Magnetic on–off switching in redox non-innocent ligand bridged binuclear cobalt complexes

Abstract

The redox non-innocent ligand 2,2′-bipyrimidine (bpym) reacted with two molar equivalents of LCo(tol) (L = CH(MeCNAr)₂, Ar = 2,6-iPr₂C₆H₃) to afford the binuclear Co^II complex (LCo)₂(μ-bpym) (1), in which the bpym moiety accepts two electrons from the metal centers and in the dianion state. Complex 1 readily underwent one-electron oxidation when treated with [Cp₂Fe]⁺[BPh₄]⁻ affording the cation salt [(LCo)₂(μ-bpym)][BPh₄] (2) with the bpym moiety in the radical anion state. Meanwhile, complex 2 could be converted back to 1 with elemental potassium. The magnetic studies revealed that complex 2 is a single molecular magnet (SMM) under a small external field, while 1 has no SMM activity. This represents a new example of a SMM exhibiting a fully reversible ‘on/off’ switching ability in anodic and neutral states.