Qi-Zhen Shi

A series of Zn(II) coordination complexes derived from isomeric phenylenediacetic acid and dipyridyl ligands: syntheses, crystal structures, and characterizations

A series of new metal–organic frameworks (MOFs), [Zn(1,2-pda)(bipy)(H2O)2]n (1), [Zn(1,3-pda) (bipy)(H2O)]n·nH2O (2), [Zn(1,4-pda)(bipy)]n·nCH3OH (3), [Zn(1,2-pda)(dpe)]n·3nH2O (4), and [Zn(1,3-pda)(bpa)]n·2nH2O (5) [H2pda = phenylenediacetic acid, bipy = 4,4′-bipyridine, dpe = 1,2-di(4-pyridyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethane] have been synthesized and structurally characterized. The structure determination reveals that complex 1 is a 2D layered network and exhibits a typical (4,4) topological net, which further assembles into a 3D two-fold interpenetrated pcu topology when hydrogen bonding interactions are considered. Complex 2 shows a 2D (5,2)-connected topological network via hydrogen bonding interactions based on the 1D double-chains. For complex 3, when the 1,4-pda ligands act as a three-connected node, the 2D double-layered structure displays a unique (5,3)-connected topology with a Schlafli symbol (42,67,8)(42,6). Complex 4 features a rare 3D three-fold interpenetrated diamondoid framework (dia, 66 topology) with (2.2.1) Hopf links and (6.3.3) Torus links, and the helical water chains are encased in the 1D neighboring channels. Complex 5 is a 2D corrugated net with a Schlafli symbol (44,62), and the puckered nature of the layers assembles them to interpenetrate in an unusual 2D → 3D parallel fashion. Particularly, a discrete tetramer water cluster, (H2O)4, is located in the crystal lattice of 5. The structural differences demonstrate that the backbones of the phenylenediacetic acids are a key point to form the final metal–ligand coordination polymers. Moreover, the fluorescent properties of complexes 1–5 were studied in the solid state at room temperature.

Trinuclear-based Copper(I) Pyrazolate Polymers: Effect of Trimer π-Acid···Halide/Pseudohalide Interactions on the Supramolecular Structure and Phosphorescence

Under different situations, solvothermal reactions of 3,5-diethyl-4-(4-pyridyl)-pyrazole (HL) with CuX or CuX(2) (X = Cl, Br, I, and SCN) afforded five copper(I) coordination polymers, {CuX[CuL](3)·solvent}(n) (X = Cl, 1; Br, 2; I, 3; X = SCN and solvent = MeCN, 4) and {Cu(2)I(2)[CuL](3)}(n) (5). X-ray diffraction analyses show that all the complexes have trinuclear [CuL](3) (referred as Cu(3)) secondary building units featuring planar nine-membered Cu(3)N(6) metallocycles with three peripheral pyridyl groups as connectors, which are further linked by CuX or Cu(2)X(2) motifs to generate single- or double-strand chains. Interestingly, the Cu(I) atoms within the Cu(3) units in 1-5 behave as coordinatively unsaturated π-acid centers to contact soft halide/pseudohalide X atoms of CuX and Cu(2)X(2) motifs, which lead to novel sandwich substructures of [(Cu(3))(Cu(2)X(2))(Cu(3))] (X = Br, I, and SCN) in 2-4. In addition, both the π-acid [Cu(3)]···X contacts and intertrimer Cu···Cu interactions contribute to the one-dimensional (1D) double-strand and 2D/3D supramolecular structures of 1-5. All of these complexes exhibit high thermostability and bright solid-state phosphorescence upon exposure to UV radiation at room temperature. The emissions arise from the mixtures of metal-centered charge transfer, metal to ligand charge transfer, and halide-to-ligand charge transfer excited states, and can be tuned by intermolecular π-acid [Cu(3)]···halide/pseudohalide contacts.

A series of intriguing metal–organic frameworks with 3,3′,4,4′- benzophenonetetracarboxylic acid: structural adjustment and pH-dependence

To understand the influence of the pH parameter on crystal growth, six compounds prepared at different pH values have been explored, namely {Cu(H2bptc)(bpa)(μ2-H2O)}n (1) {[Cu3(Hbptc)2(bpa)3(H2O)8]·4H2O}n (2), {[Cu2(bptc)(bpa)2(H2O)]·6.5H2O}n (3), {[Mn2(bptc)(bpa) (μ2-H2O)(H2O)5]·H2O}n (4), {[Co2(bptc)(bpe)(μ2-H2O)(H2O)5]·H2O}n (5) and {[Mn2(bptc)(bpe) (μ2-H2O)(H2O)5]·H2O}n (6) (H4bptc = 3,3′,4,4′- benzophenonetetracarboxylic acid, bpa = 1,2-bis(4-pyridy)ethane and bpe = 1,2-bis(4-pyridy)ethene). The structure of 1 displays a 3D open rhombic framework based on an infinite metal-aqua chain. Compound 2 contains two different motifs: a cationic 1D chain of [Cu(bpa)(H2O)4]2+, and an anionic 2D network of [Cu2(Hbptc)2(bpa)2(H2O)4]2−. Compound 3, a microporous open-framework structure, presents an uncommon 3D, trinodal, 4-connected self-penetrating network. Compounds 4, 5 and 6 present the same arrangement with 4,6-connected 3D networks. Comparing the experimental results, it is clear that the pH value plays a crucial role in the formation of the resulting structures. The thermal stabilities of compounds 1–6 are discussed. The magnetic properties for 2 and 4 are also studied and they both exhibit a weak antiferromagnetic coupling through the O2C–C–C–CO2 bridge and μ2-aqua bridge, respectively.

Self-assembled coordination polymers of V-shaped bis(pyridyl)thiadiazole dependent upon the spacer length and flexibility of aliphatic dicarboxylate ligands

An investigation into 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and cupric or cadmium complexes with a large variety of aliphatic α,ω-dicarboxylic acids HOOC-X-COOH (X = (CH2)n, n = 0–4 corresponding to oxalic acid (H2ox), malonic acid (H2mal), succinic acid (H2suc), glutaric acid (H2glu) and adipic acid (H2adi); CHCH, maleic acid (H2male) and fumaric acid (H2fum)) is performed. Ten novel metal–organic architectures, [Cu2(bpt)(ox)2]n·2.92nH2O (1), [Cu(bpt)(mal)(H2O)]n·2nH2O (2), [Cu(bpt)(glu)]n (3), [Cu(bpt)(adi)]n (4), [Cu2(bpt)2(fum)2]n·3nH2O (5), [Cd(bpt)(mal)(H2O)]n (6), [Cd(bpt)(suc)]n (7), [Cd(bpt)(glu)]n·nH2O (8), [Cd2(bpt)2(male)2]n·2nH2O (9), and [Cd(bpt)(fum)(H2O)]n·nH2O (10) were successfully synthesized through varying the organic acid linkers. The molecule 1 is a 3D pillared-layer framework with the open channels encapsulating infinite 1D water chains. Complex 2 shows the contorted 2D layer, which is extended to a 2-fold interpenetrated 3D supramolecular net by antidromic R24(8) hydrogen-bonding pattern. Compound 3 is a grid-like layer motif with the terminal bpt ligands as pendants. The MOFs 4 and 5 present two-fold interpenetrating primitive cubic (α-Po) coordination networks. Interestingly, discrete tetrameric water clusters exist in the micropores of the MOF 5. For the cadmium complex 6, six-coordinated metal centers link malonate and bpt to form interdigitated layers through edge-to-face π–π stacking interactions. Coordination polymer 7 can be considered as six-connected self-penetrated topological 3D network, in which the right- and left-handed helices are alternately arranged into a wavy Cd/succinate layer. Flexible glutarate with cadmium atoms produces a 1D ribbon, and is further linked by bpt ligands to produce the 2D double-layered motif 8. Incorporating with rigid butenedioic acid, the reaction of seven-coordinated cadmium and bpt leads to two distinct 2D (4,4) layered frameworks 9 and 10, with a one-dimensional Cd–O chain observed in the former framework. A systematic structural comparison of these ten complexes indicates that the final polymeric structures could be tuned through the introduction of the different backbone length and flexibility of the aliphatic dicarboxylates. In addition, host–guest chemistry of MOFs 1 and 5, and the luminescent properties of cadmium compounds were discussed.

Generation of a 4-crossing [2]-catenane motif by the 2D→2D parallel interpenetration of pairs of (4,4) sheets

A fascinating new series of structures in which 4-crossing [2]-catenane motifs are formed between pairs of interpenetrating 2D sheets; moreover, the inclined orientation of the two interpenetrating nets with a layer leads to the wrapping of helical chains of one net around zigzag chains of the other.

Solvents influence on sizes of channels in three fry topological Mn(II)-MOFs based on metal–carboxylate chains: syntheses, structures and magnetic properties

Three new 3D Mn(II)-MOFs have been synthesized via solvothermal reaction with MnCl2·4H2O and [1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylic acid (H4tptc) in three different solvents [N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF)], namely, [Mn2(tptc)(H2O)(NMP)]·NMP (1), [Mn2(tptc)(H2O)(DMA)]·DMA (2) and Mn2(tptc)(DMF)2 (3), all of which were fully characterized. In 1 and 2, the 1D uniform Mn–carboxylate chains with the (μ-EO-H2O/NMP/DMA)(μ-COO)2 triple bridges (EO = end-on) are extended by the tptc linkers to form a 3D (3,4)-connected fry net with 1D irregular quadrangular channels. Interestingly, 3 possess two kinds of Mn–carboxylate chains and can also be simplified as a fry net. The self-assembly synthesis system responds to small carbonyl solvents (NMP, DMA and DMF) with very high sensitivity and selectivity, but products using hydroxy solvents (methanol, alcohol and isopropanol) were not identified. The various pore frameworks of 1–3 are filled by different coordinated and latticed solvent molecules in their channels. The sizes of the channels [3 (33.11 A2) < 2 (35.17 A2) < 1 (35.37 A2)] are induced by the sizes of the solvent molecules (DMF < DMA < NMP). The good chemical stabilities of 1–3 were observed. Magnetic studies demonstrate that the magnetic coupling through the mixed carboxylate bridges in all compounds is antiferromagnetic.

An Unusual 3D Entangled Co(II) Coordination Polymer Directed by Ferromagnetic Molecular Building Block

A fascinating 3D entangled metal-organic framework, namely, {[Co(2)(bcp)(2)]·3H(2)O}(n) (1), was obtained through the solvothermal generation of flexible and long dicarboxylate (bcp) and metal salt. The crystal structure contains a 1D metal chain with bcp ligands wrapped around it in a wavy line and features an unusual entangled topological net. Furthermore, the magnetic behavior of 1 was also studied and indicated the existence of ferromagnetic interaction and long-range ordering character.

Syntheses, characterization and crystal structure of copper(II) α,β-unsaturated carboxylate complexes with imidazole

Abstract Four copper(II) α,β-unsaturated carboxylate complexes with imidazole, Cu(CH2=CH–COO)2(imH)2 (1), Cu2(CH2=CH–COO)4(imH)2 (2), Cu[CH2=C(CH3)–COO]2(imH)2 (3) and Cu2[CH2=C(CH3)–COO]4(imH)2 (4) (where imH=imidazole) have been prepared and characterized by elemental analyses, IR, ESR and electronic reflectance spectroscopies. The single crystal X-ray diffraction study of complex 3 shows that the copper(II) atom is in a symmetric centre of a square planar environment completed by two monodentate α-methacrylate groups and two imidazole ligands displayed in trans position. Each molecular unit is linked with four neighbouring units by hydrogen-bond interactions forming a two-dimensional supramolecular compound (dN⋯O=2.781 A). Complex 1 has a similar structure as complex 3, while complexes 2 and 4 have a binuclear cage structure. The ESR spectra show that the spin coupling between the unpaired electrons of Cu(II) atoms present in complexes 2 and 4, is not observed in complexes 1 and 3. The electronic reflectance spectra suggest that the d–d transitions of complexes 1 and 3 are in a square planar ligand field, while that of complexes 2 and 4 are in a tetragonal ligand field, and the ligand field strength of acrylate group and α-methacrylate group is similar. Complexes 1 and 2 as well as 3 and 4, were produced simultaneously in the reaction of the corresponding copper(II) α,β-unsaturated carboxylate with imidazole in methanol solution.

A novel polythreaded metal–organic framework with inherent features of different side arms and five-fold interpenetration

Self-assembly led to a fascinating type of 2D → 3D polythreaded architecture with different side arms involving nine polymeric units at a time, which exhibits the highest threaded degree presently known for 2D motifs. Especially, when hydrogen bonds are taken into account, the resulting structure displays topologically a 5-fold interpenetrated 3D mot framework.

An unusual 1D ladder-like silver(I) coordination polymer involving novel 1D → 3D five-folded interpenetrated and [3 + 2] catenaned features generated by Ag⋯O interactions

An unusual 1D ladder-like silver(I) complex has been synthesized and characterized. The polymer exhibits interesting plywood-like stacking arrays and a novel five-folded interpenetrated supramolecular network with [3 + 2] catenations.