Professor Muralee Murugesu (University of Ottawa) Seminar

Title: Design and Synthesis of Organometallic Compounds for Magneto-Optical Thermometry Abstract: Luminescence thermometry offers remote, non-invasive temperature readout with high spatial resolution, and lanthanide ions are ideal probes. Unlike the sharp, environment-insensitive 4f–4f emission of LnIII ions, the Laporte-allowed 5d→4f emission of EuII is broad and strongly dependent on the ligand field, enabling band-shift thermometry. Here, a BH4-bridged Cp*EuII complex is the first discrete organometallic EuII band-shift thermometer, with an emission shift of 1899 cm−1 over 60–320 K and the highest absolute thermal sensitivity reported to date. A systematic study of analogues bearing different cyclopentadienyl ligands and coordinating solvents, combined with variable-temperature single-crystal X-ray diffraction, reveals that near-identical structures can give vastly different emission properties, with the Eu···Eu′ separation, the Eu–Cp plane distance, and metal–ligand rigidity governing performance. Building on this, we developed a new family of phosphine chalcogenide-functionalized cyclopentadienides, K[C5Me4(PCh(NMe2)2)] (Ch = S, Se, Te), which form homoleptic europocenes in which the pendant P=Ch arms also coordinate the metal. Magnetic circular dichroism (MCD) spectroscopy reveals these to be outstanding magneto-optical thermometers, reaching relative sensitivities up to 113.8 % K−1 at cryogenic temperatures, a regime inaccessible to conventional luminescence thermometry, with the applied field allowing sensitivity to be traded for range. The same ligand platform also affords the DyIII metallocenium [(CpPS)2Dy][BPh4], a single-molecule magnet with Ueff = 822 cm−1 and open hysteresis with a ~1 T coercive field at 1.9 K. Together, these results establish organometallic lanthanide complexes as versatile platforms for multifunctional magneto-optical materials. See more of Dr. Murugesu's research on his website: http://www.murugesugroup.com/