Vadapalli Chandrasekhar, Indian Institute of Technology, Kanpur, and colleagues assembled a new family of pentanuclear heterobimetalllic compounds [Co₄Ln(L)₄(OAc)₂(S)₄](NO₃)(S) [Ln^III = Gd^III, S = MeOH (1); Ln^III = Dy^III, S = H₂O (2); Ln^III = Tb^III, S = MeOH (3); Ln^III = Ho^III, S = MeOH (4)]. The core of these complexes is made up of a distorted Co₄ tetrahedron. The centre of the core contains the lanthanide ion (pictured). It is connected to the cobalt ions through the phenolate and [–CH₂O]– parts of the ligand.

For (1)–(4), the magnetic coupling between the Co^II ions through the acetate bridge is antiferromagnetic, whereas the interaction between the Co^II ions and the corresponding Ln^III ion can be considered negligible. This indicates that the overall magnetic properties of this family of compounds are dominated by the crystal field effects of the lanthanide(III) ions (2)–(4) and the antiferromagnetic coupling of the cobalt(II) ions (1)–(4).

The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol (LH₂) with appropriate lanthanide salts followed by the reaction with Co(OAc)₂•4H₂O resulted in the pentanuclear heterobimetalllic compounds (1)–(4) in good yields. All the compounds are stable in solution as confirmed by ESI-MS studies.

• Synthesis, Structure, and Magnetic Properties of a Family of Heterometallic Pentanuclear [Co₄Ln] (Ln = Gd^III, Dy^III, Tb^III, and Ho^III) Assemblies,
  Vadapalli Chandrasekhar, Sourav Das, Atanu Dey, Sakiat Hossain, Francesc Lloret, Emilio Pardo,
  Eur. J. Inorg. Chem. 2013.
  DOI: 10.1002/ejic.201300413