A Multifaceted Cage Cluster, [Co^II₆O₁₂ ⊃ X]⁻ (X = Cl⁻ or F⁻): Halide Template Effect and Frustrated Magnetism

Two hexanuclear Co II clusters, NHEt 3 [Co 6 (phendc) 6 ⊃ X]·MeOH·3H 2 O (X = Cl − ( 1 ) or F − ( 2 )), were obtained accidently by the in situ formation of the coordinating ligand H 2 phendc (1,10-phenanthroline-2,9-dicarboxylate) from the precursor ligand H 2 phenox (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 NEt 3 . Both dc and ac magnetization data suggest the spin-glass behavior for 1 and its guest-free structure H[Co 6 (phendc) 6 Cl] ( 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.