Xiao-Qiang Yao

Syntheses, structures, photoluminescence and magnetic properties of four new metal–organic frameworks based on imidazole ligands and aromatic polycarboxylate acids

Four metal–organic coordination polymers, {[Cu2(4,4′-bibp)2(NO2)3)]·(NO2)(H2O)}n (1), [Cd(bdc)(4,4′-bibp)]n (2), {[Co2(bdc)2(4,4′-bibp)3(H2O)2]·(H2O)2}n (3), [Zn(Hbtc)(1,4-bix)]n (4) (4,4′-bibp = 4,4′-bis(1-imidazolyl)biphenyl; 1,4-bix = 1,4-bis((1H-imidazol-1-yl)methyl)benzene; H2bdc = 1,4-benzenedicarboxylate; H3btc = 1,3,5-benzenetricarboxylate) were obtained under hydrothermal conditions and characterized structurally. X-Ray diffraction analysis reveals that the four complexes exhibit new frameworks due to diverse coordination conformations. In copper compound 1, with mixed-valence copper(II)–copper(I), rigid linear 4,4′-bibp ligands connect two adjacent layers and the whole structure is a three-dimensional 6,6-connected network. In cadmium compound 2, 4,4′-bibp and bdc anions as bidentate ligands coordinate to cadmium cations to form a three-dimensional 4,4-connected network with a 3-fold interpenetrating framework. In cobalt compound 3, 4,4′-bibp and bdc anions also act as bidentate ligands, and coordinate to cobalt cations to form a three-dimensional 4,6-connected network. Zinc compound 4 shows that both the 1,4-bix ligand and btc anions act as bidentate bridging ligands, and connect the zinc cations to give a 2D polycatenated array structure. The magnetic properties for copper compound 1 and luminescent properties for cadmium compound 2 and zinc compound 4 are also discussed in detail.

Syntheses, structures, magnetic and photoluminescence properties of metal–organic frameworks based on aromatic polycarboxylate acids

Six new coordination compounds, namely [Co(H2bptc)]n (1), [Mn(H2bptc)]n (2), [Cd2(bptc)(phen)2(H2O)2]n (3), [Eu2(cpa)3(DMF)2]n (4), [Nd2(cpa)3(DMF)2]n (5) and [Pr2(cpa)3(DMF)2]n (6) (bptc4− = biphenyl-2,2′,4,4′-tetracarboxylate anion, phen=1,10-phenanthroline, cpa2− = 4-chloroisophthalic acid anion) were synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and thermogravimetric analysis. Co and Mn compounds are isostructural, and possess a three-dimensional 5, 5-connected network. In Cd compound, multicarboxylate ligand H4bptc link Cd centers to generate a two-dimensional 4, 4-c net structure with phen acting as terminal ligand. Eu, Nd, and Pr compounds have similar structures, and cpa2− ligands link lanthanide cations to generate a two-dimensional sheet structure. Magnetic susceptibility measurements indicate that the Co compound has a dominating ferromagnetic coupling between Co(II) ions, and Mn compound exhibits antiferromagnetic coupling between Mn(II) ions. Furthermore, their luminescent properties are also determined in the solid state at room temperature.

Unusual three-dimensional coordination networks with [WS4Cu6] cluster nodes and α-C3N4 topology

Two new 3D frameworks [(WS4Cu6Br4)(timp)8/3(H2O)40/3]n (1) and [(WS4Cu6Br4) (timtz)8/3(H2O)40/3]n (2), containing heptanuclear cluster blocks (one W atom and six Cu atoms) bridged by trigonal ligands timp or timtz (timp = 1-(3,5-di (1H-imidazol-1-yl)phenyl)-1H-imidazole; timtz = 2,4,6-tri(1H-imidazol-1-yl)-1,3,5-triazine), were successfully synthesized. Both compounds were characterized by single-crystal X-ray diffraction, elemental analysis, XRD, IR, TGA. X-ray determination shows that 1 and 2 can be topologically represented as (3,4)-connected networks with α-C3N4 (or ctn) topology where [WS4Cu6] act as the 4-connecting nodes, and the timp or timtz ligands bridge in pairs that act as the three-connecting nodes. Both compounds have the high symmetry of space group I-43d, which is the maximum symmetry for this net topology. The luminescent spectra and N2 absorption behaviors for 1 and 2 have also been investigated.

Application of W–Cu–S-based secondary building units in functional metal–organic frameworks

This highlight discusses the structures and functions of W–Cu–S cluster polymers divided into different multinuclear cluster units. Great strides have been made in the potential applications of W–Cu–S cluster polymers in advanced materials, including third-order non-linear optics (NLO), gas absorption and solvatochromic effects, in the past few years. Finally, we suggest some opportunities to further improve the depth of the related research.

The synthesis, structure and third-order nonlinear optical effect of a new 2D cluster polymer based on a [WS4Cu4]2+ SBU and 1,2-di(pyridin-4-yl)ethane

The self-assembly reaction of a multinodal preformed cluster with 1,2-di(pyridin-4-yl)ethane as the organic ligand afforded the 2D cluster polymer (1), {[(WS4Cu4)I2(dpe)2](DMF)4}n. There is a cavity between each two nearby dpe ligands in 1. The [WS4Cu4]2+ units are fixed by I− ions, which is attributed to the multinodal feature of the W–S–Cu secondary building units, and therefore, the cavities in 1 are settled. The NLO properties show that 1 exhibits an optical self-focusing behavior and reverse saturable absorption effects. This work provides us with useful clues to further explore the 2D W–Cu–S-based cluster polymer with cavities.