Sunlight-Driven Emission of Eu ³⁺ and Tb ³⁺ Nalidixate Complexes: Achieving Visible Red and Green Light in PMMA Films

High Resolution Image Download MS PowerPoint Slide In this work, a series of complexes with the general formula [RE 2 (nal) 6 (H 2 O) 3 ]·9H 2 O (RE 3+: Eu, Gd, and Tb) was successfully synthesized. The crystal structure of the Tb 3+ compound was determined by single-crystal X-ray diffraction, revealing a bimetallic arrangement with distinct coordination environments. Photophysical properties indicate that the Tb 3+ complex shows efficient sensitization through the S 1 level of the nal ligand. The presence of an LMCT band in the Eu 3+ complex does not result in significant luminescence quenching. This can be attributed to hydrogen-bonding interactions within its structure and to the nal ligand’s high capacity as an indirect luminescence sensitizer. As a result, the Eu 3+ complex exhibits a relatively high intrinsic quantum yield value (∼24%) for a highly hydrated system. The PMMA:(1%)Eu 3+ film shows a higher yield of highly luminescent films (54%) than the complex. In addition, the PMMA doped with Eu 3+ and Tb 3+ ions exhibits red and green emission under solar exposure. To the best of our knowledge, this behavior has not yet been reported in the scientific literature, considering the same ligand. These findings highlight the potential of these photonic materials as candidates for luminescent solar concentrator (LSC) devices.