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Abstract: Six novel heterometallic Zn–Ln coordination polymers {[ZnLnCl(pydc)2(H2O)6]·3H2O} n (Ln=Nd 1, Pr 2, Sm 3, Eu 4, Tb 5, Dy 6; pydc=pyridine-2,5-dicarboxylate) were synthesized by the hydrothermal method, and their structures were measured by the single-crystal X-ray diffraction. The IR and UV–Vis–NIR absorption spectra, and the luminescence spectra in the visible and near-infrared (NIR) regions of the six complexes were determined at room temperature. They possess the same crystal structure, and the Zn(II) and Ln(III) ions in each complex are bridged into 1D infinite chain by pyridine-2,5-dicarboxylates. Meanwhile, there are numerous hydrogen bonds which result in the 3D hydrogen bonding network in the crystal. In the visible and NIR regions, the emission spectra of the complexes show the characteristic bands of the corresponding Ln(III) ions, which are mainly attributed to the sensitization from the d-L-moiety to f-L-moiety after forming the Zn–Ln complexes. In this paper, we first report the Zn–Sm complex which can exhibit the emission bands of Sm(III) in the NIR region, and discuss the sensitization from the d-L-moiety to f-L-moiety on the basis of the different characteristics of levels for different Ln(III) ions. [Copyright &y& Elsevier]

Six Zn-Ln coordination complexes, [Nd 2 Zn 2 (C 6 H 5 COO) 10 (Imh) 2 (H 2 O) 2 ] ( 1 ), [Pr 2 Zn 2 (C 6 H 5 COO) 10 (Imh) 2 (H 2 O) 2 ] ( 2 ), [ErZn 2 (C 6 H 5 COO) 7 (Imh) 2 ] ( 3) , [HoZn 2 (C 6 H 5 COO) 7 (Imh) 2 ] ( 4 ), [EuZn 2 (C 6 H 5 COO) 7 (Imh) 2 ] ( 5 ), [TbZn 2 (C 6 H 5 COO) 7 (Imh) 2 ] ( 6 ) (C 6 H 5 COOH=benzoic acid, Imh=imidazole) have been synthesized under hydrothermal conditions and their crystal structures have been characterized by single crystal X-ray diffraction. All complexes are crystallized in triclinic system, with space group P ī. Complexes 1 and 2 are isomorphous with tetranuclear molecular structure and complexes 3–6 are isomorphous and trinuclear molecular complexes. All complexes are characterized by IR, UV–Vis–NIR and luminescent spectra in the visible and near-infrared (NIR) regions at room temperature. The study of luminescent properties indicates that all complexes exhibit the characteristic emission bands of corresponding Ln(III) ions, which should be attributed to sensitization from d-block and ligands after introducing Zn(II) ion and ligands into the system of Ln(III) complexes. Moreover, the NIR emission bands of complexes 1–4 exhibit shift and split, which can be evidenced in their UV–Vis–NIR absorption spectra. [ABSTRACT FROM AUTHOR]