Aixiang Tian

Self-assembly of nanometre-scale metallacalix[4]arene building blocks and Keggin units to a novel (3,4)-connected 3D self-penetrating framework

A novel (3,4)-connected 3D self-penetrating metal-organic framework with a nanometre-scale cavity constructed from metallacalix[4]arene building blocks and Keggin-type polyanions has been obtained by using a 1,3-bis(1-methyl-5-mercapto-1,2,3,4-tetrazole)propane ligand.

Unprecedented Application of Flexible Bis(pyridyl-tetrazole) Ligands To Construct Helix/Loop Subunits To Modify Polyoxometalate Anions

By introducing the unprecedented and flexible isomeric bis(pyridyl-tetrazole) ligands into a polyoxometalates (POMs) system, three POM-based compounds, {Ag2(4-bptzb)2(H2O)2[H2PMo12O40]2}·4-bptzb·5H2O (1), [Ag4(3-bptzb)2(PMo(V)Mo(VI)11O40)]·2H2O (2), and Ag3(3-bptzb)2.5(H2O)2[H3P2W18O62] (3) [4-bptzb = 1,4-bis(5-(4-pyridyl)tetrazolyl)butane and 3-bptzb =1,4-bis(5-(3-pyridyl)tetrazolyl)butane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses. Compound 1 exhibits a dimeric structure constructed from two Keggin [PMo12O40](3-) anions and a binuclear [Ag2(trans-4-bptzb)2](2+) subunit in which the trans-4-bptzb acts as a bidentate bridging ligand with one tetrazolyl group. In 2, the 3-bptzb acts as a tetradentate bridging ligand with the tetrazolyl and pyridyl groups linking Ag(I) ions to generate a 3D metal-organic framework (MOF), which contains charming meso-helix chains. The Keggin anions acting as bidentate inorganic ligands reside in the distorted tetragonal channels of the MOF. In compound 3, the 3-bptzb adopts versatile coordination modes linking Ag(I) ions to first construct loop connecting loop 1D chains, which are linked by {Ag[P2W18O62]}n zigzag chains to form a scarce hamburger-style 2D sheet. These adjacent sheets are further fused by 3-bptzb ligands to construct a 3D framework. The influences of isomeric bptzb ligands and POMs on the construction of Ag-bptzb subunits and the whole structures of the title compounds are discussed. The electrochemical behaviors and electrocatalytic activities of compounds 2 and 3 and their corresponding parent POMs as well as the fluorescent properties of the title compounds have been studied in detail. In addition, the photocatalytic activities of compounds 2 and 3 and their corresponding parent POMs for decomposition of methylene blue, rhodamine B, and methyl orange under UV irradiation have also been investigated.

The design and construction of a series of metal–organic coordination polymers based on two isomeric semi-rigid bis-pyridyl-bis-amide ligands and three aromatic polycarboxylates

A series of metal–organic coordination polymers, namely, {[Cu3(4-bpah)4(1,3,5-BTC)2]·8H2O}n (1), {[Cu3(4-bpah)3(1,2-BDC)3(H2O)2]·4H2O}n (2), {[Cu(4-bpah)(1,3-BDC)(H2O)]}n (3), {[Co(4-bpah)(1,3-BDC)(H2O)]}n (4), {[Ni(4-bpah)(1,3-BDC)(H2O)]}n (5), {[Zn(4-bpah)(1,3-BDC)(H2O)]}n (6), {[Cd(4-bpah)(1,3-BDC)]}n (7), {[Cd(3-bpah)(1,3-BDC)]·H2O}n (8), {[Cu2(3-bpah)(1,3-BDC)2]·H2O}n (9), where 4-bpah = N,N′-bis(4-pyridinecarboxamide)-1,2-cyclohexane, 3-bpah = N,N′-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid, 1,2-H2BDC = 1,2-benzenedicarboxylic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, have been synthesized under hydrothermal conditions. The structures of 1–9 have been determined by single crystal X-ray diffraction analyses and further characterized by infrared spectroscopy (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Complex 1 displays a 2D (42·83·10)(43·62·8)4(4)2 topological network. Complex 2 shows a 2D (3·4·5·62·7)2(3·42·52·7) topological framework that contains tri-flexural and left-hand helix chains. Complexes 3–6 reveal a similar 2D sql network with (44·62) topology. Complexes 7 and 8 show two different 2D double-layer structures with (42·6)(43·6·84·102)(4) and (42·6·86·12)(42·6)(8) topology, respectively. Complex 9 exhibits a new 3D 3-nodal topology with the Schlafli symbol (4·62)2(42·64)2(42·68·82·103). The successful construction of complexes 1–9 implies that using semi-rigid bis-pyridyl-bis-amide ligands can obtain various architectures with small voids. The effect of the isomeric semi-rigid bis-pyridyl-bis-amide ligands and the three aromatic polycarboxylates, as well as the central metal ions on the formation and structures of the title coordination polymers have been discussed. The fluorescent and photocatalytic properties of complexes 1–9 have also been investigated.

Construction and properties of cobalt(II)/copper(II) coordination polymers based on N-donor ligands and polycarboxylates mixed ligands

Metal–organic coordination polymers (MOCPs) are well known organic–inorganic hybrids with infinite structures consisting of metal ions/clusters and organic ligands linked through coordination interactions. MOCPs can be constructed from one or more than one organic bridging ligands (mixed-ligands) and different metal ions. The previous reports prove the fact that the nature of organic ligands and metal ions dominates the final structures as well as properties of the MOCPs in a certain way. Therefore, we focus on discussing the cobalt(II)/copper(II) coordination polymers constructed from the mixed-ligands of polycarboxylates and N-donor ligands, which may possess potential applications in the fields of electrochemistry, electrocatalysis, magnetism and photocatalysis. In this review, we summarize some typical Co(II)/Cu(II) MOCPs based on the mixed bridging organic ligands, aiming to discuss their versatile synthesis methods, topologies and structural influence factors, as well as their tunable properties. All of these aspects are highlighted in this review, which seeks to guide further investigations of cobalt(II)/copper(II) coordination polymers.

Assembly and property of four 2D layer-like coordination polymers with different structural features derived from bis(3-pyridylformyl)piperazine ligand and aromatic dicarboxylic acids with nitro group

Using the mixed ligands bis(3-pyridylformyl)piperazine (3-bpfp) and 5-nitroisophthalic acid (H2NIPH) or 3-nitrophthalic acid (H2NPH), four two dimensional (2D) copper or cadmium coordination polymers with different structural features formulated as [Cu(3-bpfp)(NIPH)(H2O)] (1), [Cu(3-bpfp)0.5(NPH)(H2O)2] (2), [Cd(3-bpfp)0.5(NIPH)] (3), and [Cd(3-bpfp)(NPH)(H2O)]·H2O (4) have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses indicate that complex 1 displays a new contorted 2D layer consisting of two kinds of tetranuclear cycles with different dimensions: A-cycle of 20.53 × 9.57 A and B-cycle of 19.17 × 12.07 A, in which CuII ions are knitted by the 3-bpfp ligands with μ2-bridging coordination mode (via ligation of nitrogen atoms in pyridyl rings) and NIPH. In complex 2, CuII centers are connected by the ligands NPH to form one dimensional (1D) CuII-NPH left- and right-handed helical chains, and these chains are extended into 2D layer network by the 3-bpfp ligands with μ2-bridging coordination mode. Only one hexanuclear cycle with dimension of 16.86 × 11.10 A was included in the 2D structure of 2. Complex 3 contains two types of 1D ladder-like chains composed of CdII ion, the 3-bpfp ligand with μ4-bridging coordination mode (via ligation of nitrogen atoms in pyridyl rings and oxygen atoms in carbonyl groups) and bridging NIPH ligand with two coordination modes (chelate-monodentate mode and chelate mode), forming a double layer 2D network with the (42·6)(42·84)(47·63) topology. Complex 4 possesses 2D sheet based on the 1D right-handed helical chains constructed from the CdII ions and the NPH ligands with bis-chelating coordination mode, and the 3-bpfp ligands with μ2-bridging coordination mode. Moreover, the 2D structures of complexes 1–4 are ultimately packed into three dimensional (3D) supramolecular frameworks through the hydrogen bonding or the π–π stacking interactions. In addition, the fluorescent properties of the title complexes and the electrochemical behaviors of 1–2 at room temperature have been investigated.

A series of 3D PW12O403−-based AgI–bis(triazole) complexes containing different multinuclear loops: syntheses, structures and properties

Four [PW12O40]3− (PW12)-based inorganic–organic hybrid compounds constructed from AgI ions and flexible bis(triazole) ligands with different spacer lengths, [Ag8(btp)4(H2O)2(HPWVI10WV2O40)2]·H2O (1), [Ag4(btb)2(HPWVI10WV2O40)] (2), [(btb)(H3PW12O40)]·6H2O (3) and [Ag5(btx)4(PWVI10WV2O40)] (4), (btp = 1,3-bis(1,2,4-triazol-1-yl)propane, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, btx = 1,6-bis(1,2,4-triazol-1-yl)hexane), have been successfully isolated in the pH range 0.5–2.0 under hydrothermal conditions and characterized by single crystal X-ray diffraction analysis. In compound 1, the btp with a shorter spacer –(CH2)3– was used, and the 2D AgI–btp wave layers containing tetra-nuclear loops have been obtained, which were further extended into a 3D hamburger-style framework by two types of PW12 inorganic linkages. In compound 2, the btp ligand was replaced by btb with a longer spacer –(CH2)4–, thus a 2D AgI–btb grid layer containing two types of multinuclear loops was obtained. The PW12 anions reside in the void of a large hexa-nuclear loop and as octa-dentate inorganic linkages connect these 2D grid layers to construct a 3D framework. Compound 3 was synthesized under the same conditions as 2 except for a different crystallization time, which only exhibits a supramolecular structure constructed from protonated PW12 and btb molecules. The btx molecule with the longest –(CH2)6– spacer was utilized in compound 4, an interesting 3-fold interpenetrating 2D AgI–btx network containing large dodeca-nuclear loops formed, which was further linked by the six-connected PW12 anions to construct a 3D skeleton. The influences of –(CH2)n– spacers as well as the pH value and crystallization time on forming and tuning different 3D AgI/POM-based compounds containing different multinuclear loops have been discussed. Moreover, the electrochemical properties and photochemical catalysis of these four compounds have also been investigated.

A 3D organopolymolybdate polymer with unusual topology functionalized by 1,4-bis(1,2,4-triazol-1-yl)butane through Mo–N bond

An unusual (4,6,6)-connected high dimensional organopolymolybdate polymer by 1,4-bis(1,2,4-triazol-1-yl)butane coordinating directly to a molybdenum atom has been obtained under hydrothermal condition, which exhibits a self-penetrating framework with (44·5·6)(45·54·66)(48·52·65) topology assembled from 2D self-threading skeleton.

Three 3D silver-bis(triazole) metal–organic frameworks stabilized by high-connected Wells–Dawson polyoxometallates

Three silver-bis(triazole) three-dimensional (3D) metal-organic frameworks (MOFs) with Wells-Dawson type polyoxometalates (POMs) as high-connected inorganic ligands have been isolated: [Ag7(bte)4(H2O)(HP2W(VI)16W(V)2O62)]·2H2O (1), [Ag7(btp)5(HP2W(VI)16W(V)2O62)]·H2O (2) and [Ag4(btb)3.5(P2W18O62)](H2btb)·2H2O (3) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane, btp = 1,3-bis(1,2,4-triazol-1-y1)propane, btb = 1,4-bis(1,2,4-triazol-1-y1)butane). Compound 1 contains a 3D metal-organic subunit, which is constructed from 1D Ag/bte chains and 2D layers based on hexanuclear [Ag6(bte)2](6+) circuits. The [P2W18O62](8-) (P2W18) anions act as 10-dentate inorganic ligands incorporated into the channels of the 3D framework. In compound 2, the metal-organic subunits are a 2D layer constructed from the [Ag5(btp)2](5+) circuits and flexible Ag/btp helical chains. The P2W18 anions also act as 10-dentate inorganic ligands linking adjacent 2D layers to construct a 3D framework. Both 1 and 2 contain Ag-Ag bonds, which further stabilize the structures. Compared with 1 and 2, the metal-organic subunit of 3 is a 3D cage-like host architecture. Without the assistance of Ag-Ag bonds, two sets of these 3D MOFs interpenetrate each other to generate a 2-fold interpenetrating structure for stability, which are united by the 5-dentate P2W18 anions to construct an integrated 3D structure. The roles of coordination modes of silver centers and POMs, as well as the effects of organic ligand lengths on the metal-organic subunit and final structures, have been reported. In addition, the electrochemical properties, photochemical catalysis and antibacterial properties of title compounds have also been investigated.

Architectural chemistry of polyoxometalate-based coordination frameworks constructed from flexible N-donor ligands

Polyoxometalate-based coordination frameworks (POMCFs) extend the families of material chemistry and structural chemistry due to their diverse properties and fascinating architectures. In the architectural field of POMCFs, the choice of organic ligand usually plays a key role in the self-assembling process. To date, plenty of organic ligands, such as carboxylates and N-donor ligands, have been designed and utilized in the construction of porous, multinuclear and polythreaded architectures. As far as N-donor ligands are concerned, their flexible and rigid nature can show important influences on the formation of various architectures. This perspective highlights the recent developments in polythreaded/penetrating, multinuclear, helical architectural chemistry of POMCFs constructed from flexible N-donor ligands, including bis-imidazole, bis-triazole, bis-pyridine, bi-mercaptotetrazole, bi-pyridyl-bis-amide and bis-pyridyltetrazole ligands. Here, we will describe the influence of different space lengths and coordination groups on flexible N-donor ligands, as well as the influence of pH and polyoxometalates on the architectural structures of POMCFs, which may offer some possible synthetic strategies for constructing functional POMCFs with novel architectures.

Copper(II) metal–organic networks derived from bis(pyridylformyl)piperazine ligands and aromatic polycarboxylates: 2D layered structures and a novel 3,5-connected binodal 3D topology

Three novel coordination polymers [Cu2(3-bpfp)(BDC)2(H2O)2]·4H2O (1), [Cu(3-bpfp)(HBTC)]·0.5H2O (2) and [Cu(4-bpfp)0.5(HBTC)(H2O)] (3) have been hydrothermally synthesized by self-assembly of aromatic polycarboxylate ligands H2BDC (H2BDC = 1,3-benzenedicarboxylate acid) or H3BTC (H3BTC = 1,3,5-benzenetricarboxylate acid), bridging ligands 3-bpfp/or 4-bpfp [3-bpfp = bis(3-pyridylformyl)piperazine, 4-bpfp = bis(4-pyridylformyl)piperazine], and copper chloride. X-Ray diffraction analysis reveals that each CuII ion is connected by BDC/or HBTC and 3-bpfp/or 4-bpfp ligands to form two dimensional (2D) layer structures in compounds 1 and 3. Ligands 3-bpfp and 4-bpfp both display μ4-bridging coordination mode in 1 and 3 (via ligation of pyridyl nitrogen and carbonyl oxygen atoms). In compound 2, each CuII ion is connected by HBTC to construct 2D polymeric layers, which are further linked into a novel 3,5-connected 3D coordination polymeric framework with (4·62)(4·66·83) topology by 3-bpfp ligand in μ2-bridging mode (via ligation of pyridyl nitrogen atoms). Compound 2 is the first 3D example of coordination polymer constructed from 3-bpfp and aromatic polycarboxylate ligands. Moreover, the electrochemical properties of the three copper compounds bulk modified carbon paste electrodes have been studied.