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Seven coordination polymers having the general formula {[Ln2(2,6-pydc)(ox)2⋅(H2O)4]⋅3H2O}n (Ln = Sm 1, Eu 2, Gd 3, Tb 4, Dy 5, Ho 6, Er 7; 2,6-pydc2− = 2,6-pyridinedicarboxylate, ox2− = oxalate) were synthesized by the hydrothermal method. Their IR, UV-Vis-NIR absorption spectra, and Vis-NIR emission spectra were investigated, and the luminescent properties of the polymers were studied in detail. Crystal structures were determined by means of a single-crystal X-ray diffractometer, and all of them proved to have three-dimensional frameworks. Except for polymers 3 and 7, the polymers displayed the characteristic emissions of Ln(III) ions due to the effective sensitization of ligands. At the same time, the 4f orbitals of Ln(III) ions were shifted by the effects of ligand field, which influenced emission spectra and absorption spectra of some of the polymers.

A series of coordination polymers, {[LnZn(2,3-pydc)(1,3-bdc)(OH)(H2O)m]·H2O}n, (Ln = Sm 1, Eu 2, Gd 3, Tb 4, Dy 5, Er 6, Yb 7, Pr 8, Nd 9), (1–7, m = 1; 8, 9, m = 2), (2,3-H2pydc = pyridine-2,3-dicarboxylic acid, 1,3-H2bdc = isophthalic acid), are synthesized by the hydrothermal method and their crystal structures are determined by single-crystal X-ray diffraction. Structural analysis shows that coordination polymers 1–9 present two-dimensional layered structures and all of them are crystalized in triclinic system with space group Pī. Hereinto polymers 1–7 are isomorphous, while polymers 8 and 9 are also isomorphous and each of them includes one more coordinated water molecule than others. All coordination polymers are characterized by IR, UV–Vis–NIR and fluorescent spectra, and the luminescent properties are the research emphasis. In addition, except for polymer 3, the other eight Zn-Ln polymers exhibit the characteristic luminescence of corresponding Ln(III) ions, which should be owing to the sensitization of the Zn-Ligand moiety. With the influence of the crystal field and the introduction of Zn(II) ion, the internal energy levels of the system are tuned, which is reflected by shift and split of the partial characteristic bands of Ln(III) ions in their UV–Vis–NIR absorption spectra and NIR emission spectra, and both can corroborate each other.

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.

Eight novel coordination polymers, {[LnZn(2,3-pydc) 2 (ox) 0.5 (H 2 O) 3 ]·3H 2 O} n (Ln = Pr 1 , Nd 2 , Ho 3 , Er 4 , Yb 5 , Sm 6 , Eu 7 , Tb 8 ) (2,3-H 2 pydc = pyridine-2,3-dicarboxylic acid, H 2 ox = oxalic acid) are synthesized by the hydrothermal method and their structures are determined by single-crystal X-ray diffraction. They are isomorphous and crystallized in the triclinic system, with space group P 1 ¯ . In crystals, Ln(III) and Zn(II) ions are linked into 2D layers by 2,3-pydc 2− ligands adopting two coordination modes, and neighboring layers are bridged into 3D network structure through oxalate ligands in bridging tetradentate coordination mode. The IR, UV–Vis–NIR absorption spectra and emission spectra in the visible and near-infrared (NIR) region of polymers are determined and analyzed. All of polymers exhibit characteristic emission bands of corresponding Ln(III) ions, which should be attributed to sensitization from the d-block (Zn–ligand moiety) and ligands after introducing Zn(II) ion into the system of Ln(III) complexes.

Four Ln(III) coordination polymers, {[Ln2(1,3-bdc)3(H2O)4]·DMF·H2O}n (Ln = Sm 1, Eu 2) and [Ln2(mal)3(H2O)6]n (Ln = Sm 3, Eu 4) (1,3-H2bdc = isophthalate acid, H2mal = malonate acid), were hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, UV–Vis–NIR absorption spectra, and fluorescence spectra. The structural analyses reveal that polymer 1 is a 3D coordination polymer. Its asymmetry unit contains two crystallographically independent Sm(III) ions, both are eight-coordinated. The 1,3-bdc2− anions show three different coordination modes. The structure of polymer 2 is isomorphous with that of 1. Polymer 3 is also a 3D coordination polymer, its asymmetry unit contains one Sm(III) ion, which is nine-coordinate. The mal2− anions have two different coordination modes. The structure of polymer 4 is isomorphous with that of 3. The luminescent study shows that polymers 1, 2, and 4 exhibit characteristic emission bands in the visible region, corresponding to the transitions of the Ln(III) ions. By comparison and analysis of luminescence, it is found that the incidence of the same ligand on the corresponding spectra of different Ln(III) ions is different, and the influence of different ligands on luminescence of the same Ln(III) ion is also very different.

Four new lanthanide(Ш) coordination polymers, [Ln(p-aminobenzoate)2(DMF)(HCOO) (H2O)]n (Ln = Sm 1, Tb 2, Pr 3) and {[Pr(2,5-dcp)(CH3COO)(H2O)]·1.5H2O}n (4) (DMF = N,N-dimethylformamide, 2,5-dcp = pyridine-2,5-dicarboxylate), have been synthesized by hydrothermal method. The structures are determined by the single-crystal X-ray diffraction. The four polymers all crystallize in the monoclinic space group P21/n. Polymers 1 and 2 are isostructural; both SmIII ion of polymer 1 and TbIII ion of polymer 2 are eight-coordinate. Although polymer 3 possesses the same asymmetric unit as polymers 1 and 2, the three are not isomorphous. The PrIII ions in polymers 3 and 4 are nine-coordinate. In polymers 1, 2 and 3 the neighboring units are bridged by formyloxy and extend into infinite chains, which are connected by hydrogen bonds to form a hydrogen bond network. However, polymer 4 is bridged by pyridine-2,5-dicarboxylate and acetates to form an infinite 3D network. At room temperature, the IR, UV–Vis–NIR and emission spectra of the four polymers were measured and analyzed. The four polymers emit in the visible or NIR region. The luminescent properties are discussed.

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.

Three cadmium(II) coordination polymers [Cd(NA)2(H2O)2]n (1), {[Cd(NA)(phen)(NO3)]·(H2O)1/2}n (2), {[Cd(NA)(CH3C6H4COO)(H2O)2]·(CH3C6H4COOH)}n (3) (HNA = nicotinic acid, phen = 1, 10-phenanthroline) have been synthesized by hydrothermal method. Their single-crystal structures were determined by X-ray diffractometry. The absorption, excitation and emission spectra were investigated and all the complexes emit strong fluorescence: λemmax = 544 nm (λex = 492 nm), 1; λemmax = 466 nm (λex = 393 nm), 2; λemmax = 430 nm (λex = 313 nm), 3. At room temperature in the solid state the fluorescence lifetimes of the complexes were investigated and the relationships between the spectra were discussed as well as the connections of luminescence and crystal structures.