Song-Liang Cai

The construction of coordination networks based on imidazole-based dicarboxylate ligand containing hydroxymethyl group

Reaction of Cd(II), Fe(II), and Cu(II) with a new ligand 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid (H4hmIDC) and 4,4′-bipyridine (bpy) affords three coordination polymers of {[Cd(H2hmIDC)(bpy)]·0.5bpy·H2O}n (1), [Fe2(HhmIDC)2]n (2), and {[Cu2(ITC)(bpy)(H2O)3]·2.5H2O}n (3) (ITC = imidazole-2,4,5-tricarboxylic acid), respectively. Complex 1 and complex 3 are (4,4) nets in topological view and display in different packing mode, while hydroxymethyl group in complex 3 is oxidized to carboxylic groupin situ. Complex 2 is a rare example of a cdl-e network containing both tetrahedral and square nodes. The hydroxymethyl groups act as a precursor and undergo different reactions directed by metal ions.

Tubular metal-organic framework-based capillary gas chromatography column for separation of alkanes and aromatic positional isomers.

In this work, a tubular metal-organic framework, MOF-CJ3, with a large one-dimensional channel was chosen as stationary phase to prepare a capillary gas chromatographic column via a verified dynamic coating procedure. The column offered good separations of linear and branched alkanes, as well as aromatic positional isomers (ethylbenzene, xylene, cresol, hydroquinone, dichlorobenzene, bromobenzonitrile, chloronitrobenzene, and nitrotoluene) based on a combination of host-guest interactions and adsorption effects. Elution sequence of most of the analytes followed an increasing order of their boiling points, except for the separation of n-heptanes/isooctane, cresol, and hydroquinone isomers. Separation behavior of the column upon different organic substances may be related to the tubular pore structure of MOF-CJ3, in which the van der Waals forces between the alkanes and the hydrophobic inner surfaces might have great effect on separation of n-heptanes and isooctane, whereas the separation of cresol and hydroquinone isomers were affected by (OH⋯O) hydrogen bonds formed between the analytes and the 1,3,5-benzenetricarboxylate ligands on the pore wall. The effects of temperature on separation of aromatic positional isomers were investigated to elucidate entropy and enthalpy controlling of the separation process.

An unprecedented (3,4,14)-connected 3D metal–organic framework based on planar octanuclear lead(II) clusters as a secondary building unit

An unprecedented trinodal (3,4,14)-connected 3D metal–organic framework formed by planar octanuclear lead(II) clusters as 14-connected nodes and 2-(Pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate ligands as 3- and 4-connected nodes has been hydrothermally made. It provides a novel topological structure of metal–organic frameworks.

Anion-dependent assembly and solvent-mediated structural transformations of three Cd(II) coordination polymers based on 1H-imidazole-4-carboxylic acid

Three new Cd(II) coordination polymers with 1H-imidazole-4-carboxylic acid (Himc), [Cd(Himc)2(H2O)]n (1), [Cd(Himc)2]n (2) and [Cd2(Himc)2(SO4)(H2O)2]n (3) were perpared by solvothermal reactions and structurally characterized, which all comprised metal–negative ligand systems. Compound 1 exhibit a 1D zigzag chain; compound 2 features a 3D diamondoid work; while compound 3 possesses a 2D layer structure consisting of rhomboid grids. When 1 or 2 was left in a water/ethanolic solution of Na2SO4, their 1D or 3D framework was transformed into a 2D framework of 3. All compounds also displayed structure-related photoluminescent properties in the solid state.

The construction of Cu(I)/Cu(II) coordination polymers based on pyrazine–carboxylate: Structural diversity tuned by in situ hydrolysis reaction

The reaction of a new ligand, N,N′-(5,7-dihydro-1,3,5,7-tetraoxobenzo[1,2-c:4,5-c′]dipyrrole-2,6(1H,3H)-diyl)bis-(9CI)-3-pyrazinecarboxamide (L), with CuCl2·2H2O, CuI, or Cu(ClO4)·2H2O yields five coordination polymers. Among these polymers are three new coordination polymers, [CuII2(μ3-pzc)2(μ1-Cl)2]n (1), [CuICuII(μ2-pzc)2(μ2-Cl)(H2O)]n (2a), and {[CuI2CuII(μ2-pzc)2(μ3-I)2(H2O)]·H2O}n (3), as well as two previously reported coordination compounds, [CuICuII(μ2-pzc)2(μ2-Cl)(H2O)]n (2b) and [CuII(pzc)2] (4), in which 2-pyrazinecarboxylate (Hpzc) was obtained from in situ hydrolysis of the L ligand. Compound 1 is a two-dimensional (2D) double-layer structure, which can be viewed as a binodal (3,3)-connected network with the Schlafli symbol of (62·10) (6·102). Compounds 2a and 2b are two supramolecular isomers, both of them are (4,4) nets in topological view but showing different packing modes. Compound 3 has a 3D open framework constructed from the linkages of 1D sawtooth chains of iodide copper(I) clusters with [CuII(μ2-pzc)] subunits. Compound 4 is a mononuclear complex. Interestingly, except for compounds 2b and 4, all the other compounds cannot be directly synthesized using Hpzc and the corresponding Cu ions as initial reactants under the same reaction conditions. This finding indicates that the structural diversity of this system is tuned by the in situ hydrolysis reactions.

Construction of luminescent three-dimensional Ln(III)–Zn(II) heterometallic coordination polymers based on 2-pyridyl imidazole dicarboxylate

Four three-dimensional (3D) Ln(III)–Zn(II) heterometallic coordination polymers, {[LnZn6(μ4-mPyIDC)4Cl2(H2O)6]·Cl}n [Ln = Sm (1), Eu (2), Tb (3); H3mPyIDC = 2-(pyridine-3-yl)-1H-4, 5-imidazoledicarboxylic acid], and {[LnZn(μ5-pPyIDC)(μ2-SO4)(H2O)3]·3H2O}n [Ln = Tb (4); H3pPyIDC = 2-(pyridine-4-yl)-1H-4,5-imidazoledicarboxylic acid], were prepared under hydrothermal conditions. Isostructural complexes 1–3 were constructed using 1D [Zn3(mPyIDC)2Cl(H2O)3]n chains in a plywood-like packing mode jointed by Ln(III) ions. These compounds display unusual trinodal (3,4)-connected 3D networks with a point symbol of (4·62)4(4·63·82)4(62·82·112). Complex 4 has a highly connected framework with (36·422·516·6) network topology based on a rare planar heterometallic hexanuclear [Tb2Zn4(pPyIDC)2] secondary building block. The luminescent properties of complexes 2–4 were also investigated.

An unprecedented supramolecular network with channels filled by 1D coordination polymer chains: Cocrystallization of Ag(I)-4,4′-bipyridine and Ag(I)-benzimidazole complexes

An unprecedented supramolecular network formed by [Ag(4,4′-bipyridine)]n chains and [Ag(NO3)4]3− anions via Ag⋯O interaction shows four types of channels filled by [Ag(4,4′-bipyridine)]n chains, [Ag(benzimidazole)]n chains and water molecules, representing the first example of cocrystallization of two 1D infinite coordination polymer chains.

Spontaneous resolution of a coordination polymer containing stereogenic five-coordinate Zn(II) centers and achiral ligands with axially chiral conformation

A pair of chiral coordination polymers, [Zn(HPyIDC)]n (1a and 1b, H3PyIDC = 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate), were assembled from an achiral precursor, H3PyIDC and Zn(II) ions via spontaneous resolution under solvothermal conditions. Crystal structure analysis showed that they are chiral three-dimensional (3D) coordination polymers based on the interconnection of six types of one-dimensional (1D) helical chains. They exhibit an intrinsic chiral (10,3)-a network. The chirality comes from both the stereogenic five-coordinate Zn(II) ions and the axially chiral ligands. Solid-state circular dichroism (CD) spectra measurements confirmed the occurrence of spontaneous resolution of [Zn(HPyIDC)]n and demonstrated that the resulting crystal of [Zn(HPyIDC)]n is a racemic mixture. Compound 1 showed strong fluorescence emission at room temperature.

Two new three-dimensional metal–organic frameworks with 4-connected diamondoid and unusual (6,16)-connected net topologies based on planar tetranuclear squares as secondary building units

Solvothermal reactions of Co2+ and Mn2+ salts with 2-(trifluoromethyl)-1H-4,5-imidazole dicarboxylic acid (H3TFMIDC) lead to two novel three-dimensional (3D) metal–organic frameworks (MOFs), namely, [Co6(μ3-TFMIDC)4(H2O)12]·15H2O (1) and [(Me2NH2)3][MnII6 MnIII(μ3-TFMIDC)6(H2O)6]·18H2O (2). Single-crystal X-ray diffraction analysis reveals that both of them are based on interesting planar tetranuclear squares [M4(TFMIDC)4] as secondary building units (SBUs). Compound 1 exhibits a unique 3D two-fold interpenetrated network with the diamondoid topology consisting of the tetranuclear square SBUs as 4-connected nodes, while compound 2 features an unusual (6,16)-connected 3D framework based on the novel tetranuclear square SBUs as 16-connected nodes and trivalent manganese ions as 6-connected nodes, representing the first 16-connected MOF utilizing planar tetranuclear square SBUs as building blocks. Our results open up new perspectives to design novel 3D extended MOFs, especially the unique highly connected 3D MOFs by employing planar tetranuclear square SBUs. Moreover, IR spectroscopy, powder X-ray diffraction, thermogravimetric analyses, and a study on the magnetic properties of both compounds, have been also performed.

Construction of a hydrazone-linked chiral covalent organic framework–silica composite as the stationary phase for high performance liquid chromatography

Covalent organic frameworks (COFs), as an emerging class of crystalline porous organic polymers, have great potential for applications in chromatographic separation owning to their fascinating crystalline structures and outstanding properties. However, development of COF materials as novel stationary phases in high performance liquid chromatography (HPLC) is just in its infancy. Herein, we report the design and construction of a new hydrazone-linked chiral COF, termed BtaMth COF, from a chiral hydrazide building block (Mth) and present a one-pot synthetic method for the fabrication of BtaMth@SiO2 composite for HPLC separation of isomers. The as-synthesized BtaMth chiral COF displays good crystallinity, high porosity, as well as excellent chemical stability. Meanwhile, the fabricated HPLC column by using BtaMth@SiO2 composite as the new stationary phase exhibits high resolution performances for the separation of positional isomers including nitrotoluene and nitrochlorobenzene, as well as cis-trans isomers including beta-cypermethrin and metconazole. Additionally, some effects such as the composition of the mobile phase and column temperature for HPLC separations on the BtaMth@SiO2 packed column also have been studied in detail. The successful applications indicate the great potentials of hydrazone-linked chiral COF-silica composite as novel stationary phase for the efficient HPLC separation.