Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry

International audienceThis article is part of the thematic issue "Advanced hybrid nanomaterials". Associate Editor: S. A. Claridge © 2018 Farger et al.; licensee Beilstein-Institut. License and terms: see end of document. Abstract The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H 2 O)] with Ln = Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ and Yb 3+ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO 3) 3 ·xH 2 O with the 1,3-bis(carboxymethyl)imidazolium [HL] ligand and oxalic acid (H 2 ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostruc-tural networks of formula [Tb 1−x Eu x (L)(ox)(H 2 O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as lumines-cent ratiometric thermometers based on the emission intensities of ligand, Tb 3+ and Eu 3+. The best sensitivities were obtained using the ratio between the emission intensities of Eu 3+ (5 D 0 → 7 F 2 transition) and of the ligand as the thermometric parameter. [Tb 0.97 Eu 0.03 (L)(ox)(H 2 O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%·K −1 at 340 K. 277