Equatorial Coordination Optimization for Enhanced Axiality of Mononuclear Dy(III) Single-Molecule Magnets
We present a controlled synthetic route to operate the equatorial coordination environment of three Dy(III) borohydrides complexes: Dy(BH4)3(THF)3 (1), [Dy(BH4)2(THF)5][BPh4] (2) and [Dy(BH4)2(18-C-6)][Na(THF)2(18-C-6)][BPh4]2 (3) (THF = tetrahydrofuran, BPh4– = tetraphenyl borate, 18-C-6 = 18-crown-6-ether), which have the same axial coordination environment while different equatorial sites. Such an alternation leads to a significant change of magnetic properties. In the absence of dc field, complex 1 with three THF molecules and one BH4– ligand in the equatorial plane shows no single-molecule magnet (SMM) behaviour, complex 2 having five THF molecules at equatorial sites displays small tails of out-of-phase (χ") signals, and complex 3 containing one 18-C-6 with six O atoms in the equatorial plane exhibits χ" signals at higher temperatures. This result represents an optimaization of equatorial coordination environment for Dy(III) mononuclear single-molecule magnets.