Heterobimetallic 3d–4f Zn(II)–Ln(III) (Ln = Sm, Eu, Tb and Dy) complexes with a N 2 O 4 bisoxime chelate ligand and a simple auxiliary ligand Py: Syntheses, structures and luminescence properties

Four new 3d–4f heterobinuclear complexes [Zn(L)Sm(Py)(NO3)3] (1), [Zn(L)Eu(OAc)(NO3)2] (2), [Zn(L)Tb(Py)(NO3)3] (3) and [Zn(L)Dy(OAc)(NO3)2] (4); Py = pyridine; H2L = 6,6′-dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) have been successfully prepared by the one-pot reaction of H2L with zinc(II) acetate, lanthanide(III) nitrate and a simple auxiliary ligand Py. Although the heterobinuclear complexes 1–4 are prepared in the same reaction condition, the auxiliary ligand Py doesn’t coordinate to the Zn(II) center of the complexes 2 and 4. Instead, the bridging µ-acetato ligand is present in the complexes 2 and 4. The coordination of the auxiliary ligand Py in the complexes 1 and 3 leads to the smaller distortion of square pyramidal coordination site of Zn(II), the higher coplanarity between the planes of ZnO(phenoxo)2 and LnO(phenoxo)2, and the longer Zn⋯Ln distance compared with the complexes 2 and 4. Moreover, the ligand (L)2− can selectively sensitize Sm(III) ion from among Sm(III), Eu(III), Tb(III) and Dy(III) ions, although these complexes would often exhibit f–f luminescence.