Ferromagnetically coupled CoII2LnIII2 complexes (where LnIII = Ho, Er, Yb): experimental and theoretical investigations.

A series of heterotetranuclear complexes [CoII2Ln2(HL)4(OAc)3(H2O)2]·(NO3)3 (where LnIII = Ho (1), Er (2) or Yb (3)) reported with a Schiff base (2-methoxy-6-[(E)-2′-hydroxymethyl-phenyliminomethyl]-phenol) ligand. The X-ray diffraction and structural solution confirmed the isostructural identity of 1 and 3. Complexes 1 and 3 were crystallized in a monoclinic crystal system having a C2/c space group, while complex 2 lacked X-ray quality crystals. The direct current (dc) magnetic measurements on complexes 1–3 indicate dominant intramolecular ferromagnetic interactions. The CASSCF/SO-RASSI/SINGLE_ANISO calculations followed by POLY_ANISO simulations were performed to understand the electronic structure, nature and strength of the CoII–LnIII and LnIII–LnIII magnetic exchange interactions, using the Molcas 8.0 program. To verify the nature of CoII–LnIII magnetic interactions, BS-DFT calculations were performed. The sign and the magnitude of the estimated JCo–Ln values show weak but dominant intramolecular ferromagnetic interactions between CoII and LnIII metal ions. In contrast, JLn–Ln values show the weak antiferromagnetic interactions between LnIII ions in complexes 1–3. [ABSTRACT FROM AUTHOR]