Ancillary ligand modulation in fluorinated β-diketonate Dy(iii) complexes: spectroscopic and photophysical investigations.

A series of semiconducting and luminescent dysprosium(iii) complexes (DB1-DB4) were synthesized using 4,4,4-trifluoro-1-phenyl-1,3-butanedione as a fluorinated β-diketone sensitizer along with bidentate ancillary ligands (BPy, B1, B2 and B3). FT-IR and 1H NMR spectroscopic analyses support effective ligand coordination and the formation of the proposed Dy(iii) complexes. Thermogravimetric analysis reveals good thermal stability with high decomposition temperatures, demonstrating suitability for device processing and operational durability. Optical and electrochemical investigations were performed to establish structure-property correlations. The HOMO-LUMO energy gaps of DB1-DB4 were found in the range of 2.88-3.14 eV, consistent with electrochemical data and indicative of wide-band-gap semiconducting behavior. Photoluminescence studies exhibit a dominant emission band around 575 nm, assigned to the characteristic 4F9/2 → 6H13/2 transition of Dy(iii), producing intense yellow emission. The combined contribution of ligand-centered blue emission and Dy(iii)-centered yellow emission results in near-white light output, as confirmed by CIE chromaticity coordinates. The integration of semiconducting electronic structure, efficient ligand to metal energy transfer, near-white emission and robust thermal stability highlights the potential of these Dy(iii) complexes as promising materials for optoelectronic applications, particularly in white light-emitting diodes and display technologies.