Two Tetranuclear Butterfly-Shaped Co(II) Complexes: Structure, Mass Spectrometric, and Magnetism

Abstract

The organic ligand (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (HL) was used to react with CoX2·6H2O (X = Cl and Br) under solvothermal conditions to obtain the complex [Co4(L)6(X)2] (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 O3NX environment and six coordination with O4N2 environment. In addition, the electrospray ionization mass spectrometry (ESI-MS) analysis indicated that the ion molecular fragment of highest intensity was [Co4(L)6]2+, and there existed a high nuclear fragment peak of [Co7(L)12]2+. Interestingly, it was basically completely transformed into [Co7(L)12]2+ two days later, so those two complexes were relatively stable in CH3OH. Magnetic characterization exhibited that complex 1 and 2 display field-induced single-molecule magnetic behavior, of which the energy hills Ueff/kB were 28 and 20 K under direct-current field of 0.1 T, respectively.