NIR luminescence from sandwich-type ytterbium(III) complexes constructed from β-diketone and bis-salicylaldehyde derivatives

Two near-IR emissive sandwich-type ytterbium complexes [Zn(OAc)(μ-L1)Yb(DBM)2] (1) and [Zn(OAc)(μ-L2)Yb(DBM)2] (2) were designed and synthesized. The sandwich structures were confirmed by single crystal X-ray crystallographic analysis, where one Yb3+ ion was sandwiched between one L and two DBM ligands (L1and L2 represents the bis-salicylaldehyde derivatives; DBM = dibenzoylmethane). Photophysical measurements demonstrated the excellent NIR luminescence properties with quantum yields (QYs) reaching to 0.50% and 2.22% for complexes 1 and 2, respectively. Combining the structure and spectroscopy evidences, it was suggested that the sandwich structure and heavy atom effects contributed to suppress the nonradiative decay rate and improve the intersystem crossing efficiency from singlet to triplet state. The sandwich-type ytterbium(III) complexes [Zn(OAc)(μ-L1)Yb(DBM)2] constructed from β-diketone and bis-salicylaldehyde derivatives shows the excellent NIR luminescence properties with quantum yields (QYs) reaching to 2.22%. It was suggested that the sandwich structure and heavy atom effects contributed to suppress the nonradiative decay rate and improve the intersystem crossing efficiency from singlet to triplet state. [Display omitted] •Two NIR-emitting heterobinuclear Zn–Ln complexes were synthesized.•The luminescence quantum yields reaching 2.22% for Br substituted complex 1.•The complexes show a more effective energy transfer in view of synergistic interaction between two ligands.