Syntheses, structures and photophysical properties of heterotrinuclear Zn2Lnclusters (Ln = Nd, Eu, Tb, Er, Yb)

Abstract

Heterotrinuclear Zn₂Ln (Ln = Nd 2, Eu 3, Tb 4, Er 5, Yb 6) clusters [(Znq₂)₂](μ-CH₃COO){Ln(hfac)₂} (q = 8-hydroxylquinolinate, hfac = hexafluoroacetylacetonate) have been synthesized. The Zn₂Ln framework is ligated by two q ligands featuring μ-phenoxo and two q ligands featuring μ₃-phenoxo coordination modes, and one μ-CH₃COO⁻ anions. Since the short intramolecular separations of Zn⋯Ln (ca. 3.354–3.373 Å) allow energy transfer from Znq₂-based sensitizers to the Ln^III centres through two energy transfer pathways, the lanthanide luminescence is indeed “lighted up” by excitation of the Znq₂-based chromopores. Photophysical measurements revealed that these Zn₂Ln complexes exhibit the so-called “dual emission” originating from both Znq₂-based luminophores and lanthanide emitters. By virtue of the dual luminescence with complementary colours, the Znq₂-based cyan emission and Eu^III-centred red luminescence are combined to generate a white-light emission in the Zn₂Eu (3) complex.