Magneto-Optical Correlations in a High Symmetry Dysprosium Complex Reveal an Almost “Ideal Non-SMM” and Orange-to-Red DyIII-Based Emitter

Abstract

The importance of investigating high-symmetry systems in order to reveal properties that would otherwise be concealed in less symmetrical compounds is demonstrated. This is particularly true for discrete coordination complexes that tend to adopt low symmetries. The magnetic, optical, and theoretical investigation of [Dy{N(SiMe₃)₂}₃], an amido complex that features an almost trigonal electrostatic environment around the Dy^III ion, is reported here. While this specific coordination is ideally suited to the stabilization of high magnetic ground state for “prolate” Yb^III-based single-molecule magnet (SMM), it is the opposite for oblate Dy^III. Hence, [Dy{N(SiMe₃)₂}₃] is expected to display the lowest conceivable magnetic anisotropy. This is confirmed herein by magneto-optical and theoretical correlations. An extremely pure Kramers doublet composition is observed on a totally reversed energetic profile compared to the standard Dy^III-SMM. This results in a paramagnetic but dynamically silent compound, even when an external dc field is applied. Additionally, this unusual energetic profile induces an exceptional optical signature, with orange (300 K) to red (4 K) emission, far from the traditional white-to-yellow emission expected for a Dy^III ion.