Pyrazine-driven dinuclear assembly of dysprosium(iii) β-diketonate complex: a fluxidentate bridging approach toward functional near-white luminescent materials

Abstract

Three single component Dy(III) complexes featuring β-diketone ligand TTBD (4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione) were studied for their potential as white-light emitters. The complexes include a water-containing species (DyA) and two anhydrous species (DyM and DyD) incorporating the auxiliary bidentate ligand pyrazine (pyz). The coordination geometry and ligand environment, particularly the nuclearity and presence of sensitizing co-ligands, significantly influence the relative intensities of the characteristic Dy(III) yellow ⁴F_9/2 → ⁶H_13/2 and blue ⁴F_9/2 → ⁶H_15/2 and ligand-based phosphorescence emissions. The introduction of pyrazine enhances energy transfer efficiency, leading to improved Dy(III) emission output. Chromaticity coordinates measured at RT indicate that DyA (0.339, 0.336), DyM (0.404, 0.428) and DyD (0.323, 0.367) emit light close to the ideal white light coordinates (0.333, 0.333) as defined by the CIE system. Corresponding CCT values further classify DyA (5202 K) and DyD (5845 K) as cool white emitters, while DyM (3786 K) lies within the neutral-yellowish range. Emission branching ratio (β_R) analysis reveals that the ⁴F_9/2 → ⁶H_13/2 transition dominates (>90%), suggesting its suitability for laser amplification applications. In addition to their visible-light emission, the Dy(III) complexes exhibit good thermal stability and semiconducting characteristics, as confirmed by thermogravimetric (TG) and UV-Vis studies, respectively. Collectively, these findings support the potential application of these Dy(III) complexes as efficient, single component emitters for white light emitting devices (WLEDs).