A Luminescent Thermometer Exhibiting Slow Relaxation of the Magnetization: Toward Self-Monitored Building Blocks for Next-Generation Optomagnetic Devices

TLDR

Single‑molecule magnets are promising for molecular electronics, but heat generated by electric currents poses a significant challenge during device fabrication. The study aims to develop multifunctional single‑molecule magnets that can accurately measure temperature at sub‑micrometer scales. Using 2,2′‑bipyrimidine and 1,1,1‑trifluoroacetylacetonate ligands, the authors synthesized a dinuclear Dy₂ complex that exhibits slow magnetic relaxation and strong photoluminescence. The resulting Dy₂ complex functions as a self‑calibrated luminescent thermometer, enabling temperature sensing from 5 to 398 K via two distinct thermal‑dependent spectral shifts, while retaining its single‑molecule magnet behavior and revealing optomagnetic cross‑effects.

Abstract

The development and integration of Single-Molecule Magnets (SMMs) into molecular electronic devices continue to be an exciting challenge. In such potential devices, heat generation due to the electric current is a critical issue that has to be considered upon device fabrication. To read out accurately the temperature at the submicrometer spatial range, new multifunctional SMMs need to be developed. Herein, we present the first self-calibrated molecular thermometer with SMM properties, which provides an elegant avenue to address these issues. The employment of 2,2'-bipyrimidine and 1,1,1-trifluoroacetylacetonate ligands results in a dinuclear compound, [Dy2(bpm)(tfaa)6], which exhibits slow relaxation of the magnetization along with remarkable photoluminescent properties. This combination allows the gaining of fundamental insight in the electronic properties of the compound and investigation of optomagnetic cross-effects (Zeeman effect). Importantly, spectral variations stemming from two distinct thermal-dependent mechanisms taking place at the molecular level are used to perform luminescence thermometry over the 5-398 K temperature range. Overall, these properties make the proposed system a unique molecular luminescent thermometer bearing SMM properties, which preserves its temperature self-monitoring capability even under applied magnetic fields.