A Multifaceted Cage Cluster, [CoII 6O12 ⊃ X]− (X = Cl− or F−): Halide Template Effect and Frustrated Magnetism

Two hexanuclear CoII clusters, NHEt3[Co6(phendc)6 ⊃ X]·MeOH·3H2O (X = Cl− (1) or F− (2)), were obtained accidently by the in situ formation of the coordinating ligand H2phendc (1,10-phenanthroline-2,9-dicarboxylate) from the precursor ligand H2phenox (1,10-phenanthroline-2,9-dicarbaldehyde dioxime). Halides among the reactants used become the template around which a highly symmetric cluster is generated which display spin-glass magnetic behavior as a consequence of the severe magnetic frustration due to geometrical arrangement of the moments. Different anion-template effects were demonstrated by ESI-MS studies. Interestingly, 1 exists in solution; in its solid state, a rare and unique single-crystal to single-crystal transformation is observed upon desolvation, which is accompanied by the departure of NEt3. Both dc and ac magnetization data suggest the spin-glass behavior for 1 and its guest-free structure H[Co6(phendc)6Cl] (1′) at different blocking temperatures of 5.3 and 7.8 K, respectively. The absence of this observation for 2 raises an interesting question regarding its origin and provides a remarkable example of fine-tuning of frustrated magnetic properties via host−guest interactions.