Identical anomalous Raman relaxation exponent in a family of Single Ion Magnets: towards reliable Raman relaxation determination?

Propeller-like lanthanide complexes with suitable chiral ligand scaffolds are highly desired as they combine chirality and magnetic bistability. However, the library of relevant chiral molecules is quite limited. Herein we present the preparation, structures, magnetic behavior as well as EPR studies of a series of propeller-shaped lanthanide Single Ion Magnets (SIMs). Coordination of the smallest helicene-type molecule 1,10-phenanthroline-N,N’-dioxide (phendo) to LnIII ions results in the formation of homoleptic complexes [LnIII(phendo)4](NO3)3∙xMeOH (Ln = Gd, Er, Yb) Gd, Er and Yb, where four phendos encircle the metal center equatorially in a four-bladed propeller fashion. The magnetization dynamics in these systems is studied by magnetic measurements and EPR spectroscopy for non-diluted as well as solid state dilutions of Er and Yb in a diamagnetic [YIII(phendo)4](NO3)3∙xMeOH (Y) matrix. Careful analysis of the slow magnetic relaxation in the diluted samples can be described by a combination of Raman and Orbach relaxation mechanisms. The most important finding concerns the identical power law τ ≈ T -3 describing the anomalous Raman relaxation for all three reported compounds diluted in the Y matrix. This identical power law strongly suggests that the exponent of the Raman relaxation process in the series of solid-state diluted isostructural compounds is practically independent of the metal ion (as long as the molar mass changes are negligible) and highlights a possible strategy towards a reliable Raman relaxation determination.