 2, X = Br). The butterfly-shaped structure of complex 1 and 2 suggest that Co(II) ions have two different coordinated modes, which are five coordination with O<sub>3</sub>NX environment and six coordination with O<sub>4</sub>N<sub>2</sub> environment. In addition, the electrospray ionization mass spectrometry (ESI-MS) analysis indicated that the ion molecular fragment of highest intensity was [Co<sub>4</sub>(L)<sub>6</sub>]<sup>2+</sup>, and there existed a high nuclear fragment peak of [Co<sub>7</sub>(L)<sub>12</sub>]<sup>2+</sup>. Interestingly, it was basically completely transformed into [Co<sub>7</sub>(L)<sub>12</sub>]<sup>2+</sup> two days later, so those two complexes were relatively stable in CH<sub>3</sub>OH. Magnetic characterization exhibited that complex 1 and 2 display field-induced single-molecule magnetic behavior, of which the energy hills <i>U</i><sub>eff</sub>/<i>k</i><sub>B</sub> were 28 and 20 K under direct-current field of 0.1 T, respectively.
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