Solvato Modulation of the Magnetic Memory in Isotopically Enriched Erbium Polyoxometallate.

Abstract

Single-Molecule Magnet (SMM) property is molecular by essence while commonly measured in solid crystalline state. Solvent crystallization molecules are usually neglected in the analysis and interpretation of solid state properties. Solvation/desolvation process in the polyoxometallate(POM)-based Na 9 [Er(W 5 O 18 ) 2 ]·35H 2 O SMM demonstrates that the dehydrated form relaxes more than 1000 times faster than the initial state while the rehydration process allows the quasi complete recovering of the initial magnetic behaviour. This dehydration process is monitored by Thermogravimetric Analysis (TGA) and temperature dependent X-ray powder diffraction, and rationalized by periodic quantum chemical calculations evidencing the tremendous role of the labile water molecules in the stability of the edifice. Ab-initio calculations highlight that sodium ions localization in the structure drive the magnetic responses. Isotopic enrichment with nuclear spin free ( 166 Er, I=0) Er III ions shows that the relaxation dynamics in the quantum regime depends on the nuclear spin.