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The influence of synthesis temperature and time on the length (capacity) of the plateau region during first charge in the high-capacity lithium-rich layered oxide Li1.2Mn0.6Ni0.2O2 and on the reversible capacity during subsequent charge–discharge cycles has been systematically investigated. The samples were synthesized by firing a sol–gel precursor obtained at 450 °C at various temperatures (850–1000 °C) for 24 h and at the optimum temperature of 900 °C for 6–72 h. The maximum length of the plateau region during the first charge and, consequently the maximum reversible capacity were achieved with the sample fired at 900 °C for 24 h. In contrast, the sample fired at 1000 °C for 24 h does not show any plateau region. In-depth characterization by X-ray diffraction, aberration-corrected transmission electron microscopy, scanning electron microscopy, inductively coupled plasma analysis, and electrochemical charge–discharge measurements reveals that the actual lithium content in the synthesized samples, composi...

A chiral nickel histidine compound, [Ni(L-his)2]×H2O (1, L-his = anion of L-histidine), was synthesized in high yield from the reaction of Ni(OAc)2×4H2O and L-histidine in the presence of 4,4′-bipyridine under mild reaction conditions. A single-crystal X-ray diffraction analysis showed that compound 1 crystallizes in the monoclinic system, space group C2, with a chemical formula of C12H18N6NiO5, cell parameters: a = 29.416(2) A, b = 8.2667(7) A, c = 6.3137(5) A, β = 90.066(2)°, V = 1535.3(2) A3 and Z = 4. Each nickel(II) ion in 1 is six coordinated, bonded to two oxygen donors and four nitrogen donors from two crystallographically independent L-his− ligands with a tridentate coordination mode to form a monomeric species. Monomeric forms of 1 undergo self-assembly to form a three-dimensional (3D) supramolecular architecture via subtle combinations of N-H···O type hydrogen bonding interactions among the adjacent L-his−ligands and π-π stacking interactions among the imidazole rings of the L-his− ligands. The supramolecular entity exhibits an unusually high thermal stability, at temperatures of up to 360 °C and shows reversible de-/re-hydration properties.

Electron density distribution of 2,2′-dipyridylamine (Hdpa) is studied by single-crystal X-ray diffraction method at 120 K. Structural determination reveals that the conformation of Hdpa molecule is the syn-anti conformation caused by the intramolecular N···H-C hydrogen bond between two pyridine rings. Two Hdpa molecules flock together via two intermolecular N···H-N hydrogen bonds to form a dimer. Bond characterization is made in terms of deformation density (Δρ), topological analysis of total electron density based on multipole model and molecular orbital (DFT) calculation. The agreement between experiment and theory is good. The topological properties of bond critical points at C-C, C-N, N-H and C-H bonds are reasonable and reveal a covalent bond character with the high ρ(rc), negative ∇2ρ(rc) and negative total energy density H((rc) values. A low ρ(rc) and positive ∇2ρ(rc) of bond critical points at N···H bonds reveal a closed-shell interaction for C-H···N and N-H···N hydrogen bonds. The π-delocalization feature around the pyridine ring is also performed by bond ellipticity (ϵ) and fermi-hole distribution.

A new polymeric complex, [Fe(bpno)2(NCS)3]n (1) (bpno = 4,4′-bipyridyl-N,N′-dioxide) have been synhesized and structural characterized by single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system, space group P-1, with chemical formula C23H16FeN7O4S3, a = 9.0738(5), b = 9.7175(5), c = 15.0329(8) A, α = 97.668(1), β = 92.581(1) and γ = 102.441(1)°, V = 1279.1(1) and Z = 2. Structural determination reveals that the coordination environment of the iron(III) ion is distorted octahedral, bonded with three oxygen donors of three bpno and three nitrogen donors of three NCS− ligands. The bpno ligands adopt two different coodination modes, a monodentate coordination mode and a bis-monodentate coordination mode, which links the Fe(III) ions to form a one-dimensional (1D) zigzag chain-like coordination polymer. Neighbouring chains are mutually connected via the C-H···O type hydrogen bonds to form a 2D hydrogen-bonded layered framework and then extended to a 3D supramolecular architecture via π-π interaction between the pyridyl rings of bpno ligands and unconventional C-H···S hydrogen bonding interactions. Compound 1 exhibits moderate thermo-stability and keeps its crystalline forms up to 190 °C.

TiO2 with different morphology was deposited on acid-treated multi-walled carbon nanotubes (CNTs) by atomic layer deposition at 100 °C-300 °C to form a TiO2@CNT structure. The TiO2 fabricated at 100 °C was an amorphous film, but became crystalline anatase nanoparticles when fabricated at 200 °C and 300 °C. The saturation growth rates of TiO2 nanoparticles at 300 °C were about 1.5 and 0.4 A/cycle for substrate-enhanced growth and linear growth processes, respectively. It was found that the rate constants for methylene blue degradation by the TiO2@CNT structure formed at 300 °C were more suitable to fit with second-order reaction. The size of 9 nm exhibited the best degradation efficiency, because of the high specific area and appropriate diffusion length for the electrons and holes.

The effects of hydrogen thermal and plasma treatment on the formation and photocatalytic activities of black TiO2 nanowire arrays were investigated and discussed. After either the hydrogen thermal or plasma treatment, the TiO2 nanowires remained. However, in contrast to the plasma treated nanowires, the diameter of the thermal treated TiO2 nanowires reduced more significantly, which was attributed to a thicker surface amorphous layer and more oxygen vacancies. A higher photoresponse in both UV and visible light regions and more hydroxide groups were also observed for the thermal treated nanowires. In addition, the black nanowires possessed greater carrier concentration, leading to a more efficient separation of electron-hole pairs. As a consequence, much enhanced photoelectrochemical water splitting and photocatalytic degradation of methylene blue were obtained.

In this highlight, we have focused our attention on several examples of coordination polymers (CPs) and metal–organic frameworks (MOFs) that exhibit water-induced reversible SCSC or solid-state structural transformations under thermal conditions. Dissociation or removal of coordinated or solvated water molecules and exposure to moisture in air may cause reversible SCSC or solid-state structural transformations, which are mainly demonstrated through single-crystal X-ray diffraction, powder X-ray diffraction and cyclic TG measurement and manifested by various physical properties, such as colour, magnetism, luminescence, etc., due to changes in coordination number and geometry, structural dimensionality, interpenetration, etc.

An efficient Integrated Bandwidth Allocation Scheme (IBAS) is proposed to serve the lower priority requests can be early assigned the bandwidth without waiting too long. These will speed up the channel capture by priority data to support the multimedia traffic over DOCSIS-compliant cable networks. The efficiency of IBAS is investigated by simulations. The results show that by adopting IBAS can not only shorten the collision period but also minimize the average request delay of lower priority requests. Performance has been improved in throughput and delay compares to the current DOCSIS specifications.

The integration of WiMAX networks and multi-protocol label switching (MPLS) networks, called WiMPLS networks, is the trend for nomadic Internet access in the fourth generation (4G) wireless networks. The base station (BS) in such heterogeneous networks will play the role of bridge and router between the IEEE 802.16 subscriber stations (SSs) and MPLS networks. However, there is no such integrated solution so far and the switching efficiency of the BS should be considered as well. This paper, therefore, adopts a cross-layer fashion (from network layer to MAC layer) to design the end-to-end label switching protocol (ELSP) for filling this gap. ELSP provides the mechanism of end-to-end (SS-to-SS) and layer 2 switching transfer for switching performance enhancement by assigning the SS with the MPLS labels (M-labels). The M-label can be carried by the IEEE 802.16e extended subheader within the MAC protocol data unit (MPDU), which is fully compliant with the IEEE 802.16e standard. The security issue caused by M-label usage is also concerned and solved in this paper. This paper also reveals an extra advantage that the switching delay of the BS achieved by ELSP can be as low as hardware-accelerated IP lookup mechanism, e.g., ternary content addressable memory (TCAM). Simulation results show that ELSP efficiently improves the end-to-end transfer delay as well as the throughput for WiMPLS heterogeneous networks.

Platinum nanoparticles as a catalyst for proton-exchange-membrane fuel cells (PEMFCs) were grown on nitric acid-treated multiwalled carbon nanotubes by atomic layer deposition (ALD) at 250 °C. Formation of uniform and well-distributed Pt nanoparticles was achieved. The size and number of Pt nanoparticles could be controlled by the ALD cycle number. The PEMFC test shows that for the membrane electrode assembly made of both anode- and cathode-deposited Pt (0.019 and 0.044 mg cm −2 , respectively) after 100 cycles of ALD has 11 times higher specific power density than that made of commercial E-Tek electrodes containing 0.5 mg cm −2 of Pt.

Three coordination polymers, {[Cd(3-bpd)2(NCS)2]×C2H5OH}n (1), {[Cd(3-bpd)(dpe)(NO3)2]×(3-bpd)}2 (2), {[Cd(dpe)2(NCS)2]×3-bpd×2H2O}n (3) (3-bpd = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene; dpe = 1,2-bis(4-pyridyl)ethane), were prepared and structurally characterized by a single-crystal X-ray diffraction method. In compound 1, each Cd(II) ion is six-coordinate bonded to six nitrogen atoms from four 3-bpd and two NCS− ligands. The 3-bpd acts as a bridging ligand connecting the Cd(II) ion to generate a 2D layered metal-organic framework (MOF) by using a rhomboidal-grid as the basic building units with the 44 topology. In compound 2, the Cd(II) ion is also six-coordinate bonded to four nitrogen atoms of two 3-bpd, two dpe and two oxygen atoms of two NO3− ligands. The 3-bpd and dpe ligands both adopt bis-monodentate coordination mode connecting the Cd(II) ions to generate a 2D layered MOF by using a rectangle-grid as the basic building units with the 44 topology. In compound 3, two crystallographically independent Cd(II) ions are both coordinated by four nitrogen atoms of dpe ligands in the basal plane and two nitrogen atom of NCS− in the axial sites. The dpe acts as a bridging ligand to connect the Cd(II) ions forming a 2D interpenetrating MOFs by using a square-grid as the basic unit with the 44 topology. All of their 2D layered MOFs in compounds 1-3 are then arranged in a parallel non-interpenetrating ABAB—packing manner in 1 and 2, and mutually interpenetrating manner in 3, respectively, to extend their 3D supramolecular architectures with their 1D pores intercalated with solvent (ethanol in 1 or H2O in 3) or free 3-bpd molecules in 2 and 3, respectively. The photoluminescence measurements of 1-3 reveal that the emission is tentatively assigned to originate from π-π* transition for 1 and 2 and probably due to ligand-center luminescence for compounds 3, respectively.

A potential bridging triazole-based ligand, atrz (trans-4,4'-azo-1,2,4-triazole), is chosen to serve as building sticks and incorporated with a spin crossover metal center to form a metal organic framework. Coordination polymers of iron(II) with the formula [Fe(μ-atrz)(3)]X(2)·2H(2)O (where X = ClO(4)(-) (1·2H(2)O) and BF(4)(-) (2·2H(2)O)) in a 3D framework and [Fe(μ-atrz)(μ-pyz)(NCS)(2)]·4H(2)O (3·4H(2)O) in a 2D layer structure were synthesized and structurally characterized. The magnetic measurements of 1·2H(2)O and 2·2H(2)O reveal spin transitions near room temperature; that of 3 exhibits an abrupt spin transition at ~200 K with a wide thermal hysteresis, and the spin transition behavior of these polymers are apparently correlated with the water content of the sample. Crystal structures have been determined both at high spin and at low spin states for 1·2H(2)O, 2·2H(2)O, and 3·4H(2)O. Each iron(II) center in 1·2H(2)O and 2·2H(2)O is octahedrally coordinated with six μ-atrz ligands, which in turn links the other Fe center forming a strong three-dimensional (3D) network; counteranion and water molecules are located in the voids of the lattice. The FeN(6) octahedron of 3·4H(2)O is formed with two atrz, two pyrazine (pyz) ligands, and two NCS(-) ligands, where the ligands atrz and pyz are bridged between iron centers forming a 2D layer polymer. A zigzag chain of water molecules is found between the layers, and there is a distinct correlation between the thermal hysteresis with the amount of water molecules the exist in the crystal.

A new coordination polymer, [Zn(dpe)(bdc)]·4H(2)O (ZndB; dpe=1,2-bis(4-pyridyl)ethane, bdc(2-)=dianion of benzenedicarboxylic acid), which possesses a 3D metal-organic framework (MOF) has been synthesized and structurally characterized. This 3D MOF is constructed by the assembly of helical channels filled with guest water molecules in both inner and outer regions of the channel. The resulting network also creates a 2D water layer containing hydrogen-bonded (H(2)O)(16) rings as the basic building units. Thermogravimetric and powder X-ray diffraction measurements of ZndB revealed a two-step weight loss of water molecules with a reversible water adsorption/desorption process in the inner channel for the first stage, and irreversible water desorption in the outer channel for the second stage. This spongelike property is manifested by the excimer emission originating from interaction between dpe (π*) and the other dpe (π) of the proximal helical channel, which is highly sensitive to the environmental perturbation. Powder X-ray analyses reveal that the dehydration process induces the readjustment of dpe π-π stacking distance/orientation, which results in dramatic luminescence changes from dim pale blue (λ(em)≈470 nm) upon hydration to bright white-light generation (broad, λ(em)≈500-550 nm) upon water depletion, accompanied by a ≈100-fold increase in the emission intensity.

Anodic aluminum oxide (AAO) film was used as a template to fabricate TiO2 nanotubes. TiO2 was deposited into the AAO pores by atomic layer deposition (ALD) at 100 °C. After the top layer of TiO2 and the AAO template were removed, an ordered array of TiO2 nanotubes remained on the substrate. The tube thickness increased with the cycle number of ALD. The UV–vis absorption spectra of the samples exhibited a red shift as the thickness increased or after annealing. The photocatalytic activity increased with the increase in the wall thickness of TiO2 nanotubes. With deposition of Ag nanoparticles on the tubes, the nanoparticles could act as an electron trapper to slow the electron–hole recombination rate, and thus enhance the efficiency of photodecomposition of methyl orange.

Coordination polymers of metal-croconate (C5O52−) complex, {[Ni2(bpe)2(C5O5)2]·H2O}n (1) (bpe = 1,2-bis(-4-pyridyl)ethylene)) with two-dimensional (2D) metal–organic frameworks (MOF), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1 contains two crystallographically independent Ni(II) ions which both lie in a distorted octahedral environment bonded to two bpe nitrogen atoms and four oxygen donors from two croconates. The croconate acts as a bridging ligand with two different bridging modes, one presents a bis-bidentate adjacent μ3-coordination mode and the other a bis-bidentate μ4-coordination mode. A 2D brick-wall-like layered framework is formed by using a rectangle grid as a basic building unit through the connectivity of NiII with hybrid μ3-, μ4-croconates and bpe ligands. Two layers are then cross-linked by the other bpe ligands to complete a 2D bi-layered MOF. The TGA associated with in situXRD measurements demonstrated that 1 have quite high thermo-stability that keep their crystalline forms up to 350 °C. Magnetic measurements show the long range magnetic ordering and spin canting behavior in 1 below the critical temperature of 22 K with an approximate canting angle of 0.79°. A large coercivity of 3.5 kOe in the hysteresis loop is observed at 1.8 K, indicating that 1 is a weak hard magnet.

A new coordination polymer, [Zn(HBTC)(BPE)0.5(H2O)]n·nH2O (1) with an extended 1D ladderlike metal-organic framework (MOF) has been synthesized and structural characterized by single-crystal X-ray diffraction method. Structural determination reveals that, in compound 1, the Zn(II) ion is four-coordinated in a distorted tetrahedral geometry, bonded to one nitrogen atom from one BPE ligand, and three oxygen atoms from two monodentate carboxylate groups of two HBTC(2-) ligands and one coordinated water molecule. The HBTC(2-) acts as a bridging ligand with a bis-monodentate coordination mode, connecting the Zn(II) ions to form a one-dimensional (1D) [Zn(HBTC)] chain. Two 1D chains are then interlinked via the connectivity between the Zn(II) ions and anti-BPE liagnds to complete the 1D ladderlike MOF. Adjacent 1D Ladders are further extended to a 2D hydrogen-bonded layered network through the intermolecular O-H · · · O hydrogen bond between the carboxylic group and carboxylate group of interladder HBTC(2-) ligand. Adjacent 2D layers are then packed orderly in an ABAB-type array via the intermolecular interactions of combined π-π interaction and O-H · · · O hydrogen bonds to form a 3D supramolecular architecture exhibiting 1D channels intercalated with guest water molecules. The reversible solid-state structural transformation between crystalline 1 with 1D ladderlike framework and its dehydrated powder 2, [Zn(HBTC)(BPE)0.5]n, with 2D framework via the displacement of coordinated water molecule to HBTC(2-) ligand, by thermal de/rehydrated processes has been verified by PXRD measurements. The emission of 1 and 2 is ascribed to a ligand-based transition.

In this paper, the methods based on Lyapunov stability theorem to study the stability and switching law design for the T–S fuzzy switched systems with state-driven switching method are presented. Furthermore, these methods can be applied to cases when all individual systems are unstable. The PDC is employed to design fuzzy controllers from the T–S fuzzy models. The stabilization analysis is reduced to a problem of finding a common Lyapunov function for a set of linear matrix inequalities. Finally, a numerical example and an illustrative example based on the chemical process example are given to show the merits of the proposed approach, respectively.

This paper proposes a fast macrocell label switching mechanism (MLSM) in the MPLS-WiMAX networks. The mobil station (MS) communicates with each other within macrocell, e.g., MSA in the cellA communicates with MSB in the other cell, and can be switched via the media access control (MAC) layer without involving the network layer. The average access delay of request from MSs is studied and analyzed in this paper. Finally, simulation results show that the purposed MLSM operates effectively and efficiently in terms of network throughput, average delay, and resource utilization.

Streptococcal pyrogenic exotoxin B (SPE B) is a cysteine protease expressed by Streptococcus pyogenes. The D9N, G163S, G163S/A172S, and G239D mutant proteins were expressed to study the effect of the allelic variants on their protease activity. In contrast to other mutants, the G239D mutant was ∼12-fold less active. The Gly-239 residue is located within the C-terminal S230-G239 region, which cannot be observed in the x-ray structure. The three-dimensional structure and backbone dynamics of the 28-kDa mature SPE B (mSPE B) were determined. Unlike the x-ray structure of the 40-kDa zymogen SPE B (proSPE B), we observed the interactions between the C-terminal loop and the active site residues in mSPE B. The structural differences between mSPE B and proSPE B were the conformation of the C-terminal loop and the orientation of the catalytic His-195 residue, suggesting that activation and inactivation of SPE B is involved in the His-195 side-chain rotation. Dynamics analysis of mSPE B and the mSPE B/inhibitor complexes showed that the catalytic and C-terminal loops were the most flexible regions with low order parameter values of 0.5 to 0.8 and exhibited the motion on the ps/ns timescale. These findings suggest that the flexible C-terminal loop of SPE B may play an important role in controlling the substrate binding, resulting in its broad substrate specificity.

A series of one-dimensional (1D) coordination polymers, {[Cu(en)2][M(C5O5)2(H2O)m]·xH2O}n, (M = Mn (1), m = 4, x = 2; M = Co (2), Ni (3), Cu (4), Zn (5), m = 2, x = 0; en = ethylenediamine; C5O52− = croconate, dianion of 4,5-dihydroxycyclopent-4-ene-1,2,3-trione), using [M(C5O5)2(H2O)n]2− dianion as a building block has been synthesized and characterized by the X-ray diffraction method. Structural determination reveals that, in compounds 1−5, one [M(C5O5)2(H2O)n]2− dianion coordinates via two oxygen (croconate) donors to the axial sites of two Cu(II) centers of [Cu(en)2]2+ cations to form one-dimensional (1D) linear (1, 3 and 4) or zigzag (2 and 5) chains of alternating [M(C5O5)2(H2O)n]2− and [Cu(en)2]2+ units. The croconate acts as a bridging ligand with three coordination modes as μ1,3-bismonodentate for 1, μ1,2,3-bidentate/monodentate for 2 and 5, and μ1,2,4-bidentate/monodentate for 3 and 4, respectively. In addition, a byproduct, [Cu(en)(C5O5)(H2O)]2 (6), which is cocrystallized with 4, shows a dimer...

Platinum nanoparticles were formed on oxygen plasma treated carbon nanotubes by atomic layer deposition (ALD). The treatment time of oxygen plasma generated by a microwave plasma enhanced chemical deposition system varied at 5 s to 20 s under a power of 600 W. The reaction cycle number was controlled at 50-125 and the length of pulse time for Pt precursor, O2 and N2 were set at 1 s, 5 s and 20 s, respectively. It was observed that formation of uniform and well distributed Pt nanoparticles was achieved. Furthermore, the growth rate of Pt nanoparticles could be controlled by altering the reaction cycle number and oxygen plasma treatment time. X-ray photoelectron spectroscopic analysis indicated that oxygen plasma could graft oxygen-containing functional groups to the CNTs surface, to act as the nucleation sites for growth of Pt nanoparticles.

Tris(8-hydroxyquinoline) gallium (III) (GaQ3)-Al2O3 core-shell nanowires with different shell thicknesses of Al2O3 were prepared by coating with atomic layer deposition (ALD) on GaQ3 nanowires. The photoluminescence (PL) and degradation with time of the core-shell nanowires were examined in the atmospheres of air, oxygen, argon, and water. Degradation of GaQ3 nanowires in PL intensity with time was observed in air, oxygen and water atmospheres, but not in argon. On the other hand, GaQ3-Al2O3 core-shell nanowires are only degraded in oxygen, but stable in other atmospheres. The degradation mechanism for both types of nanostructures is discussed.

Group A Streptococcus is a common pathogen that causes pharyngitis, impetigo, myositis, and lethal streptococcal toxic shock syndrome. Streptococcal pyrogenic exotoxin B (SPE B) is strongly associated with the severity of disease. SPE B is a cysteine protease and matures itself by autocatalysis. We found that SPE B was directly associated with human S-adenosylhomocysteine hydrolase (AdoHcyase), an essential factor for a delayed-type immune response. AdoHcyase protein levels and enzymatic activities were significantly higher in human cells infected with the Streptococcus pyogenes SW510 speB mutant strain than in cells infected with the NZ131 wild-type strain. SPE B also inactivated AdoHcyase, shown by a decrease in homocysteine, the main product of AdoHcyase. We found that in vivo and in vitro, SPE B induced hypermethioninemia, which is caused by an AdoHcyase defect. We also found that AdoHcyase is a substrate of SPE B cysteine protease. SPE B, therefore, potentially causes immunosuppression by cleaving AdoHcyase.

Single-crystalline Zn2GeO4 nanorods were formed by submerging Zn-containing Ge nanoparticles (ZCGNs) in water at room temperature. These nanorods with the diameter ranging from several tens to more than 100 nm and the length of several micrometers exhibit a blue-green luminescence peak at 450 nm. Due to the surface instability of Ge in water, the agglomerates of crystalline ZCGNs keep oxidizing, and gradually transform into amorphous membranes composed of Zn, Ge, and oxygen. Zn2GeO4 nanorods then grow out directly from the amorphous membranes after further aging. This novel transformation route may provide a new thinking for preparing similar 1-D Ge-based ternary oxides or other 1-D nanomaterials.

Under some rank condition, a new version of bounded real lemma, which is expressed in terms of an admissible solution of a generalized discrete-time algebraic Riccati equation (GDARE) rather than inequality, is presented for linear discrete-time descriptor systems. When a linear discrete-time descriptor system is admissible, with the H∞-norm of its transfer matrix less than a prescribed positive number γ, a constructive procedure is also given to obtain an admissible solution of the above-mentioned GDARE.

We investigate the alignment properties of nematic liquid crystal on polyimide films bombarded by Ar ion beams with a small diode sputter type ion-beam source. The alignments of nematic liquid crystal 4′-n-pentyl-4-cyanobiphenyl (5CB) on treated polyimide surface are characterized by using polarizing optical microscope and conoscope. The polyimide surfaces are also studied by using atomic force microscope and x-ray photoemission spectroscopy. We have demonstrated that the polyimide surface treated by Ar ion beams can give both homogeneous and homeotropic alignments with the same ion beam apparatus but varying the energy of ion beam and the bombarding time.

A series of coordination polymers, [M(C 5 O 5 )(dpe)] (M = Mn 1 , Fe 2 , Cd 3 and Co 4 ; dpe = 1,2-bis(4-pyridyl)ethane) with a 2D metal–organic framework (MOF) has been synthesized and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compounds 1 – 4 are isostructural and possess a 2D brick-wall-like layered framework with a rectangle grid as the basic building unit through the connectivity of metal ions with μ 3 -, μ 4 -croconates and anti -dpe ligands. Two 2D layers are then cross-linkaged by gauche -dpe ligands to complete a 2D bi-layered MOF and then extended to a 3D supramolecular architecture through π–π and C–H⋯O interactions between the croconate and pyridyl rings of dpe, which exhibit high thermo-stability and keep their crystalline forms up to 350 °C. The magnetic exchange coupling between the metal centers for compounds 1 , 2 and 4 was analyzed and based on the Curie–Weiss expression and a binuclear magnetic model. The negative values of the Weiss constant and the magnetic exchange coupling constant indicate the antiferromagnetic nature between the metal ions via the bridges of bis-bidentate adjacent μ 3 -croconate ligands.

Two metal−croconate (C5O52-) complexes, {[Cd2(bpe)(C5O5)2(H2O)]·2H2O}n (1) and {[Zn2(bpe)2(C5O5)2]}·H2O}n (2) (bpe = 1,2-bis(4-pyridyl)ethylene)) with two-dimensional (2-D) metal−organic frameworks (MOFs), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1 possesses a 2-D layered MOF with two rectangular boxes as the basic building units through the connectivity of CdII with μ3-croconates, μ5-croconates, and bpe ligands. In compound 2, a 2-D brick-wall-like layered framework is formed by using a rectangular grid as the basic building unit through the connectivity of ZnII with hybrid μ3-croconates, μ4-croconates, and bpe ligands. Two layers are then cross-linked by the other bpe ligands to complete a 2-D bilayered MOF. Both of the 2-D MOFs are extended to three-dimensional supramolecular architectures through π−π and C−H···O interactions between the croconate and the pyridyl rings of bpe, which ...

A novel solid acid hydrate H[Lu(H20)6{Re4Te4(CN) 12 }]·6H 2 O was synthesized. The compound was studied with single-crystal X-ray diffraction and wide-line 1 H NMR spectroscopy. The building blocks of the compound are formed by [Re 4 Te 4 (CN) 12 ] 4- cluster anions linked through {Lu(H 2 O) 6 } 3+ cationic complexes in infinite linear chains. The chains form a quasi 1-D structure with channels occupied with oxygen-protonated ensembles. A temperature variation triggers a two-stage evolution of intermolecular proton exchange corresponding to activation energies of 16 and 43 kJ/mol. The stages are interpreted as a step-by-step process of the solvate and coordinate water molecules becoming involved in the proton-transfer reactions. It was hypothesized that the mechanism of proton exchange includes the Grotthuss-type proton translocation in the protonated water fragments and the continual rearrangement of protonated and unprotonated fragments in the structure channels due to H 2 O molecular diffusion.

Two extended networks of Cd(II) with 2,2‘-bipyrimidine (bpym) and cyclic oxocarbon dianions CnOn2- (n = 4, 5) with formulas [Cd(C4O4)(bpym)0.5(H2O)] (1) and [Cd(C5O5)(bpym)0.5(H2O)] (2) have been synthesized and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that, in compounds 1, each Cd center lies in a seven-coordinate environment bonded to two bpym nitrogen atoms and five oxygen donors from four squarate and one water molecules. The squarate acts as a bridging ligand with two different binding modes, a tetramonodentate (μ4) and a bis-bridging (μ4) coordination mode, linking the Cd(II) ions to form a two-dimensional (2D) metal−squarate layer. Adjacent layers are then mutually linked via bridges of bis-bidentate bpym ligands constructing a three-dimensional (3D) triangular metal−organic framework (MOF). In compound 2, each Cd center lies in an eight-coordinate environment bonded to two bpym nitrogen atoms and six oxygen donors from three croconate ligands and ...

The compound trans-4,4'-azo-1,2,4-triazole (atrz) is a planar molecule with two planar triazole rings bridged by an azo group. The molecule is a good donor ligand and has an interesting π-delocalized character. In addition, intermolecular interactions in the crystalline state through π-π stacking are found between triazole rings with a very short inter-planar distance of 3.17 Å. The electron density distribution is obtained from both high resolution X-ray diffraction data at 100 K and density functional theory (DFT) calculations using the ωB97X-D functional. Bond characterization is performed in terms of the charge density distribution and the associated topological properties. The Laplacian distribution around each atom reveals the shape of the valence-shell charge concentration and demonstrates a sp(2) hybrid orbital shape for each atom in the molecule. The π-delocalization of the planar molecule is further illustrated by the Fermi-hole distribution. The weak intermolecular π-π interactions and hydrogen bonds are further illustrated by the Hirshfeld surface. The energies of weak intermolecular π-π interactions and hydrogen bonds have been calculated using ωB97X-D/6-311++G(3df,2p) at experimental geometry.

A new polymeric complex, [Cd(bpym) 0.5 (N 3 ) 2 ] n (bpym = 2,2'-bipyrimidine) has been synthesized and characterized by spectroscopic, elemental analyses and single crystal X-ray diffraction. The title compound crystallizes in the monoclinic system, space group P2 1 /c, with chemical formula C 4 H 3 CdN 8 , a = 7.6763(5), b = 13.1539(9), c = 7.9693(5) A, β = 109.988(1)°, and Z = 4. Structural determination reveals that the coordination environment of the cadmium atoms is distorted octahedral, consisting of two nitrogen donors of one bpym and four nitrogen donors of four azide ligands. The azide ligand acts as a bridging ligand with two different bridging modes, an end-on (μ 1,1 -) and an end-to-end (μ 1,3 -) coordination mode, linking the Cd" ions to form a two-dimensional layer metal-organic framework (MOF), which get crosslinked by the bridges of bis-bidentate bpym ligands to form a novel 3D network.

This letter proposes a novel geographic channel assignment (GCA) framework for dynamic channel allocation (DCA) in broadband wireless access networks (BWANs). The proposed GCA scheme is based on the characteristics of radio propagation, which focuses on the relationship between transmission distances and communication parameters, e.g., signal-to-noise ratio (SNR) etc., and uses a signal-aware distance estimation scheme to determinate an appropriate channel for communication. This method significantly increases the capacity of the BWA system. Simulation results show that the GCA framework can yield approximate two times throughput of the IEEE 802.16 standard specifications as well as obtain significantly lower call blocking probability compared with classical channel assignment methods.

Two extended coordination frameworks of CdII–squarate complexes with the formulas [Cd2(C4O4)2.5(H2O)4](dpaH)·1.5(H2O) (1) and [Cd(C4O4)(dpa)(H2O)] (2) (dpa = 2,2′-dipyridylamine) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1 consists of a free monoprotonated 2,2′-dipyridylamine ion (dpaH+) and a two-dimensional (2D) anionic, layered framework, {[Cd2(C4O4)2.5(H2O)4]–}, which is formed with two antiprismatic square-boxes as the fundamental building unit through the connection between CdII ions and hybrid μ1,2,3-, μ1,2,3,4-squarates. Each square-box acts as a host for the inclusion of one pyridine ring of dpaH+. Adjacent dpaH+ cations are then self-assembled by the parallel alignment of the other pyridine ring of dpaH+ to complete a 3D network with one-dimensional (1D) channels intercalated by water molecules. Compound 2 contains a distorted octahedral CdII center coordinated by two squarates, two waters and one dpa ligand to form a 1D 2-legged, ladder-like framework by the connection of a [Cd(dpa)(μ2-H2O)]24+ dimeric unit and a μ1,2-squarate. Weak π–π stacking interaction and hydrogen bonds of N–H···O, O–H···O and C–H···O among the squarate, water and dpa ligands provide additional intra- and intermolecular interactions on the stabilization of these two polymeric frameworks. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Two metal coordination polymers with general formula [M(dpa)(C4O4)(H2O)] [M = Co (1), Ni (2), Zn (3); dpa = 2,2'-dipyridylamine] and [Cu(dpa)(C4O4)(H2O)]2·H2O (4) have been synthesized under hydrothermal conditions. The single-crystal X-ray analyses reveal that compounds 1–3 are isostructural and possess distorted octahedral metal centers coordinated by two squarates, one dpa, and two water molecules. A 1D two-legged ladder-like framework is formed by interconnection of the water-bridged [M(dpa)(μ2-OH2)]24+ dimeric fragments and μ1,2-squarate ligands. Intra- and intermolecular hydrogen bonds between squarate, water, and dpa ligands, as well as the π-π stacking interaction of the pyridyl ring in the dpa ligands, provide extra forces to stabilize the extended network. Conversely, the molecular structure of compound 4 contains two distorted square-pyramidal CuII centers coordinated by two squarates, one dpa ligand, and one water molecule. The squarates adopt a μ1,2-binding mode to link the Cu centers and form a 1D helical chain. For compound 2, the magnetic exchange couplings between metal centers are analyzed with a binuclear magnetic model. The resulting negative magnetic exchange coupling constant indicates an antiferromagnetic interaction within the dimers. The magnetic behavior of compound 4 is typical of paramagnetic CuII ions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Intra and intermolecular interactions of heptasulfur imide (S7NH) are investigated in terms of topological properties analyses, such analyses are applied to both experimental (multipole model) and theoretically calculated (DFT and PDFT calculations) charge densities of the isolated molecule and of the crystal. The same analyses are also applied to a multipole model density obtained from theoretically (PDFT) derived structural amplitudes. The covalent bond character of S–N, N–H and S–S bonds are well described in terms of density, rb, and total energy density, Hb, at the bond critical point rc, though it is clear that the S–S bonds are weaker shared interactions than those of N–H and S–N bonds. Lone pair electron regions of sulfur and nitrogen atoms are revealed as the local charge concentration site from the Laplacian of charge density. The even weaker intermolecular interactions are well characterized; these include the N–H/S hydrogen bonding, N/S binding interactions and S/S binding interactions. All these intermolecular binding interactions are closed-shell interactions. The Laplacian of charge density demonstrates a directional intermolecular binding interaction. The corresponding intermolecular binding energies are derived by MP2/6-311CG(d,p) calculations. Atomic graph of each atom of the molecule is described in detail by the vertices, edges and faces of the polyhedron around the nucleus to illustrate such directional interactions. q 2004 Elsevier Ltd. All rights reserved.

A new right angle-shaped ligand, 2,2‘-bis(4-pyridyl)-9,9‘-spirobifluorene (L), is designed and synthesized. Treatment of L with silver(I) ions leads to linear polymeric metal−organic frameworks, [Ag(L)2]+ (1), that feature square subunits. Single-crystal X-ray analysis reveals that [Ag(L)2]+ has a one-dimensional double-stranded polymeric chain comprising square grids with cavity dimensions of ca. 8 A × 8 A. By π−π stacking of adjacent double-stranded chains, the structure is extended into a two-dimensional (2D) layer framework with a unique quasi-aperture (dimensions of ca. 14 A × 8 A). Each 2D layer is inclined and mutually interpenetrated, which gives rise to the three-dimensional interlocked network structure. Compound 1·(BF4)(CH3OH) crystallizes in the monoclinic system, space group C2/c, with chemical formula C71H49N4OBF4Ag, a = 25.709(1) A, b = 14.4164(6) A, c = 15.6865(7) A, β = 109.220(2)°, and Z = 4.

A new mixed-ligands metal-coordination polymer, [Cd(C4O4)(bipy)(H2O)2] (1), (bipy=4,4′-bipyridine), was synthesized under hydrothermal condition and characterized by X-ray diffraction method. A three-dimensional interpenetrating network with one-dimensional channels intercalating water molecules undergoes a reversible hydration-dehydration process upon a cooling-heating cycles associated with distinct color change and structural variation.

Topological analyses of experimental and theoretical calculated electron densities of 1,3,5,7-tetra-tert-butyl-s-indacene provide bond characterizations of the chemical bond and of the π-delocalization. A weak C sp 3 —H...H—C sp 2 -type intramolecular dihydrogen interaction (DHI) is identified through this analysis.

Two coordination polymers with the formula of [M 2 (DPA) 2 (C 4 O 4 )(C 2 O 4 )] ∞ (M=Cu 1 , Zn 2 ; DPA=dipyridylamine) were synthesized under hydrothermal conditions. Both complexes are crystallized in triclinic system, space group P 1 with the cell parameters: a=8.3078(3) A , b=9.1192(3) A , c=9.2316(3) A , α=115.164(1)°, β=94.283(1)°, γ=103.559(1)°, V=603.17(4) A 3 , Z=2 for complex 1 and a=8.5348(2) A , b=9.0451(2) A , c=9.0862(3) A , α=114.305(1)°, β=100.493(1)°, γ=97.318(1)°, V=612.34(2) A 3 , Z=2 for complex 2 , respectively. X-ray single-crystal structural determinations reveal that these two complexes are both composed of one-dimensional zigzag chains built up via the [M(DPA)] 2+ fragments and alternately bridged bidentate μ 1,3 -C 4 O 4 2− , tetradentate C 2 O 4 2− ligands. The coordination environments of the M(II) centers adopt a slightly distorted trigonal bipyramid bonded with two N atoms of DPA, one O atom of squatate and two O atoms of oxalates. The intrachains N–H⋯O and C–H⋯O hydrogen bonds play an important role on the additional stabilization in constructing the open frameworks.

A new unsymmetrical bisdithiolene nickel complex Ni(Et 2 dazdt)(mnt) was synthesized and structurally characterized, where Et 2 dazdt and mnt denote 1,4-diethyl-perhydrodiazepine-2,3-dithione and maleonitrildithiolate, respectively. Its crystal structure and absorption spectrum were determined and compared to those of Ni(Et 2 pipdt)(mnt), where Et 2 pipdt is 1,4-diethyl-piperazine-2,3-dithione. X-ray diffraction analysis reveals that the Ni(S 2 C 2 ) 2 moiety of Ni(Et 2 dazdt)(mnt) is not planar due to the twist conformation of a seven-member ring of Et 2 dazdt ligand. The twisting of Et 2 pipdt is less severe and NiS 4 center of Ni(Et 2 pipdt)-(mnt) possesses a closer to planar conformation than that of Ni(Et2dazdt)(mnt). Unlike Ni(Et 2 pipdt)(mnt), Ni(dazdt)(mnt) shows two major separated absorption bands in the visible and near-IR region, although both absorption bands show negative solvatochromism similar to that of Ni(Et2pipdt)(mnt).

A series of linear pentanuclear cobalt complexes, including both neutral and one-electron oxidized forms, have been synthesized. The one-electron oxidation products were prepared either by reaction with silver salts or by bulk electrolysis. In all of these complexes, the pentacobalt chain adopts a symmetrical arrangement and is helically wrapped by four tpda [the dianion of N,N′-bis(α-pyridyl)-2,6-diaminopyridine] ligands. Two sets of Co–Co bond distances are observed, in which the average internal (inner) bond is about 0.06 A shorter than the external (outer) one. After one-electron oxidation, the average Co–Co and Co–N bond distances are not significantly different from those of the neutral analogues, whereas the Co–X (X = axial ligand) bond lengths exhibit a slight decrease in length. All of these complexes show two reversible redox couples at about +0.35 and +0.85 V (vs. Ag/AgCl). The first oxidation is a metal-centered reaction and the product has been structurally characterized. The second oxidation product is stable on the time scale of spectroelectrochemistry, but undergoes reduction to form the corresponding one-electron oxidation product under the crystallization conditions. The NMR results are consistent with the paramagnetism of both the neutral and oxidized complexes. The magnetic measurements indicate that the neutral and one-electron oxidized molecules have spin states of S = 1/2 and 1, respectively.

In this work, the anionic building blocks [M(C5O5)2(H2O2)2]2- (M = Ni, Cu) are synthesized easily, and their structures are unique and interesting in the coordination chemistry of croconate ligand (C5O52-) with the first transition metal. The [M(C5O5)2(H2O2)2]2- moieties act as a dianionic template, and sodium acts as interconnecting cations to build up a three-dimensional framework.

The hydrothermal reaction of CuCl2·2H2O, H4edta, and H2O yields [Cu(H2edta)]n complex in which the Cu atom is surrounded by two nitrogen donors and three oxygen donors of the H2edta2- ligand and the sixth coordinated site is coordinated by the oxygen atom of the nonprotonated acetate group in the neighboring complex to form a polymeric helical chain structure.

NMDA receptor signaling plays a complex role in CREB activation and CREB-mediated gene transcription, depending on the subcellular location of NMDA receptors, as well as how strongly they are activated. However, it is not known whether Rac1, the prototype of Rac GTPase, plays a role in neuronal CREB activation induced by NMDA receptor signaling. Here, we report that NSC23766, a widely used specific Rac1 inhibitor, inhibits basal CREB phosphorylation at S133 (pCREB) and antagonizes changes in pCREB levels induced by NMDA bath application in rat cortical neurons. Unexpectedly, we found that NSC23766 affects the levels of neuronal pCREB in a Rac1-independent manner. Instead, our results indicate that NSC23766 can directly regulate NMDA receptors as indicated by their strong effects on both exogenous and synaptically evoked NMDA receptor-mediated currents in mouse and rat neurons, respectively. Our findings strongly suggest that Rac1 does not affect pCREB signaling in cortical neurons and reveal that NSC23766 could be a novel NMDA receptor antagonist.

A single, low dose of the NMDA receptor antagonist ketamine produces rapid antidepressant actions in treatment-resistant depressed patients. Understanding the cellular mechanisms underlying this will lead to new therapies for treating major depression. NMDARs are heteromultimeric complexes formed through association of two GluN1 and two GluN2 subunits. We show that in vivo deletion of GluN2B, only from principal cortical neurons, mimics and occludes ketamine's actions on depression-like behavior and excitatory synaptic transmission. Furthermore, ketamine-induced increases in mTOR activation and synaptic protein synthesis were mimicked and occluded in 2BΔCtx mice. We show here that cortical GluN2B-containing NMDARs are uniquely activated by ambient glutamate to regulate levels of excitatory synaptic transmission. Together these data predict a novel cellular mechanism that explains ketamine's rapid antidepressant actions. In this model, basal glutamatergic neurotransmission sensed by cortical GluN2B-containing NMDARs regulates excitatory synaptic strength in PFC determining basal levels of depression-like behavior.