The Organic Ammonium Counterion Effect on Slow Magnetic Relaxation of the [Er(hfac)₄]^- Complexes

The first mononuclear anionic erbium complex [Er(hfac)(4)](-) (hfac = hexafluoroacetylacetone) with an organic ammonium cation [(CH3)(4)N+] as the counterion was synthesized and structurally and magnetically characterized. The coordination geometries around the Er ions are square antiprisms with pseudo-D-4d symmetry. The complex shows distinct field-induced slow magnetization relaxation, which is described by a combination of Orbach (U-eff/k(B)similar to 28.54(8) K.) and direct mechanisms. Quantum chemical calculations were performed to analyze the magnetic properties of the complex under consideration.