A synthetic strategy for switching the single ion anisotropy in tetrahedral Co(II) complexes.

Four novel mononuclear tetrahedral cobalt(II) complexes containing exocyclic mesoionic ligands of molecular formulae [Co(II)(L1)(X)2(MeCN)] X = Cl (1) or Br (2) and [Co(II)(L2)(X)2(MeCN)], X = Cl (3) or Br (4) have been reported. It is found that simple substitution of L1 (O donor in 1 and 2) by L2 (S donor in 3 and 4) results in switching of the single ion magnetic anisotropy parameter (D) from positive to negative, with a significant change in magnitude.