Cui-Hong He

Two metal–organic frameworks with unique high-connected binodal network topologies: synthesis, structures, and catalytic properties

{[Cd3(btec)(btx)0.5(μ3-OH)(H2O)]·H2O}n (1) and [Cu2(btec)(btx)1.5]n (2), two novel cadmium(II) and copper(II)-based high-connected metal–organic frameworks, with both 1,2,4,5-benzenetetracarboxylate (btec) and 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (btx) as mixed ligands were hydrothermally synthesized and structurally characterized. Both MOFs have three-dimensional (3D) structures, but different framework topologies and ligand linkage modes. 1 possesses an unprecedented binodal (4,12)-connected topology structure, in which the ligand btec serves as a rare dodecadentate and ordinary octadentate in two types of coordination modes. Meanwhile, 2 exhibits a binodal (4,7)-connected topological network with an enneadentate coordination geometry of the btec ligand. Both MOFs provide novel examples of designing and synthesizing novel binodal MOFs, and demonstrate that the 1,2,4,5-benzenetetracarboxylic acid ligand with rich coordination chemistry information is useful in the construction of binodal highly-connected nets. In addition, the catalytic performance of 2 has also been checked. 2 is active as a catalyst for the degradation of methyl orange.

From discrete dinuclear to 1-D and 2-D structures: nickel dipicolinate complexes with flexible bis(imidazole) ligands

Three new complexes, [Ni2(dpc)2(L1)2(H2O)2] · 4H2O (1), [Ni(dpc)(L2)1.5] n (2), and {[Ni(dpc)(L3)1.5] · 2H2O} n (3), where H2dpc = dipicolinic acid, L1 = 1,4-bis(2-methylimidazol-1-yl)butane, L2 = 4,4′-bis(2-methylimidazol-1-ylmethyl)biphenyl, and L3 = 1,4-bis(benzimidazol-1-yl)-2-butylene, have been synthesized by hydrothermal methods and characterized by elemental analyses, infrared spectra, thermogravimetric analysis, and X-ray crystallography. The common structural characteristic of the three complexes is that the Ni2+ is coordinated by tridentate dipicolinate through nitrogen of pyridine and oxygen of carboxylate, serving as a terminal ligand. In 1, two L1 link two [Ni(dpc)(H2O)] units to a discrete binuclear metallomacrocycle with a 22-membered ring, which is assembled through multiple O–H ··· O hydrogen bonds to form a 3-D supramolecular framework. Complex 2 exhibits a 1-D ladder-like chain structure constructed by cis/trans-conformation L2 linking metal centers; 3 displays a 2-D (6,3) topology, being constructed from the linking of [Ni(pdc)] by L3. These results indicate the merits of flexible bis(imidazole) ligands as building blocks with dipicolinate for the construction of complexes with diverse structural motifs.

Syntheses, structures, and photoluminescence of three cadmium(II) coordination polymers with flexible bis(benzimidazole) ligands

Three cadmium(II) coordination polymers, [CdBr2(L1)] n (1), [CdI2(L2)] n (2), and Cd2Br4(L3)2 (3), where L1 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L2 = 1,4-bis(5,6-dimethylbenzimidazole)butane, and L3 = 1,6-bis(5,6-dimethylbenzimidazole)hexane, have been synthesized by hydrothermal methods and characterized by elemental analyses, IR spectra, TGA, PXRD, and X-ray crystallographic diffraction. Complex 1 contains a 1-D helical chain in which CdBr2 units are linked by L1. For 2, each CdI2 is connected by two different conformations of L2 to form a 1-D zigzag chain. For 3, each CdBr2 is linked by L3 bridges to afford a binuclear structure. These results indicate that the spacer length of the ligands play important roles in assembly of Cd(II) coordination polymers. Thermogravimetric analyses and solid-state luminescent properties of the complexes have also been investigated.

Synthesis, structures, and fluorescence of two cadmium(II) coordination polymers with a semirigid bis-benzimidazole

Compounds [CdLCl2] n (1) and {[Cd(L)2(ClO4)]·ClO4} n (2), where L = 1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, have been synthesized by hydrothermal method, and characterized by element analysis, IR spectra, Powder XRD, and X-ray crystallographic diffraction. Cd(II) in 1 and 2 are both trigonal bipyramidal. Different cadmium salts of chloride and perchlorate lead to different configurations of [Cd2L2]2+, trans-form in 1 but trans and cis-forms in 2. The 1-D beaded chains of 1 are further linked to generate a 3-D supramolecular architecture by strong π–π stacking interactions as well as intermolecular C–H ··· Cl hydrogen bonds. In 2, the 1-D beaded chains are further assembled by intermolecular C–H ··· O hydrogen bonds to form a 2-D layer. Solid-state fluorescent properties of 1 and 2 were investigated at room temperature.

Synthesis, Structures, and Catalytic Properties of Two Silver(I) Coordination Polymers Constructed from 1,4-Bis(benzimidazolyl)butane

Using a hydrothermal synthesis method, two silver(I) complexes, [Ag(bbbm)(1,3-HBDC)]n (1) and [Ag(bbbm)(1,2-HBDC)]n (2) (bbbm = 1,1´-(1,4-butanediyl)bis-1H-benzimidazole, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, 1,2-H2BDC = 1,2-benzenedicarboxylic acid), have been synthesized and characterized by elemental analysis, IR spectra, thermogravimetric (TG) analysis and singlecrystal X-ray diffraction. The silver centers display different environments with a distorted T-shaped geometry in 1, and a linear geometry in 2. Both chain structures of 1 and 2 are bridged by bbbm in a bis-monodentate coordination mode. 1 is further linked to generate a 3D supramolecular architecture via p-p stacking interactions and intermolecular O-H· · ·O hydrogen bonding. In 2, the ribbon-like chains are additionally assembled by two p-p stacking modes to form a layer motif. The photoluminescence of 1 and 2 was investigated in the solid state. 1 and 2 possess a remarkable activity for degradation of methyl orange by persulfate in a Fenton-like process. Graphical Abstract Synthesis, Structures, and Catalytic Properties of Two Silver(I) Coordination Polymers Constructed from 1,4-Bis(benzimidazolyl)butane

Synthesis, Structure, and Characterization of a Novel One-Dimensional Mixed-Ligand Coordination Polymer of Copper(II)

A novel Cu(II) mixed-ligand complex, {[Cu(sq)(L)(H2O)]· 0.9H2O}n (1) (sq = squarate dianion, L = 5,5′-dimethyl-2,2′-bipyridine), has been synthesized and characterized by elemental analyses, infrared (IR), and X-ray single-crystal diffraction. In 1, each copper(II) ion has a five-coordinated environment with square pyramidal geometry. A one-dimensional (1D) chain structure of the complex is constructed by squarate in μ-1,2-bis(monodentate) coordination mode and further forms a two-dimensional (2D) framework via “metal chelate–metal chelate ring” π–π stacking interactions between the adjacent chains. This unexpected π–π stacking interaction provides structural evidence for the metalloaromaticity of the Cu(II)-(aromatic α,α′-diimines) chelate rings.