Synthesis and Properties of Highly Efficient Luminescent Zn-Tb and Zn-Eu Multimetal Complexes

Abstract

Salen-type Schiff-base ligands (H₂L) were synthesized through the condensation reaction between 1,2-diphenylethane-1,2-diamine and o-vanillin. Three novel luminescent Zn-Ln complexes, [ZnL]₂Ln (Ln = Gd, Tb, Eu), were successfully prepared by reacting the zinc complex (ZnL) with LnCl₃. Subsequent treatment of [ZnL]₂Ln with dibenzoylmethane yielded three dinuclear derivatives, β-[ZnL]Ln (Ln = Gd, Tb, Eu). All complexes were comprehensively characterized by single-crystal X-ray diffraction and FT-IR spectroscopy. Structural analyses revealed that complexes 1–3 adopt trinuclear Zn-Ln-Zn architectures, whereas complexes 4–6 exhibit dinuclear Zn-Ln configurations. Solid-state photoluminescence measurements demonstrated quantum yields of 27.94% (ZnL), 0.90% ([ZnL]₂Eu), 1.82% ([ZnL]₂Tb), 1.05% ([ZnL]₂Gd), 0.65% (β-[ZnL]Eu), 1.16% (β-[ZnL]Tb), and 0.70% (β-[ZnL]Gd), indicating their potential as advanced fluorescent rare-earth materials. The LED devices based on complexes β-[ZnL]Eu and β-[ZnL]Tb exhibit stronger emission intensities compared to those based on complexes [ZnL]₂Eu and [ZnL]₂Tb. The obtained complexes were fabricated in LED; the CIE chromaticity coordinates of complexes β-[ZnL]Eu and β-[ZnL]Tb are (0.344, 0.316) and (0.347, 0.323), respectively, which are very close to the standard white light coordinates (0.33, 0.33).