Design of DyIII single-molecule magnets with molecularly installed luminescent thermometers based on bridging [PtII(CN)2(C^N)]− complexes†

Luminescent Single-Molecule Magnets (SMMs) have gained broad scientific attention due to their potential applications in the dual sensing of temperature and magnetic field or optical thermometry for the self-monitoring of temperature in SMM-based devices. We present a route toward thermoresponsive emissive SMMs based on linking two molecular components separately providing luminescent thermometry and SMM features. We combined Dy(III) centers of a rationally constrained coordination sphere giving tunable magnetic anisotropy with an emissive dicyanido(2-phenylpyridinato)platinate(II) anion, [Pt^II(CN)₂(ppy)]⁻ exhibiting ratiometric optical thermometry. These molecular precursors undergo self-assembly into {[Dy^III(MeOH)₂(NO₃)]₂[Pt^II(CN)₂(ppy)]₄}·n(solvent) (1) coordination chains of a weak field-induced SMM behavior. However, upon the exchange of MeOH molecules, axially aligned within eight-coordinated Dy(III) complexes, by O-donor organic ligands, including 4(1H)-pyridone (2), pyridazin-4(1H)-one (3), and N-methyl-pyridin-4(1H)-one (4), an improvement of the SMM character was achieved. This is accompanied by the tuning of optical thermometry related to temperature-variable excitation and emission spectra of Pt(II) complexes which leads to the best-performance multifunctionality in a 4(1H)-pyridone-containing compound. Our work proves that the heterometallic synthetic approach provides a unique class of SMM-based luminescent thermometers where lanthanide-centered magnetism will not be affected by the light employed to monitor the temperature through an optical process occurring in attached cyanido transition metal complexes.