Guang-Zhen Liu

The Cd(II)–L carboxylate motifs mediated by the bpp ligand afforded a topologically new coordination polymer by hydrothermal reaction, namely, [Cd₂(L)(bpp)₂(H₂O)₂]·2H₂O ([1·(H₂O)₂]·2H₂O) (H₄L = 5-(2,3-Dicarboxy phenoxy)isophthalic acid and bpp = 1,3-bis(4-pyridyl)propane). It is further characterized by elemental analysis, IR, thermogravimetric analysis (TGA) and fluorescence analysis. The single crystal X-ray diffraction revealed that the structure features the Cd(II)-carboxylate layer motifs cross-linked by the bpp coligands to construct a 3D metal-organic framework with a (4,4,4)-connected {4.5.6².7.8} {4.5².6².8}{5².6².7.8} new framework topology. The TGA shows that the compound exhitits good thermal properties with reversible dehydrated-rehydrated ability without destroying the framework integrity. In addition, the dehydration/rehydration process is accompanied with a unusual phenomenon of fluorescence transfer, which makes it great potential in minimum moisture detection.

The Cd(II)-L carboxylate motifs mediated by the bpp ligand afforded a topologically new coordination polymer by hydrothermal reaction, namely, [Cd2(L)(bpp)2(H2O)2]·2H2O ([1·(H2O)2]·2H2O) (H4L = 5-(2,3-Dicarboxy phenoxy)isophthalic acid and bpp = 1,3-bis(4-pyridyl)propane), which was further characterized by elemental analysis, IR, thermogravimetric analysis (TGA) and fluorescence analysis. The single-crystal X-ray diffraction revealed that the structure features the Cd(II)-carboxylate layer motifs cross-linked by the bpp coligands to construct a 3D metal-organic framework with a (4,4,4)-connected {4.5.62.7.8}{4.52.62.8}{52.62.7.8} new framework topology. The TGA shows that the compound exhitits good thermal properties with reversible dehydrated-rehydrated ability without destroying the framework integrity. In addition, the dehydration/rehydration process is accompanied with a unusual phenomenon of fluorescence transfer, which makes it great potential in minimum moisture detection.

Two novel zinc(II) coordination polymers, namely [Zn₂(ptca)(OH)(bpe)(H₂O)]_n (1) and {[Zn(Hptca)(bpa)]·H₂O}_n (2) (H₃ptca is 1,3,5-pentanetricarboxylic acid, bpe is 1,2-bis(4-pyridinyl)ethylene, bpa is 1,2-bis(4-pyridinyl)ethane) have been prepared through solvothermal reactions. Single-crystal X-ray diffraction revealed that both complexes 1 and 2 have two-dimensional layer structures pillared by nitrogen-donor ligands, wherein different degrees of deprotonation and coordination modes of carboxylate groups are observed. In addition, the fluorescent properties of complexes 1 and 2 have been studied in the solid state at room temperature.

Solvothermal reactions of the flexible multicarboxylate ligand methylenebis(thioglycolic acid) (H₂mbta) with Mn/Zn salts in the presence of 1,4-bis(1-imidazoly)benzene (bib) and 3, 5-bis(1-imidazoly)pyridine (bip) afforded two novel 2D layer coordination polymers [Mn(mbta)(bib)]_n (I) and {[Zn(mbta)(bip)](H₂O)}_n (II) (CCDC nos. 2404028 (I), 2404045 (II)). The 2D layer structure of I features dinuclear manganese(II) unit joined by a pair of H₂mbta ligands, whereas the 2D layer of II manifests that the flexible multicarboxylate H₂mbta ligand directly bridges mononuclear zinc(II) unit. Furthermore, powder X-ray diffraction analysis, thermal degeneration, magnetic property of complex I and luminescence property of complex II are also investigated.

A novel Y-shaped ligand 2,2'-(5-((1H-1,2,4-triazol-1-yl)methyl)-1,3-phenylene)bis(2-methyl propionic acid) (H₂L) and its Ni(II) coordination polymer were synthesized under appropriate conditions. Their structures were characterized by single-crystal X-ray diffraction and other physicochemical techniques. The Ni(II) coordination polymer shows an infinite 1D cage structure along the a direction.

Two new coordination polymers [Zn(L)(Bpa)·H₂O]_n (I) and [Zn(L)(Bip)]_n (II) (H₂L is 4‑hydroxyisophthalic acid, Bpa is 1,2-bis(4-pyridyl)ethane, Bip is 3,5-bis(imidazole-1-yl)pyridine) have been prepared and characterized by element analysis, powder X-ray diffraction, and single-crystal X-ray diffraction (CCDC nos. 2073592 (I), 2073594 (II)). The single crystal X-ray diffraction studies reveal that compound I is a 1D chain structure, in which zinc(II) is four-coordinated with a tetrahedral geometry. Complex II is a 2D layer structure, in which zinc(II) is four-coordinated. Complexes I and II are further extended into three-dimensional supramolecular network via hydrogen bonds and π···π interactions. The solid-state luminescent properties of compounds I and II have been investigated.

A Zn(II) coordination polymer, {[Zn(ca)(bpe)]·0.5H₂O}_n (H₂ca = citraconic acid, bpe = 1,2-bi(4-pyridyl)ethylene) has been prepared by hydrothermal reaction, and characterized by single-crystal X-ray diffraction, elemental analysis, FT IR, PXRD, and TGA. Title compound exhibits a three-dimensional metal-organic framework with lvt topology type and 4²⋅8⁴ Schläfli symbol. The compound has good phase purity and high thermal stability. The emission spectrum of the complex is similar to that of the powdered free bpe molecule, but the obvious red-shift may be due to the coordination of bpe with Zn ions, resulting in a reduced nonradiative decay of the intraligand excited state. The center-to-center olefin bond distance of bpe ligand in the compound, 3.620 Å, is suitable to undergo [2+2] cycloaddition reaction. The ¹H NMR spectrum of the cycloaddition product after UV irradiation for 24 h shows that the double bonds were partially photodimerized (82.6%) into the rctt-tpcb and rtct-tpcb derivatives.

Two new coordination polymers, {[Zn(3-Nbdc)(bip)]·2H₂O}_n (1) and {[Co(3-Nbdc)(bip)(H₂O)]0.25H₂O}_n (2) (H₂3-Nbdc = 3-nitrobenzene-1,2-dicarboxylic acid, bip = 3,5-bis(1-imidazolyl)pyridine) were synthesized under the hydrothermal conditions and characterized by single crystal X-ray diffraction and elemental analysis. In 1, the Zn(II) ion forms a slightly distorted [ZnO₂N₂] tetrahedron by two carboxylate oxygen atoms and two nitrogen atoms. Adjacent Zn(II) neighbors are linked by 3-Nbdc dianions adopting monodentate coordination mode to form 1D Zn-carboxylate chain, which is further extended by bip molecules to produce a two-dimensional thick layer. For complex 2, two six-coordinated Co(II) ions with different coordination environments are alternately connected by 3-Nbdc dianions and bip ligands along different directions to generate a two-dimensional grid layer. Furthermore, Powder X-ray diffractions, FTIR spectra and thermogravimetric analyses are also investigated.