Cubane lanthanoid complexes with tridentate [O, P=O, O] coordination using tris(5-tert-butyl-2-hydroxyphenyl)-phosphine oxide ligands: synthesis, characterisation, and magnetic behaviour

Abstract

Functionalised ortho-aryl phosphine oxides are assessed as candidates for lanthanoid (Ln) coordination. The series of tetranuclear Ln complexes synthesised [{Ho(μ3-OH)(μ2,κ3-LH)(C2H5OH)}4] (1), [{Dy(μ3-OH)(μ2,κ3-LH)(C2H5OH)}3{Dy(μ3-OH)((μ2,κ3-LH)(H2O)}]·5(EtOH) (2) and [{Tb(μ3-OH)(μ2,κ3-LH)(C2H5OH)}4]·4.8(EtOH) (3) with ligand tris(5-tert-butyl-2-hydroxyphenyl)-phosphine oxide (LH3) highlight that these are a promising ligand class. The distorted cubane Ln4 complexes were generated by ensuring appropriate functionalisation of an ortho-aryl phosphine oxide ligand to balanced the reactivity and solubility of reactants to generate these unique compounds. DC magnetic studies for 1 and 2 reveal that complexes support weak antiferromagnetic coupling between the centres, with 2 exhibiting a frequency dependence in the zero field out-of-phase component of the AC susceptibility.