Chuanlei Zhang

Two Lanthanide Metal–Organic Frameworks as Remarkably Selective and Sensitive Bifunctional Luminescence Sensor for Metal Ions and Small Organic Molecules

Two lanthanide metal-organic frameworks (Ln-MOFs) with similar structures have been synthesized through objective synthesis. The two compounds are both 2-fold interpenetrating 3D frameworks. Topological analyses reveal that complexes 1 and 2 are 6-connected pcu net. In addition, both structures were embedded in uncoordinated nitrogen atoms. As the uncoordinated pyridine groups can be used as functional groups, we tested their sensing ability toward metal ions and small organic molecules. To our delight, fluorescence measurements show the two complexes can selectively and sensitively detect for Fe3+ ion and nitromethane, which suggests that the two Ln-MOFs are promising bifunctional luminescence sensor materials with sensing metal ions and small organic molecules.

Four new metal–organic frameworks based on a rigid linear ligand: synthesis, optical properties and structural investigation

Four coordination polymers, namely, {[Cd(L)(BIP)]·3H2O}n (1), {[Co(L)(BIBP)(H2O)4]·4H2O}n (2), {[Ni(L)(BIBP)(H2O)2]·2DMF}n (3), [Ni(L)(BIMB)(DMF)(H2O)]n (4), have been synthesized based on a rigid linear carboxylate ligand (H2L = 2′,5′-dimethoxy-[1,1′:4′,1′′-terphenyl]-4,4′′-dicarboxylic acid) and different lengths of imidazole ligands (BIP = 1,4-di(1H-imidazol-1-yl)benzene; BIBP = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl; BIMB = 4,4′-bis((1H-imidazol-1-yl)methyl)-1,1′-biphenyl). These complexes have been characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction measurements. Complex 1 is a 6-connected 3-fold interpenetrating pcu net with the point symbol {412·63}, 2 is a 1D supramolecular chain-like structure, 3 and 4 can be simplified as 4-connected sql nets with the point symbol {44·62}. In addition, UV-visible spectra and photoluminescent properties are also investigated in detail.

Syntheses, characterization, and properties of five coordination compounds based on the ligand tetrakis(4-pyridyloxymethylene)methane

A nonplanar tetrahedral pyridine ligand has been synthesized and applied to assemble five metal–organic frameworks (MOFs) with novel structural features under solvothermal conditions, namely, {[Cu2(TPOM)(adi)2](H2O)4}n (1), {[Zn2(TPOM)(glu)2](H2O)8}n (2), {[Cd2(TPOM)(1,4-chdc)2(H2O)4](H2O)4}n (3), {[Ni(TPOM)(suc)(H2O)2](H2O)2}n (4), and {[Zn2(TPOM)(1,4-chdc)(NO3)2](H2O)2}n (5) (TPOM = tetrakis(4-pyridyloxymethylene)methane, adi = adipic acid, glu = glutaric acid, chdc = 1,4-cyclohexanedicarboxylic acid, suc = succinic acid). These compounds were characterized by elemental analyses, IR spectroscopy and X-ray single-crystal diffraction. Compounds 1 and 3 reveal 3-fold interpenetrating 3D frameworks with sqc969 and new topologies, while compound 2 possesses a 2-fold interpenetrating 3D framework with qtz topology. Compound 4 exhibits a non-interpenetrating 3D structure with the extension of the cage structure, in which there are only two pyridine nitrogen atoms in TPOM involved in the coordination. It is different from compounds 1–3, which may take distinct coordination modes under different conditions. In compound 5, the coordination mode of TPOM is also different from those of compounds 1–3; it is a 2D structure with a 2-fold interpenetrating framework.

Syntheses, characterization, and magnetic properties of novel divalent Co/Ni coordination polymers based on a V-shaped pyridine ligand and dicarboxylate acids

Solvothermal reactions of 3,5-bis(4-pyridyl)-pyridine (BPYPY) with 1,4-benzenedicarboxylate (1,4-bdc) and trans-1,4-cyclohexanedicarboxylic acid (trans-chdc) in the presence of Co(II) and Ni(II) salts in DMF/H2O or DMA/CH3CN/H2O produced three new compounds, namely, {[Co3(BPYPY)2(1,4-bdc)3(H2O)6]}n (1), {[Ni3(BPYPY)2(1,4-bdc)3(H2O)6]}n (2), {[Co(BPYPY)(trans-chdc)0.5(NO3)]·(H2O)}n (3). These compounds were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Compounds 1 and 2 are isomorphous and present 3,4-connected 3-fold interpenetrating tfz network with a point symbol of {63}2{64·8·10}3. Compound 3 exists binuclear Co clusters which are linked by BPYPY and trans-chdc to generate a 4-connected cds network with the point symbol of {65·8} and displays antiferromagnetic characteristics. In addition, the thermal stabilities of these new compounds have also been discussed in detail.

The Mutation in the Single-Crystal Structural Transformation Process, Induced by the Combined Stimuli of Temperature and Solvent

A 2D coordination polymer containing a free ligand (Lf ), fixed by hydrogen bonds, transformed into a 3D metal-organic framework (MOF) in a single-crystal to single-crystal fashion. This transformation occurs through the combined stimuli of temperature and solvent. From 50 to 90 °C, a series of changes take place in a gradual form: the Lf is slowly moved to the cobalt center, which is accompanied by a contraction of unit cell and hydrogen bond. When the temperature rises to 95 °C, the hydrogen bond is destroyed, and Lf is suddenly combined with the cobalt ion to form an intricate 3D structure. This mutation process is irreversible and cannot occur just with the stimulus of either temperature or solvent. Notably, even under the combined stimuli, this mutation phenomena is difficult to reproduce when the solvent species and proportions change. DFT calculations were used to try to explain the nature of the phenomenon.