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

Abstract

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.