Zhong-Ming Sun

A layer-structured Eu-MOF as a highly selective fluorescent probe for Fe3+ detection through a cation-exchange approach

A new series of lanthanide metal–organic frameworks, LnL (Ln = La, Y, Eu, Tb, and Gd), were prepared under hydrothermal conditions. The five compounds are all isostructural as confirmed by the analyses of single crystal and powder X-ray diffractions. The compounds exhibit layer-like structures with the [H2NMe2]+ cations being located in the interlayer channels, which can be easily replaced by a number of metal ions. Most interestingly, compound EuL performs as a rare example of a highly selective and sensitive luminescence sensor for Fe3+ ions based on total quenching of the Eu-luminescence via cation-exchange. The possible sensing mechanism was further explored in detail. Remarkably, it is the first Eu-MOF luminescent material to exhibit an excellent ability for the detection of Fe3+ ions in a biological system.

Solvents control over the degree of interpenetration in metal-organic frameworks and their high sensitivities for detecting nitrobenzene at ppm level

Solvothermal syntheses in DMF and acetonitrile afforded two novel MOFs, Zn3(L1)2(L2)·3.6 DMF·4.0 H2O (1) and Zn3(L1)2(L2) (2) [L1 = 4-[3-(4-carboxyphenoxy)-2-[(4-carboxyphenoxy)methyl]-2-methyl-propoxy]benzoate, L2 = 1,4-bis(1-imidazolyl)benzene], respectively. Single crystal X-ray analyses reveal that 1 and 2 are structurally closely related with the same building blocks and 3-dimesional 3, 8-connected tfz-d net. 1 is based on a 2-fold interpenetrating network with extra-framework DMF and water molecules located in the void space, while 2 is different in its 3-fold interpenetrating network and absence of any solvent molecules. This simple and easy strategy unprecedentedly controls the degree of interpenetration in MOFs through varying solvents. Luminescent properties of activated phase 1′ and 2 well dispersed in different solvents have also been investigated systematically, which demonstrate distinct solvent-dependent luminescent spectra with emission intensities significantly quenched toward nitrobenzene (NB). For luminescence responses of 1′ and 2 dispersed in DMF solution with gradually increased NB contents, detectable quenching effects were observed even at a very low NB concentration of 50 ppm, indicating extremely high sensitivities of 1′ and 2 towards NB.

A Highly Anisotropic Cobalt(II)-Based Single-Chain Magnet: Exploration of Spin Canting in an Antiferromagnetic Array

In this article we report for the first time experimental details concerning the synthesis and full characterization (including the single-crystal X-ray structure) of the spin-canted zigzag-chain compound [Co(H2L)(H2O)]infinity [L = 4-Me-C6H4-CH2N(CPO3H2)2], which contains antiferromagnetically coupled, highly magnetically anisotropic Co(II) ions with unquenched orbital angular momenta, and we also propose a new model to explain the single-chain magnet behavior of this compound. The model takes into account (1) the tetragonal crystal field and the spin-orbit interaction acting on each Co(II) ion, (2) the antiferromagnetic Heisenberg exchange between neighboring Co(II) ions, and (3) the tilting of the tetragonal axes of the neighboring Co units in the zigzag structure. We show that the tilting of the anisotropy axes gives rise to spin canting and consequently to a nonvanishing magnetization for the compound. In the case of a strong tetragonal field that stabilizes the orbital doublet of Co(II), the effective pseudo-spin-1/2 Hamiltonian describing the interaction between the Co ions in their ground Kramers doublet states is shown to be of the Ising type. An analytical expression for the static magnetic susceptibility of the infinite spin-canted chain is obtained. The model provides an excellent fit to the experimental data on both the static and dynamic magnetic properties of the chain.

Tunable emission based on lanthanide(III) metal-organic frameworks: an alternative approach to white light

A new family of lanthanide metal–organic frameworks, LnL (Ln = Y, La–Yb, except Pm), were synthesized under hydrothermal conditions based on a semi-rigid trivalent carboxylic acid. All LnMOFs are isostructural based upon the analyses of single crystal and powder X-ray diffractions. The optical properties of compounds LnL can be easily tuned by doping methods, allowing for the syntheses of the materials with enhanced visible emission properties. Considering the intense blue-emission of the Dy compounds, it is expected that white light can be achieved by doping Dy and other red-emission lanthanide ions, such as Eu3+ or Sm3+. For the first time, without involving any emission from organic ligands, white-light emission was successfully realized by codoping Dy/Eu or Dy/Sm into analogic Gd compounds.

Tertiary Carbinamine Synthesis by Rhodium-Catalyzed [3 + 2] Annulation of N-Unsubstituted Aromatic Ketimines and Alkynes

A convenient and waste-free synthesis of indene-based tertiary carbinamines by rhodium-catalyzed imine/alkyne [3+2] annulation is described. Under the optimized conditions of 0.5-2.5 mol % [{(cod)Rh(OH)}(2)] (cod=1,5-cyclooctadiene) catalyst, 1,3-bis(diphenylphosphanyl)propane (DPPP) ligand, in toluene at 120 degrees C, N-unsubstituted aromatic ketimines and internal alkynes were coupled in a 1:1 ratio to form tertiary 1H-inden-1-amines in good yields and with high selectivities over isoquinoline products. A plausible catalytic cycle involves sequential imine-directed aromatic C-H bond activation, alkyne insertion, and a rare example of intramolecular ketimine insertion into a Rh(I)-alkenyl linkage.

MOF-76: from a luminescent probe to highly efficient U(VI) sorption material.

MOF-76 exhibits not only high sensitivity for the detection of U(vi), but also high adsorption capacity of 298 mg g(-1) at a low pH value of ∼3.0. Furthermore, the high selectivity for uranium adsorption over a series of competing metal ions is also illustrated.

Highly selective acetone fluorescent sensors based on microporous Cd(II) metal–organic frameworks

Solvothermal reaction of Cd2+ ions and a hexavalent carboxylic acid (H6666666L) afforded a Cd(II) metal organic framework (Cd-MOF), namely {[Cd3(L)(H2O)2(DMF)2]·5DMF}n (1). Its structure consists of trinuclear CdII building units, which are further bridged by the carboxylic ligand, resulting in a 4,4-connected topological net (sra). By introducing a rigid N-donor ligand 1,4-bis(1-imidazolyl)benzene (dib), a new Cd-MOF (2) {[Cd3(L)(dib)]·3H2O·5DMA}n was isolated, in which the coordinated sites of solvent molecules in 1 were completely replaced by dib. The resulting trinuclear Cd3 subunits are further bridged into a two-fold interpenetrating network with DMA and water molecules located in the void space. The luminescent properties of the two microporous Cd-MOFs dispersed in different solvents have been investigated systematically, demonstrating unique selectivity for the detection of acetone via a fluorescence quenching mechanism. Their luminescence intensities decreased to 50% at an acetone content of 0.3 vol% and were almost completely quenched at a concentration of 1.0 vol%, thus, they can be considered as excellent potential luminescent probes for the detection of acetone.

Rh(I)-catalyzed decarboxylative transformations of arenecarboxylic acids: ligand- and reagent-controlled selectivity toward hydrodecarboxylation or Heck-Mizoroki products.

A Rh(I)-based catalyst system has been developed to promote three types of decarboxylative transformations of arenecarboxylic acids: (1) hydrodecarboxylation, (2) Heck-Mizoroki olefination, and (3) conjugate addition. Scopes of reactions (1) and (2) were studied, and the ligand and reagent dependence of selectivity was explored.

Rh(I)-Catalyzed Olefin Hydroarylation with Electron-Deficient Perfluoroarenes

Assisted by a partially aqueous media, a catalyst system of [Rh(cod)(OH)](2) and DPPBenzene ligand effectively promotes direct conjugate additions by perfluoroarenes. This formal C-H alkylation process represents a rare example of olefin hydroarylation with electron-deficient arenes. The catalyst system can be modified to selectively form the corresponding olefination products under anhydrous conditions.

3-Fold-Interpenetrated Uranium–Organic Frameworks: New Strategy for Rationally Constructing Three-Dimensional Uranyl Organic Materials

The first series of 3-fold-interpenetrated uranium-organic frameworks, UOF-1 and UOF-2, have been synthesized by hydrothermal reactions of flexible semirigid carboxylic acids and uranyl nitrate. Structure analyses indicate that UOF-1 and UOF-2 possess flu and pts topologies, respectively.