Wave-like Network Research Articles

Synthesis, Structure and Thermal Properties of Two New Nickel(II) Coordination Polymers Based on Diphenic Acid and Bis(Imidazole) Ligands

Two novel nickel(II) coordination polymers, Ni(DPA)(BIX) (1) and Ni2(DPA)2(FBIX)2·H2O (2) (H2DPA = diphenic acid, BIX = 1,4-bis(imidazol-1-ylmethyl)benzene and FBIX = 2,3,5,6-tetrafluoro-1,4-bis(imidazol-1-ylmethyl)benzene), have been synthesized under the hydrothermal conditions and characterized by IR, elemental analysis and single crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 35.504(4) A, b = 7.6014(9) A, c = 19.894(2) A, β = 121.607(2)°, V = 4,572.6(9) A3, Z = 8, R 1 = 0.0461 and wR 2 = 0.1193. Complex 2 crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 21.623(2) A, b = 13.9245(15) A, c = 19.743(3) A, β = 119.2360(10)°, V = 5,187.2(12) A3, Z = 4, R 1 = 0.0399 and wR 2 = 0.1034. Complex 1 affords a two-dimensional (2D) wave-like layer network based on the intersection of Ni-BIX and Ni-DPA chains, while complex 2 is an interesting three-dimensional (3D) 4-connected network with a point symbol of (65.8). A careful structural comparison reveals the similarity of the Ni(II) coordination geometry and ligand binding mode. The significant discrepancy of their network structures may be attributed to the fluorinated substituent group. Two novel nickel(II) coordination polymers have been synthesized under the hydrothermal conditions. Complex 1 affords a two-dimensional (2D) wave-like layer network based on the intersection of Ni-BIX and Ni-DPA chains, while complex 2 is an interesting three-dimensional (3D) 4-connected network with (65.8) topology. The results show that the substituent group plays a significant role in the assembly process.

Ligand-controlled assembly of cobalt(II) metal–organic complexes from different semirigid bis(imidazole) derivatives and aromatic monocarboxylates: Electrochemical behaviors and fluorescent properties

To explore the influence of the conformation and substitute group of organic ligands on constructing coordination polymers, we synthesized four Co(II) metal–organic complexes, namely, [Co(bix)(BBA)2]2 (1), [Co(bix)(DNBA)2] (2), [Co(dmpbbbm)(BBA)2] (3) and [Co(dmpbbbm)(DNBA)(Cl)] (4) (bix=1,4-bis(imidazol-1-ylmethyl)benzene, dmpbbbm=1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, HBBA=4-bromobenzoic acid, HDNBA=3,5-dinitrobenzoic acid) under hydrothermal conditions. Complex 1 is a dinuclear cluster and is finally extended into a one-dimensional (1D) supramolecular chain though H-bonding interactions. Complex 2 shows 1D right-handed helical chains. Complex 3 possesses meso-helical chains with left- and right-handed helix, which is further extended into a two-dimensional (2D) supramolecular wave-like network through π–π stacking interactions. Complex 4 exhibits a meso-helical chain with left- and right-handed helical loops in one single strand, which is ultimately packed into a three-dimensional (3D) supramolecular framework through π–π stacking interactions. In addition, the thermal stability, the fluorescent properties and the electrochemical behaviors of the title complexes at room temperature have been investigated.

Bis(7-amino-1,2,4-triazolo[1,5-a]pyrimidin-4-ium) bis-(oxalato-κO,O)cuprate(II) dihydrate.

The structure of the title ionic compound, (C5H6N5)2[Cu(C2O4)2]·2H2O, consists of a centrosymmetric copper(II) oxalate dianion, two monoprotonated mol­ecules of the adenine analog 7-amino-1,2,4-triazolo[1,5-a]pyrimidine (7atp) and two water mol­ecules of crystallization. The CuII ion, located on an inversion center, exhibits a sligthly distorted square-planar coordination geometry, in which two oxalate anions bind in a bidentate fashion. The triazolopyrimidine ligand is protonated at the N atom in position 4, instead of its most basic N atom in position 3. This fact may be explained by the network stability, which is provided through the formation of a two-dimensional wave-like network parallel to (50) by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds. These nets are further connected via C—H⋯O inter­actions.

3-Amino-benzonitrile-3,5-dinitro-benzoic acid (1/1).

The asymmetric unit of the title co-crystal, C7H6N2·C7H4N2O6, contains two formula units of both components. The crystal structure is stabilized by inter­molecular O—H⋯O, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds, generating a two-dimensional wave-like network. π–π stacking inter­actions [centroid–centroid distances = 3.702 (2), 3.660 (2)and 3.671 (2) Å] stabilize the crystal packing.

Synthesis, structure, and properties of a coordination polymer based on N- and O-donors

A ternary coordination polymer, [Cd(L)(pbda)0.5] n [HL = 3,5-bis(2-pyridylmethyl)aminobenzoic acid, pbda = dianion of 1,4-benzenedicarboxylic acid], has been synthesized and characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction, thermogravimetric analysis, and single-crystal X-ray diffraction analysis. The single-crystal X-ray crystallography reveals that the complex is a 2-D wave-like network. The cadmium has an unsymmetrical seven-coordinate [CdN2O5] geometry, coordinated by two nitrogens and five oxygens from L− and pbda. Hydrogen bonds between the uncoordinated (2-pyridylmethyl)amino groups from adjacent layers form dimers across the inversion center, superposing different layers to construct a 3-D framework. To the best of our knowledge, [Cd(L)(pbda)0.5] n represents the first example of a complex containing 3,5-bis(2-pyridylmethyl)aminobenzoate.

Design and syntheses of two threefold interpenetrating 2-D networks

Two new interpenetrating networks, [Ni(2,2′-bpy)(5-npa)(bpe)0.5(H2O)] n (1) and [Ni(2,2′-bpy)(5-npa)(bpa)0.5(H2O)] n (2) (2,2′-bpy = 2,2′-bipyridine, 5-npa = 5-nitroisophthalato, bpe = 1,2-bis(4-pyridyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethane), have been synthesized and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, X-ray powder diffraction, and single-crystal X-ray diffraction. Complexes 1 and 2 have similar structures and show a threefold interpenetrating topology constructed by three 2-D wave-like networks. Secondary building unit (SBU), [Ni(2,2′-bpy)(5-npa)(H2O)] n , was used as starting material of the multistep reaction. Replacing one coordination bond of chelating carboxyl group of SBUs by bpe and bpa afford the two threefold interpenetrating complexes.

Keggin 型硼钨酸与1,4-二(1H-吡唑甲基)苯及铜有机-无机杂化物的二维网状结构与性质

An organic-inorganic hybrid compound [Cu4L5(HL)][BW12O40] {L=1,4-bis((1H-pyrazol-1-yl)methyl)benzene} was produced by hydrothermally synthesis from Keggin-type borotungstate, L, and Cu(NO3)2. The hybrid compound displayed a novel wavelike 2D network formed by shared edges of a core unit composed of ten Cu in a cyclic arrangement. Cyclic voltammetry showed that the reduction process was surface and diffusion controlled.

From ladder, net to framework: Coordination polymers based on Zn(ii)/Cd(ii) ions and mixed bicarboxyl- and bipyridine-containing linear ligands

The simultaneous use of bicarboxylate- and bipyridine-containing linear ligands to react with d10 metals affords four new polymeric compounds, [Zn(cis-chdc)(bpp)]·6H2O (1), [Zn(cis-chdc)(bpmp)] (2), [Cd2(cis-chdc)2(bpmp)(H2O)2] (3) and [Cd3(tp)3(bpp)2]•2DMF•6H2O (4) (H2chdc = 1,4-cyclohexanedicarboxylic acid; bpp = 1,3-bis(4-pyridyl)propane; bpmp = N,N′-bis(4-pyridylmethyl)piperazine; H2tp = terephthalic acid), which have been structurally characterized by elemental analysis, IR, TG, powder X-ray diffraction and single-crystal X-ray diffraction. Compound 1 possesses a 1-D ladderlike structural feature, compounds 2 and 3 show two different 2-D wavelike networks with the same (4•4) network topology, and compound 4 exhibits a 3-D open framework with (424•64) framework topology (similar to the CsCl-type body-centered cubic lattice). The structural features and the dimension evolution of the four compounds, along with the influence of nodes and mixed linear ligands are presented and discussed. The fluorescent properties of the four compounds are also investigated.

Unprecedented cyclic [Mo6O19]2−cluster and five organic–inorganic hybrids based on polyoxomolybdates and 4-amino-3,5-bis(pyridyl)-1,2,4-triazole

Five novel hybrid compounds, [Mo8O26Cu2(4-abpt)2]n·4nH2O (1), (4-H2abpt)2[Mo8O26] (2), [Mo8O26Cu2(3-abpt)2(H2O)2]n (3), [MoO4Cu(3-abpt)(H2O)]n (4), and [Mo6O19Co(3-abpt)2]n·4nH2O (5) were prepared by reacting MoO3/(NH4)6Mo7O24 with 4-amino-3,5-bis(3/4-pyridyl)-1,2,4-triazole (3/4-abpt) and corresponding metal salts. Compound 1 is a 2D coordination polymer containing extended γ-[Mo8O26]4− and [Cu2(4-abpt)2]4+ ribbons. Compound 2 is a supramolecular hybrid aggregate composed of H-bond linking β-[Mo8O26]4− and 4-H2abpt2+. Compound 3 exhibits a 2D rectangular network constructed by isolated β-[Mo8O26]4−clusters and [Cu2(3-abpt)2]4+. In compound 4, each MoO42− anion links two Cu(II) ions to form a S-type [CuMoO4]n chain, which is further linked by bidentate 3-abpt to form a 2D wave-like network. In complex 5, unprecedented cyclic [Mo6O19]2−cluster links two neighbouring hexamolybdates and two Co(II) ions to form a 2D [CoMo6O19]n network, which is further pillared by tetradentate 3-abpt to generate a 3D metal–organic framework. These compounds are thermally stable under 250 °C. The composites of the final residues were analyzed by PXRD.

5,11,17,23‐Tetrakis[( p ‐carboxyphenyl)azo]‐25,26,27,28‐tetrahydroxy Calix[4]arene: Crystal Structure and pH Sensing Properties

Treatment of 5,11,17,23-tetrakis[(p-carboxyphenyl)azo]-25,26,27,28-tetrahydroxy calix[4]arene (2) with HCl in DMF or NaOH in MeOH produced 5,11,17,23-tetrakis[(p-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]-arene·4DMF (2·4DMF) and 5,11,17,23-tetrakis[(p-carboxyphenylsodium)azo]-25,26,27,28-tetrahydroxycalix[4]- arene (3), respectively, which were characterized by elemental analysis, IR, UV-vis, 1H NMR and 13C NMR. An X-ray analysis of 2·4DMF revealed that its calix[4]arene core adopts a flattened cone conformation in which opposed phenyl groups take parallel or sharply inclined positions. The intra- and intermolecular hydrogen-bonding interactions and the π···π interactions form a 2D hydrogen-bonded wavelike network. Compound 2 had a unique reversible color change in a wide pH range from 1 to 13.5 and showed interesting pH sensing properties.

Hydro(solvo)thermal synthesis and structural characterization of three lanthanide–carboxylate coordination polymers based on BDC and/or EDTA

Three lanthanide coordination polymers, [Ln4(BDC)6(H2O)2] n (Ln = Er, 1; Ln = Tm, 2; BDC = 1,2-benzenedicarboxylate) and {[Nd2(BDC)(EDTA)(H2O)2] · 1.5H2O} n , 3, were prepared by hydrothermal synthesis and characterized by elemental analysis, IR spectra, as well as single-crystal X-ray diffraction. The isostructural coordination polymers 1 and 2 exhibit four different coordination modes, which are rarely found in one lanthanide complex. Complex 3 displays a 2-D wave-like network assembled by two polycarboxylate ligands.

Structure modulation of metal–organic frameworks via reaction pH: Self-assembly of a new carboxylate containing ligand N-(3-carboxyphenyl)iminodiacetic acid with cadmium(II) and cobalt(II) salts

Self-assembly of a new carboxylate containing ligand, N-(3-carboxyphenyl)iminodiacetic acid (H 3L), with Cd(II) and Co(II) salts under different reaction pH results in the formation of four new coordination polymers, namely [Cd(HL)(H 2O)] ( 1), [Co(HL)(H 2O)] ( 2), [Cd(HL)(H 2O) 4] ( 3) and [Cd 3(L) 2(H 2O) 9] · 7H 2O ( 4). Single crystal X-ray diffraction analysis indicates that 1 and 2 are isomorphous and isostructural with a 2D wave-like network structure, while 3 has a 1D zigzag chain structure. The complexes 1– 3 were obtained at low pH (<7) which makes the ligands only partly deprotonated. However, complex 4, obtained at pH 7 with all the carboxylate groups deprotonated, exhibits a 2D network structure. The results suggest that the reaction pH is one of the key factors in the formation of the coordination architectures. In addition, the photoluminescence properties of the free ligand (H 3L) and complexes 1, 3 and 4 were studied in the solid state at room temperature. Moreover, the magnetic property of complex 2 was investigated.

Three copper(II) complexes constructed from a new 1,3,5-triazine derivative ligand

Three new complexes {[Cu(dpdapt)(Hhbd)] · 6H 2O} n ( 1) (dpdapt = N, N′-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine, Hhbd = 2-hydroxybutanedioicate dianion), [Cu(dpdapt)(SO 4)] · 2H 2O ( 2) and [Cu(dpdapt)(oxa)] · H 2O ( 3) (oxa = oxalate dianion) have been synthesized and structurally characterized. The non-covalent interactions of π–π stacking and hydrogen bonding extend complexes 1– 3 into supramolecular architectures, where 1 self-assembles into a 1D polymeric chain by dicarboxylate bridges and exhibits a 3D framework with 1D open channels, while complexes 2 and 3 display 2D wavelike networks. Interestingly, in 1, the host framework encapsulates hexameric water clusters that are connected into 1D arrays by supramolecular association along the 1D open channels. The UV/vis, IR spectra, fluorescence and TG analysis for complexes 1, 2 and 3 are also discussed.

Synthesis, structure and magnetic studies of two-dimensional network of Cu(II) polymer using malonate and 4,4′-azobispyridine ligands

The malonato-bridged copper(II) complex [Cu(mal)(H 2O)(azpy) 1/2] · H 2O ( 1) (mal = malonate, azpy = 4,4′-azobispyridine) has been synthesized and characterized by X-ray diffraction. The structure of 1 consists of malonato-bridged uniform copper(II) chains which are covalent connected through azpy to form two-dimensional wavelike network. The magnetic pathway of complex 1 is through a single syn– anti carboxylate bridge connecting equatorial and equatorial positions of adjacent copper(II) atoms, and have the value of the intrachain ferromagnetic coupling ( J = 8.73(3) cm −1) and interchain antiferromagnetic coupling ( zJ′ = − 1.31(1) cm −1) through a numerical expression for a ferromagnetic uniform chain.

Homochiral helical wavelike (4,4) networks constructed by divalent metal ions and S-carboxymethyl- l-cysteine

The synthesis, X-ray characterization and second-harmonic generation of three new two-dimensional coordination polymers [CuL(H 2O)] n ( 1), [ZnL(H 2O)] n ( 2) and {[CdL(H 2O)]·2H 2O} n ( 3) (L= S-carboxymethyl- l-cysteine) are reported, which exhibit wavelike (4,4) topology, and are assembled into three-dimensional networks by hydrogen-bonding interactions. The most intriguing feature in 1, 2 and 3 is the presence of two types of homo-chiral helices. They crystallize in the chiral space groups P2 1 or P2 12 12 1, and displays modest powder SHG efficiencies.

Neuronal Avalanches in Neocortical Circuits

Networks of living neurons exhibit diverse patterns of activity, including oscillations, synchrony, and waves. Recent work in physics has shown yet another mode of activity in systems composed of many nonlinear units interacting locally. For example, avalanches, earthquakes, and forest fires all propagate in systems organized into a critical state in which event sizes show no characteristic scale and are described by power laws. We hypothesized that a similar mode of activity with complex emergent properties could exist in networks of cortical neurons. We investigated this issue in mature organotypic cultures and acute slices of rat cortex by recording spontaneous local field potentials continuously using a 60 channel multielectrode array. Here, we show that propagation of spontaneous activity in cortical networks is described by equations that govern avalanches. As predicted by theory for a critical branching process, the propagation obeys a power law with an exponent of -3/2 for event sizes, with a branching parameter close to the critical value of 1. Simulations show that a branching parameter at this value optimizes information transmission in feedforward networks, while preventing runaway network excitation. Our findings suggest that "neuronal avalanches" may be a generic property of cortical networks, and represent a mode of activity that differs profoundly from oscillatory, synchronized, or wave-like network states. In the critical state, the network may satisfy the competing demands of information transmission and network stability.

Syntheses and crystal structures of four metal–organic co-ordination networks constructed from cadmium(II) thiocyanate and nicotinic acid derivatives with hydrogen bonds

Four novel non-interpenetrating metal–organic co-ordination networks of the CdII–L–NCS− system have been prepared using potentially bridging nicotinic acid derivatives L [nicotinic acid (HL1), nicotinamide (L2), isonicotinamide (L3), or isonicotinate (L4)]. Their crystal structures were determined by X-ray diffraction. In [Cd(SCN)2(HL1)2]·HL11 each pair of cadmium(II) ions is bridged by two inversely related μ-NCS−-N,S ligands to form infinite chains with the remaining two trans positions of six-co-ordinated Cd atoms being occupied by two HL1 ligands, which form head-to-head double hydrogen bonds using the unco-ordinated carboxyl groups between adjacent chains to form two-dimensional layers. Weak S ⋯ S interactions between the NCS− ligands extend the layers into a three-dimensional framework with the channels enclosing HL1 guest molecules, which are interlinked into chains through O–H ⋯ N hydrogen bonds. [Cd(SCN)2(L2)2]·H2O 2 and [Cd(SCN)2(L3)2] 3 are interesting in that they contain unprecedented 16-membered [Cd4(μ-SCN-N,S)4] rings in the two-dimensional sheets. Between the sheets N–H ⋯ O amide–amide hydrogen bonds extend the two-dimensional layers to three-dimensional structures. [Cd(SCN)(L4)(H2O)] 4 exhibits two-dimensional wave-like networks with bridging NCS− and L4 ligands using both ends in co-ordination. The results demonstrate that the structures of the CdII–L–NCS system deeply depend on the nature of the nicotinic acid derivatives L.