Diphospine-dioxide-containing Yb(III) and Er(III) molecular magnets in luminescent dicyanidometallate(I)- and Eu(III)-based frameworks

Lanthanide–based single–molecule magnets (SMMs) that combine both magnetic and optical properties are currently being developed for their potential applications in light and magnetic field sensing, as well as self-monitoring of temperature using optical thermometry in SMM-based devices. Herein, we report a family of novel molecule-based materials, based on the cyanido-bridged coordination polymers formed by 4f metal complexes bearing dppmO2 (bis(diphenylphosphino)methane dioxide) ligands, which are further linked by dicyanoargentate(I) ions, [AgI(CN)2]–, into unique heterometallic d–f cyanido–bridged chains of the formula {[LnIII(dppmO2)3][AgI(CN)2][OTf]2} (LnIII = Eu, Er, Yb}. They reveal the effects of slow relaxation of the magnetization below 10 K for Er(III)- and Yb(III)-based analogues (ErAg, YbAg), and strong red luminescence in the solid state for the Eu(III)–based derivative (EuAg). Therefore, by diluting the Er(III) or Yb(III) centers in the Eu(III)-based coordination matrix (Er@EuAg, Yb@EuAg), the presented system provides a stable platform for combining magnetic and photoluminescent properties. Based on the obtained experimental data with support of ab initio calculations, we discuss their magnetic properties and the influence of the Eu(III)–based matrix on the SMM behaviour of Er@EuAg and Yb@EuAg. In addition, we explore the photoluminescent properties of EuAg, Er@EuAg, and Yb@EuAg, and their potential use as optical thermometers, employing the excitation spectra of Eu(III).