Desolvation-Induced Highly Symmetrical Terbium(III) Single-Molecule Magnet Exhibiting Luminescent Self-Monitoring of Temperature

A conjunction of Single-Molecule Magnet (SMM) behavior and luminescence thermometry is an emerging research line aiming at contactless read-out of temperature in future SMM-based devices. The shared working range between slow magnetic relaxation and the thermometric response is typically narrow or absent. We report Tb^III-based emissive SMMs formed in a cyanido-bridged framework whose properties are governed by the reversible structural transformation from Tb^III(H₂O)₂]Co^III(CN)₆] ? 2.7H₂O ( 1 ) to its dehydrated phase, Tb^IIICo^III(CN)₆] ( 2 ). The 8-coordinated complexes in 1 show the moderate SMM effect but it is enhanced for trigonal-prismatic Tb^III complexes in 2 , showing the SMM features up to 42 K. They are governed by the combination of QTM, Raman, and Orbach relaxation with the energy barrier of 594(18) cm^?1 (854(26) K), one of the highest among the Tb^III-based molecular nanomagnets. Both systems exhibit emission related to the f–f electronic transitions, with the temperature variations resulting in the optical thermometry below 100 K. The dehydration leads to a wide temperature overlap between the SMM behavior and thermometry, from 6 K to 42 K. These functionalities are further enriched after the magnetic dilution. The role of post-synthetic formation of high-symmetry Tb^III complexes in achieving the SMM effect and hot-bands-based optical thermometry is discussed.