A Dy3+ Single-Molecule Magnet as a Dual-Mode Luminescent and Magnetic Thermometer

Metal-ion-assisted Schiff-base condensation enabled the isolation of the complex [Dy(LN6prop)(CH3COO)2](BPh4) (1), which undergoes a ligand exchange reaction with triphenylsilanolate to yield [Dy(LN6prop)(CH3COO)(OSiPh3)](BPh4)·0.5CH2Cl2 (2·0.5CH2Cl2). The crystal structure of 2·0.5CH2Cl2 reveals that the Dy3+ ion is coordinated in an N6O3 environment, adopting a distorted capped square antiprism geometry. 2·0.5CH2Cl2 is a single ion magnet, exhibiting magnetic relaxation in the 2–22 K range with an energy barrier of 465 K, consistent with ab initio calculations and luminescent measurements. 2·0.5CH2Cl2 also functions as a luminescent thermometer with maximum sensitivity SrΔ of 1% K–1 at 12 K. In addition, 2·0.5CH2Cl2 also shows magneto-thermometry, based on magnetic relaxation time (τ) and inverse magnetic susceptibility (1/χ). This magneto-thermometer achieves relatively high magneto-thermal sensitivities (Smax) of 9.3 % K–1 (Sr1/χ) at 10 K and 20 % K–1 (Srτ) at 9 K, while both Sr parameters remain well above 1% K–1 across the entire single-molecule magnet (SMM) operating range. Overall, 2·0.5CH2Cl2 constitutes a bifunctional molecular material, integrating SMM behavior with efficient dual-mode luminescent and magnetic thermometry.