Seven new isostructural lanthanide metal-organic frameworks (Ln-MOFs), [Ln(Hpzbc)2(NO3)]·H2O (1-Ln, Ln = Nd(3+), Sm(3+), Eu(3+), Gd(3+), Tb(3+), Er(3+), and Yb(3+) ions, H2pzbc = 3-(1H-pyrazol-3-yl) benzoic acid), with one-dimensional (1D) channels decorated by nitrate anions and pyrazoyl groups have been constructed. 1-Ln, as revealed by structural analysis, represent uncommon microporous 3D Ln-pyrazoyl-carboxyl systems using pyrazoyl-carboxyl bifunctional ligands as bridges. The luminescent investigations show that 1-Eu is an excellent MOF-based fluorescent probe, with high sensitivity, selectivity, and simple regeneration, for environmentally relevant Fe(3+) and Cr2O7(2-) ions. 1-Eu also presents highly selective capture for CO2 over N2 and CH4 due to the multiple binding sites for CO2 molecules, which were supported by Grand Canonical Monte Carlo (GCMC) simulations.

Uncommon pyrazoyl-carboxyl bifunctional ligand-based microporous lanthanide systems: sorption and luminescent sensing properties

A new zinc compound, together with a corresponding series of Zn-4f heterometallic coordination polymers, namely, [Zn(H2PBDA)(PBDA)]n (1), {[Ln2(PBDA)2·2H2O] [Zn2(PBDA)2Cl2]}n [H2PBDA = 3-(pyridin-3-yl-oxy) benzene-1,2-dicarboxylic acid, and Ln = Pr(2), Nd(3), Eu(4), Gd(5), Dy(6), Ho(7), Er(8)] have been hydrothermally synthesized and characterized systematically. Polymers 2–8 feature two-dimensional (2D) 4,4 networks, containing the original 1D heterometallic double stranded chains composed of [Ln2Zn2(PBDA)2] entities. The extensive hydrogen bonding and π–π stacking interactions were observed to stabilize the extended architectures. The luminescence emission spectra of the polymers vary depending on the lanthanide(III) ion present. Informative magnetic susceptibility measurements show that the same carboxylate bridging fashion of the PBDA ligand results in the different magnetic properties occurring within the heterometallic coordination polymers. In addition, polymer 6 exhibits an interesting slow magnetic relaxation behavior at lower temperatures.

A series of Zn-4f heterometallic coordination polymers and a zinc complex containing a flexible mixed donor dicarboxylate ligand.

Polycyanometallate compounds with both photochromism and photomagnetism have appealing applications in optical switches and memories, but such optical behaviors were essentially restricted to the cryogenic temperature. We realized, for the first time, the photochromism and photomagnetism of 3d-4f hexacyanoferrates at room temperature (RT) in [Eu(III)(18C6)(H2O)3]Fe(III)(CN)6·2H2O (18C6 = 18-crown-6). Photoinduced electron transfer (PET) from crown to Fe(III) yields long-lived charge-separated species at RT in air in the solid state and also weakens the magnetic susceptibility significantly. The PET mechanism and changing trend of photomagnetism differ significantly from those reported for known 3d-4f hexacyanoferrates. This work not only develops a new type of inorganic-organic hybrid photochromic material but opens a new avenue for RT photomagnetic polycyanometallate compounds.

Photochromism and Photomagnetism of a 3d-4f Hexacyanoferrate at Room Temperature.

Six novel three-dimensional (3D) lanthanide metal–organic frameworks (LnMOFs), {[Ln2(ispc)3(H2O)3]·mH2O}n (Ln = Pr (1, m = 5); Eu (2, m = 5); Gd (3, m = 4); Tb (4, m = 5); Dy (5, m = 5) and Ho (6, m = 4)), ispc = 3-(4-carboxyphenylsulfonyloxy)-4-methoxybenzoic anion) have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction revealed they are isostructural and crystallize in the triclinic crystal system, space group P. The investigations on luminescent properties and lifetimes of 2 (EuIII), 4 (TbIII), and 5 (DyIII) exhibit characteristic emissions of EuIII, TbIII and DyIII ions and the corresponding luminescent lifetimes are 0.14 ms, 9.93 μs and 1.25 ms, respectively. The different luminescent intensities and lifetimes among them were further discussed. Furthermore, magnetic studies of 1–6 reveal that 3–6 exhibit ferromagnetic coupling, and 5 (DyIII) exhibits remarkably slow magnetic relaxation behavior with the energy barrier ΔE/kB = 49.2 K.

Structures, luminescent and magnetic properties of six lanthanide-organic frameworks: observation of slow magnetic relaxation behavior in the DyIII compound.

Five isostructural three-dimensional (3D) lanthanide (Ln) frameworks [LnCl(bpdc)(DMF)] (Ln = La (1), Ce (2), Pr (3), Nd (4), and Sm (5), H2bpdc = 4,4′-biphenyl-dicarboxylic acid, DMF = N,N-dimethylformamide) have been solvothermally synthesized and characterized by TGA, IR, and X-ray single crystal diffraction. The frameworks contain unusual Ln-carboxylate/Cl chains, and which are extended by bpdc2- linkers to form 4-connected sra networks with 1D rhombic channels. The effect of lanthanide contraction induces the decreases of average Ln–O and Ln–Cl distances from La to Sm. 4 exhibits strong characteristic luminescence of Nd3+ ions in the near-infrared (NIR) region, resulting from the sensitization of bpdc2–. 3 displays weak NIR emission due to the inefficient sensitization of Pr3+ ions. The depopulation of the Stark levels and possible antiferromagnetic interactions within the Ln-carboxylate/Cl chains lead to the continuous decreases of χMT for 2–4 along the decreasing temperatures.

Five sra Topological Ln(III)-MOFs Based on Novel Metal-Carboxylate/Cl Chain: Structure, Near-Infrared Luminescence and Magnetic Properties

A series of novel one-dimensional (1-D) lanthanide coordination polymers (CPs), with the general formula {[Ln(bptcH)(H2O)2]·H2O}n (Ln = NdIII (1), EuIII (2), GdIII (3), TbIII (4), DyIII (5), HoIII (6), or ErIII (7)) have been synthesized by the solvothermal reactions of the corresponding lanthanide(III) picrates and 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid (bptcH4). These polymers have been structurally characterized by single-crystal X-ray diffraction, IR, PXRD, thermogravimetric (TGA), and elemental analysis. Coordination polymers 1–7 are isostructural; they possess the same 3D supramolecular architectures and crystallize in triclinic space group P1. The frameworks constructed from dinuclear lanthanide building blocks exhibit one-dimensional double-stranded looplike chain architectures, in which the bptcH3– ions adopted hexadentate coordination modes. The EuIII (2) and TbIII (4) polymers exhibit characteristic photoluminescence in the visible region. The magnetic properties of polymers 2, 3, and ...

Syntheses, Structures, Luminescence, and Magnetic Properties of One-dimensional Lanthanide Coordination Polymers with a Rigid 2,2′-Bipyridine-3,3′,6,6′-tetracarboxylic Acid Ligand

Six new organic salts containing flexible and polydentate bis(2-benzimidazylmethyl)amine (BBMA) and a variety of carboxylic acids, including benzoic acid (HBA), p-nitrobenzoic acid (4-NHBA), 3,5-di...

Network Formation of Bis(2-benzimidazylmethyl)amine in Salts with Carboxylic Acids: The Structures Based on the Interplay of Strong and Weak Intermolecular Interactions

Peng Liu

Papers

Syntheses, Structures, Luminescence, and Magnetic Properties of One-dimensional Lanthanide Coordination Polymers with a Rigid 2,2′-Bipyridine-3,3′,6,6′-tetracarboxylic Acid Ligand

Network Formation of Bis(2-benzimidazylmethyl)amine in Salts with Carboxylic Acids: The Structures Based on the Interplay of Strong and Weak Intermolecular Interactions