Magneto-optical response and luminescence properties of lanthanide-titanium-oxo clusters <bold/> and <bold/>

The study of magneto-optical effects based on the f-f emission and absorption of lanthanide ions has attracted considerable interest. In this work, we present a series of isostructural lanthanide-titanium-oxo clusters (LTOCs) Ln2Ti7 (Ln = La, Sm, Eu) using 3,5-di-tert-butylbenzoic acid as the ligand. A detailed comparison of the luminescence properties of Sm2Ti7 and Eu2Ti7 shows that Eu2Ti7 displays superior luminescence intensity, higher color purity red light, longer lifetime, and significantly higher quantum yield. These properties, along with its high stability in solution, make Eu2Ti7 an excellent candidate for magnetic circularly polarized luminescence (MCPL) studies. Under an external magnetic field, Eu2Ti7 exhibited strong MCPL signals, with the maximum |gMCPL| value being 0.04 T-1 from the 5D0 -> 7F4 transition. In contrast, the weaker luminescence of Sm2Ti7 rendered MCPL analysis ineffective; however, its strong near-infrared absorption allowed for magnetic circular dichroism (MCD) studies. The MCD spectra of Sm2Ti7 revealed significant signals corresponding to f-f transitions in the 900-1600 nm range, with the maximum |gMCD| value observed at 1102 nm. This work provides valuable insights into the magneto-optical properties of Ln-based clusters, emphasizing the role of energy-level analysis for further research into their potential applications in magneto-optical devices.