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The b-axis oriented orthorhombic YMnO3 (o-YMnO3) epitaxial films on a YAlO3 (010) substrate were fabricated with pulsed-laser deposition. The anisotropic orbital occupation and Jahn-Teller (JT) distortion of an o-YMnO3 film were investigated with polarization-dependent x-ray absorption spectra and configuration-interaction multiplet-cluster calculations. A significant energy difference, ∼3.8 eV, for the main white line along E//b and E//a in polarization-dependent Mn K-edge spectra of o-YMnO3 indicates an extraordinary JT distortion and significant anisotropic Mn-O bonding within the ab plane in the o-YMnO3 film. Most importantly, although the orbital occupation of 3d electrons in o-YMnO3 films is almost the same as that in single crystalline o-DyMnO3, the JT distortion of o-YMnO3 films is larger than that of single crystalline o-DyMnO3, deduced from the multiplet calculations. We speculate that this JT distortion predominantly contributes to the origin of the cycloidal spin deformation in bulk o-YMnO3, because of a suppressed nearest-neighbor superexchange interaction and an enhanced next-nearest-neighbor superexchange interaction. These complementary results provide insight into the origin of the E-type magnetic configuration of o-YMnO3. [ABSTRACT FROM AUTHOR]

The crystal structures, magnetic and dielectric properties were evaluated for Sm1.5Sr0.5Ni1-xMnxO4 (x = 0.03, 0.05, 0.1) ceramics. The Rietveld results of X-ray diffraction patterns confirmed single orthorhombic phase with the space group of Bmab (64) were obtained in Sm1.5Sr0.5Ni1-xMnxO4 (x = 0.03, 0.05) ceramics, while in Sm1.5Sr0.5Ni0.9Mn0.1O4 ceramics, apart from the main orthorhombic phase, a tiny secondary phase was detected. A magnetism characteristic of a spin glass was found in Sm1.5Sr0.5NiO4, while a complicated magnetic phenomenon was observed in Sm1.5Sr0.5Ni0.9Mn0.1O4 ceramics. The giant dielectric response was observed in these ceramics, and dielectric loss decreased with increasing the content of manganese ions. After comparing the activation energies of dielectric relaxation and electrical conduction, the low-temperature giant dielectric response should be attributed to the adiabatic small polaronic hopping process, while at high-temperature, the low frequency relaxation was mainly attributed to the grain boundary effect. The suppression of dielectric loss should be benefited from the various polar region caused by Mn-substitution. [ABSTRACT FROM AUTHOR]

Biohydrometallurgy is generally considered as a green technology for the recycling of industrial solid waste. In this study, an indigenous fungal strain named Y5 with the ability of high-yielding organic acids was isolated and applied in bioleaching of waste printed circuit boards (PCBs). The strain Y5 was identified as Penicillium chrysogenum by morphological and molecular identification. Meanwhile, we investigated that an optimal set of culturing conditions for the fungal growth and acids secretion was 15 g/L glucose with initial pH 5.0, temperature 25°C and shaking speed 120 rpm in shaken flasks culture. Moreover, three bioleaching processes such as one-step, two-step and spent medium processes were conducted to extract copper from waste PCBs. Spent medium bioleaching showed higher copper extraction percentage and it was 47% under 5%(w/v) pulp density. Transmission electron microscope (TEM) observation combining with energy dispersive analysis of X-rays (EDAX) showed that the leached metal ions did not obviously damage the hypha cells. All above results indicated that P . chrysogenum strain Y5 has the tolerance to metal ions, suggesting its potential in recycling of metals from waste PCBs in industry. [ABSTRACT FROM AUTHOR]

The effects of secondary magnetic field originating from a permanent magnet on deposition rate, crystalline structure and photoelectric properties of Al-doped ZnO (AZO) films prepared by RF magnetron sputtering were systematically investigated. X-ray diffraction demonstrated that the films prepared using a secondary magnetic field were well aligned and textured along (002) orientation. SEM micrographs revealed that the grains became more compact and homogeneous with fewer defects in comparison to those grown by conventional magnetron sputtering (CMS). The deposition rate and lowest resistance of films prepared in the presence of a secondary magnetic field were 19.9nm/min and 12.88Ω/, respectively. The average transmittance of all films in visible range was over 85% when the sputtering time was less than 60min. The secondary magnetic field had a small influence on the transmittance of the films, but it caused a larger blue shift of the absorbance edge. Numerical simulations showed that the secondary magnetic field significantly changed the intensity and distribution of the transverse magnetic field in discharge space and caused a higher target current density. [ABSTRACT FROM AUTHOR]

X-Ray single-crystal diffraction has been the most straightforward and important technique in structural determination of crystalline materials for understanding their structure-property relationships. This powerful tool can be used to directly visualize the precise and detailed structural information of porous coordination polymers or metal-organic frameworks at different states, which are unique for their flexible host frameworks compared with conventional adsorbents. With a series of selected recent examples, this review gives a brief overview of single-crystal X-ray diffraction studies and single-crystal to single-crystal transformations of porous coordination polymers under various chemical and physical stimuli such as solvent and gas sorption/desorption/exchange, chemical reaction and temperature change. [ABSTRACT FROM AUTHOR]

Effects of oxygen vacancies on the dielectric, electrical, and ferroelectric properties of Ba4Nd2Fe2Nb8O30 ceramics were investigated. A dielectric relaxation above Tc can be ascribed to the trap-controlled ac conduction around doubly ionized oxygen vacancies. The dc conductivity of the N2-annealed and O2-annealed samples is attributed to the long-range motion of the ..., and that of the as-sintered sample is considered to be governed by the electronic and oxygen-vacancy ionic mixed conduction mechanism. Low concentration and random distributed oxygen vacancies are propitious to the domain switching, while high concentration and allied oxygen defects hinder the domain-wall movement. [ABSTRACT FROM AUTHOR]

The complex metal oxide SrCo0.5Ru0.5O3-δ possesses a slightly distorted perovskite crystal structure. Its insulating nature infers a well-defined charge distribution, and the six-fold coordinated transition metals have the oxidation states +5 for ruthenium and +3 for cobalt as observed by X-ray spectroscopy. We have discovered that Co3+ ion is purely high-spin at room temperature, which is unique for a Co3+ in an octahedral oxygen surrounding. We attribute this to the crystal field interaction being weaker than the Hund's-rule exchange due to a relatively large mean Co-O distances of 1.98(2) Å, as obtained by EXAFS and X-ray diffraction experiments. A gradual high-to-low spin state transition is completed by applying high hydrostatic pressure of up to 40 GPa. Across this spin state transition, the Co Kβ emission spectra can be fully explained by a weighted sum of the high-spin and low-spin spectra. Thereby is the much debated intermediate spin state of Co3+ absent in this material. These results allow us to draw an energy diagram depicting relative stabilities of the high-, intermediate-, and low-spin states as functions of the metal-oxygen bond length for a Co3+ ion in an octahedral coordination. [ABSTRACT FROM AUTHOR]

Bi nanoparticles embedded in a SiO2 matrix were prepared via the high energy ball milling method. The melting behavior of Bi nanoparticles was studied by means of differential scanning calorimetry (DSC) and high-temperature in situ X-ray diffraction (XRD). DSC cannot distinguish the surface melting from ‘bulk’ melting of the Bi nanoparticles. The XRD intensity of the Bi nanoparticles decreases progressively during the in situ heating process. The variation in the normalized integrated XRD intensity versus temperature is related to the average grain size of Bi nanoparticles. Considering the effects of temperature on Debye—Waller factor and Lorentz-polarization factor, we discuss the XRD results in accordance with surface melting. Our results show that the in situ XRD technique is effective to explore the surface melting of nanoparticles. [ABSTRACT FROM AUTHOR]

The structural evolution of Sr1− xSm1+ xAl1− xTi xO4 ( x=0, 0.05, 0.10, and 0.15) microwave dielectric ceramics was investigated together with its effects on dielectric loss. Through the analysis of Rietveld refinement of powder X-ray diffraction, the normalized bond length and normalized bond valence showed an abnormal variation of Sr/Sm-O(2b) and Al/Ti-O(2) bonds from x=0.10 to x=0.15. The abnormal variation related to these bonds in Raman spectra and IR reflectivity spectra was observed. IR reflectivity spectra were calculated by the classical oscillator model fitting to evaluate the intrinsic loss. The calculated Q × f value and the measured ones both decreased as x increased, and a sharp decrease from x=0.10 to x=0.15 was observed. The decreased tolerance factor should be responsible for the decreased Q × f value. Moreover, the abnormal evolution of Sr/Sm-O(2)-Al/Ti bonding that can cause an extra local stress should be responsible for the sharp decrease from x=0.10 to x=0.15 in Q × f value. [ABSTRACT FROM AUTHOR]

The improvement in microwave dielectric characteristics by Ca substitution in SrLaAlO4 ceramics together with the stability of K2NiF4 structure were investigated. X-ray diffraction analysis and the scattering electron images combined with EDS analysis indicated that the matrix phase was a solid solution with a composition represented by the chemical formula Sr1-xCaxLaAlO4 in the entire range of 0≤x≤0.9, and minor amount of LaAlO3 secondary phase was detected only in the composition of x = 0.8 and 0.9. The relative permittivity increased slightly with increasing x, while the temperature coefficient of resonant frequency was tuned from -33.9 to -14.7 ppm/°C. The significant improvement of Qf value was achieved in the present ceramics with increasing x and reached the maximum at x = 0.4, but it turned to decrease for x > 0.4. The best combination of microwave dielectric characteristics was achieved at x = 0.4: ϵr = 18.1, Qf = 150 500 GHz, and τf = -26.2 ppm/°C. [ABSTRACT FROM AUTHOR]

Photoluminescence and X-ray absorption spectroscopy (XAS) measurement were used to characterize the near-band edge (NBE) emission intensity and electronic structure of as-implanted GaN nanowires (NWs) that had been implanted with Eu ions to different fluences. The N K- and Ga L3-edge of total electron yield XAS spectra showed the formation of N interstitials (Ni) and dangling bond (Ndb) point defects and the formation of metallic Ga layers on the surface of NWs. X-ray diffraction, Ga K- and L3-edge of total fluorescence yield XAS spectra consistently revealed the wurtzite structure of the as-implanted NWs up to the highest fluence. The ratio of absorption intensity found in sp3 and sp2 environment and the NBE intensity were strongly affected by the implantation. It is suggested that the decrease of NBE intensity was closely related to the change from sp3 to sp2 environment. The absorption intensity ratio between the as-grown and as-implanted samples of Ndb and Ni was directly proportional to the fluences indicating that these defects are preferentially formed during implantation. [ABSTRACT FROM AUTHOR]

Nanoscaled Y3Al5O12:Ce (YAG:Ce) particles prepared through a coprecipitation method and heated to elevated temperatures were treated in different weights with tetraethyl orthosilicate at room temperature for surface coating. The IR absorption measurements attested to the presence of silica in YAG:Ce by a broad absorption band at 1000–1400 cm−1, while maintaining a cubic structure and constant lattice parameters as revealed from the X-ray diffraction analysis. Transmission electron micrographs also presented the encapsulation of YAG:Ce nanoparticles in silica as the IR results. The optical properties of photoluminescence (PL) of these silica-coated YAG:Ce were found to depend on the quantity of YAG:Ce nanoparticles in the coating solution with an optimal weight ratio of 0.16 (silica/YAG:Ce). The increased PL intensity of these YAG:Ce after silica coating was proposed to result from the quenching inhibition of surface states in YAG:Ce nanoparticles and the increased light extraction from the silica/YAG:Ce interface. [ABSTRACT FROM AUTHOR]

High molecular weight poly(butylene succinate) (PBSu), poly(propylene succinate), and PBSu-rich copolyesters were synthesized using an effective catalyst, titanium tetraisopropoxide. The compositions of the copolyesters were determined in three ways from 1H and 13C NMR spectra, and good agreement between the results was obtained. The analysis of the carbonyl carbon spectra indicates a random distribution of the comonomers. Thermal properties were studied using a differential scanning calorimeter and a thermogravimetric analyzer. No significant difference exists among the thermal stabilities of these polyesters. However, the window between the glass transition and the melting temperatures becomes narrower with the increase in the concentration of propylene succinate in the copolymers. Additionally, the cold crystallization ability reduces considerably. Wide-angle X-ray diffractograms of isothermally crystallized copolyesters also follow the same trend. [ABSTRACT FROM AUTHOR]

SrSmAlO4 microwave dielectric ceramics were modified by Sr/Ti cosubstitution for Sm/Al. The effects of radius difference of A-site ions on the microwave dielectric characteristics were investigated together with the structure. Sr1+ xSm1− xAl1− xTi xO4 ( x=0, 0.05, 0.10, and 0.15) ceramics were prepared by a solid-state reaction approach. X-ray diffraction studies revealed a single-phase K2NiF4-type solid solution with corresponding peaks shifting to lower 2θ as x increased. Minor inhomogeneous grain morphology for x=0.05 and a trace amount of second phases for x=0.10, 0.15 were detected by backscattered-electron microscopy and energy-dispersive X-ray analysis. With increasing Sr/Ti cosubstitution, the dielectric constant ℇr increased from 18.4 to 20.4, and the temperature coefficient of resonant frequency τ f was adjusted from −1.8 to 7.4 ppm/°C almost linearly. However, the Q× f value decreased from 74,500 GHz at x=0–53,000 GHz at x=0.15. The internal stresses caused by the decreased tolerance factor and the large ionic radii difference between Sr2+ and Sm3+ should be the predominant reasons for such a decrease in the Q× f value. The high-resolution transmission electron microscopic results revealed an increase in the lattice distortion with increasing Sr/Ti cosubstitution, and subsequently supported the above conclusion upon the increased internal stresses. [ABSTRACT FROM AUTHOR]

The crystal structure and dielectric characteristics were evaluated for Ba4Sm2Ti4Ta6O30 and Ba5SmTi3Ta7O30 ceramics. The X-ray diffraction patterns confirmed the tetragonal tungsten bronze structure with space group P4 bm. A normal ferroelectric phase transition was observed at 332 K for the former, while the typical relaxor ferroelectric behavior with a spin glass nature was determined for the latter, where a broad permittivity peak with a strong frequency dispersion was observed around 150 K, which followed the Vogel–Fulcher relationship well. These different dielectric behaviors originated from the different crystal structures governed by the occupancy configuration of cations at A1 and A2 sites. [ABSTRACT FROM AUTHOR]

Copper nanoparticles (Cu-NPs) have been electrochemically synthesized onto a poly(o-phenylenediamine) (P0PD-) coated glassy carbon electrode (GCE). Electrochemical properties and surface characterizations were studied using cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. Cyclic voltammetry, AFM, SEM, and XRD confirmed the presence of Cu-NPs on the electrode surface. Cu-NPs are firmly stabilized by surface attachment of the PoPD functionality that can be attached to the electrode surface, thus becoming an integral part of the polymer backbone. The Cu-NPs-polymer film-coated GCE (Cu-NPs/PoPD/GCE) showed excellent electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2) and nitrite (NO2-). Amperometry was carried out to determine the concentration of H202 and NO2- at -0.3 V. The dependence of the current response on the H2O2 concentration was explored under neutral conditions, and an excellent linear concentration range from 1.0 x 106 to 1.0 x 10-3 M was found. The Cu-NPs/PoPD/GCE allows highly sensitive, low working potential, stable, and fast amperometric sensing of H2O, and NOT. This is promising for the future development of nonenzymatic sensors. The real-sample analysis of commercial H2O2 samples was performed using the proposed method, and the obtained results are satisfactory. [ABSTRACT FROM AUTHOR]

(Ca1+ xSm1− x)(Al1− xTi x)O4 (0≤ x≤0.4) ceramics were synthesized by solid-state reaction method and their microstructures and microwave dielectric properties were investigated. X-ray diffraction analysis and energy-dispersive X-ray analysis indicated that the matrix phase was a solid solution with a composition represented by the chemical formula (Ca1+ xSm1− x) (Al1− xTi x)O4 and minor amount of (Ca,Sm)(Al,Ti)O3 secondary phase was detected. Ca/Ti cosubstitution could significantly improve the microwave dielectric characteristics of CaSmAlO4 ceramics, and the excellent microwave dielectric characteristics were obtained in the modified ceramics as ℇr=19–23, Q× f=49 100–118 700 GHz, and τf=−15–15 ppm/°C. [ABSTRACT FROM AUTHOR]

Solvothermal and solution reactions of a V-shaped organic ligand 4,4′-oxybis(benzoic acid) (H2oba) and Cu(NO3)2yield two porous coordination polymers, namely [Cu(oba)(dmso)] (MCF-21) and [Cu2(oba)2(dmf)(C2H5OH)]·(dmf)2(H2O) (MCF-22·guest) (dmso = dimethyl sulfoxide, dmf = dimethylformamide), respectively. Single-crystal X-ray analyses reveal that the metal carboxylate backbones of MCF-21and MCF-22·guestare framework-isomeric as two uninodal four-connected nets, i.e.a two-dimensional (2-D) 44layer and a 3-fold interpenetrated lvt (4284) three-dimensional (3-D) network, respectively. After removing the solvent molecules, MCF-21retains a rigid 2-D framework, but MCF-22·guestexhibits either rigid or dynamic behavior depending on the degree of desolvation, which is confirmed by powder X-ray diffraction and sorption isotherms. Meanwhile, the different sorption behavior of the framework-isomeric materials is elucidated by the discrepancies of their pore dimensions and framework rigidities. [ABSTRACT FROM AUTHOR]

A series of new phosphors of CaAlBO4:RE3+ (RE = Ce, Tb, Eu) were synthesized by conventional solid-state reactions. The X-ray diffraction data indicate that a pure phase of CaAlBO4:RE3+ can be successfully obtained. The photoluminescence (PL) spectra, quantum efficiency, and CIE coordinates of CaAlBO4:RE3+ were investigated. The PL and PL excitation spectra indicate that the emission wavelengths of CaAlBO4:Ce3+ are 372 and 398 nm (with full width at half maximum of 33 nm) attributed to the 4f65d-4f7 transition of the Ce3+ activator, respectively. CaAlBO4:Tb3+ displays green emission at 483, 543, 584, and 620 nm, while CaAlBO4:Eu3+ shows a dominating emission peak at 621 nm, which is attributed to the Eu3+ 5D0 - 7F2 transition. The quantum efficiencies of optimized CaAlBO4:Ce3+, CaAlBO4:Tb3+, and CaAlBO4:Eu3+ were found to be 43, 21, and 19%, respectively. The phosphors may provide a new kind of luminescent material under UV excitation. [ABSTRACT FROM AUTHOR]

We have investigated the luminescence of a series of M5Eu(WO4)4-x(MoO4)x (M = Li, Na, K) phosphors and discovered that Na5Eu(WO4)4-x(MoO4)x (0 ≤ x ≤ 4.0) exhibit the most intense red emission among the three investigated. Powder X-ray diffraction investigations show that a complete solid solution can be formed in the indicated composition range. The effect of chemical compositions on the luminescence properties of Na5Eu(WO4)4-x(MoO4). has been investigated and discussed. The Commission International de l'Eclairage chromaticity coordinates were found to be (0.66,0.33) for Na5Eu(WO4)4-x(MoO4)x, which reaches the same level as that of the Y2O2S:Eu3+ commodity. The color-rendering index (Ra) of a typical white-light-light emitting diode (WL-LED) based on Na5Eu(WO4)2(MoO4)2 was found to be 82.3, higher than that (i.e., Ra ∼ 70.8) obtained for the WL-LED fabricated using the commodity of La2O2S:Eu3+ when the WL-LEDs were operated at a forward-bias current (If) of 20 mA at room temperature. Na5Eu(WO4)4-x(MoO4), is therefore suggested to be a potential red-emitting phosphor for WL-LED. [ABSTRACT FROM AUTHOR]

Thermal expansion behaviors of Ba6−3 xLn8+2 xTi18O54 (Ln=La, Nd, and Sm, x=0.5, 0.67, and 0.75) ceramics were determined by dilatometric measurement. The samples of all investigated compositions expanded nearly linearly with increasing temperature in the range of 20°–1200°C. Their thermal expansion coefficients were determined to be 10.7–11.4 ppm/°C. A discontinuous change in sample size was observed at about 1350°C for each composition, indicating the existence of a phase transition. As determined by the high-resolution X-ray diffraction analysis, the phase constitution and the lattice parameters of Ba6−3 xSm8+2 xTi18O54 ceramics were maintained in the quenched samples. The origin of the phase transition was discussed thoroughly. Phase equilibrium in the BaTiO3–Ln2/3TiO3 system was reviewed by considering the phase transition. [ABSTRACT FROM AUTHOR]

Oxygen absorption in YBaCo4O7+δ was studied by in situ XRD and by XANES spectroscopy. Unit cell of 10.875 x 10.168 x 12.788 ų (Pnna) was found for the oxygenated phase. XANES shows that oxygen absorption increases the number of different crystallographic sites for Co. [ABSTRACT FROM AUTHOR]

Two new two-dimensional (2D) heterometal coordination polymers [Cu2M(tzdc)2(H2O)2]∙2H2O [M = Fe2+ (1) or Mn2+ (2); tzdc3- = 1,2,3-triazole-4,5-dicarboxylate] were assembled by using the tzdc3-, Cu2+, and Fe2+/Mn2+ ions. Single-crystal X-ray analysis reveals that the two compounds consist of mixed-spin microporous Kagomé layers, which are packed into three-dimensional structures by hydrogen bonding and interlayer weak Cu⋯O interactions. When heated, they can release in a stepwise manner the uncoordinated and coordinated water molecules to produce dehydrated phases (1′ and 2′), respectively, which are stable up to ~300 °C. The structures of 1′ and 2′ were determined by powder X-ray diffraction analysis, which reveals a change in the coordination sphere of Fe2+/Mn2+ ions from an octahedron to an elongated 4+2 form, and a microporous-to-nonporous structural transformation involving intralayer wrinkling and interlayer superimposition. When the dehydrated samples are exposed to air, they can return to the hydrated phases quickly by adsorption of water molecules. Accordingly, a reversible change in magnetism between the ferrimagnetic character of the hydrated samples and the suppressed ferrimagnetic character of the dehydrated samples was found in this reversible dehydration and rehydration. These facts indicate these 2D heterometal coordination polymers are unique flexible 2D dynamic magnetic materials. [ABSTRACT FROM AUTHOR]

Conventional adsorbents preferentially adsorb the small, high-polarity, and unsaturated 1,3-butadiene molecule over the other C4 hydrocarbons from which it must be separated. We show from single-crystal x-ray diffraction and computational simulation that a hydrophilic metal-organic framework, [Zn2(btm)2], where H2btm is bis(5-methyl-1H-1,2,4-triazol-3-yl)methane, has quasi-discrete pores that can induce conformational changes in the flexible guest molecules, weakening 1,3-butadiene adsorption through a large bending energy penalty. In a breakthrough operation at ambient temperature and pressure, this guest conformation–controlling adsorbent eluted 1,3-butadiene first, then butane, butene, and isobutene. Thus, 1,3-butadiene can be efficiently purified (≥99.5%) while avoiding high-temperature conditions that can lead to its undesirable polymerization. [ABSTRACT FROM AUTHOR]

In organic field-effect transistors (OFETs), the quality of charge-transport pathway, controlled by crystal structures of organic semiconductors (OSCs), strongly affects the performance of the device. To achieve higher charge mobility, solution-processed single-crystal (SPSC) techniques have been used to decrease crystal defects by aligning the crystals of OSCs in the in-plane direction. Nonetheless, through SPSC techniques, whether the crystalline lattices are well-aligned in the out-of-plane direction and how the out-of-plane lattice misorientaion affects OFET performances remain unclear. Here, a characterization protocol based on polarized optical microscope, X-ray diffraction, and electron diffraction is established to identify the lattice structure, the in-plane and out-of-plane lattice alignment in the crystal array of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN). Regardless of the solvents used in the PDMS-assisted crystallization, the characterization protocol confirms that all the crystal arrays share the same lattice structure (form I phase), and have similar in-plane lattice alignment. However, TIPS-PEN molecules have sufficient time to unify their out-of-plane orientation and prevent the formation of low angle grain boundary (LAGB) during crystal growth if high boiling temperature solvents are used. The improved out-of-plane lattice alignment increases the hole mobility and decreases the performance fluctuations of devices. The results confirm that the out-of-plane lattice alignment significantly impacts the performance of the devices and the reproducibility of the solution-processed TIPS-PEN OFETs. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of Cu(NO3)2 and 2-isopropylimidazole (Hipim) in different solvents/templates gave three supramolecular isomers: α-[Cu(ipim)] (1), β-[Cu(ipim)] (2), and γ-[Cu(ipim)]·1/3C6H6 (3). Single-crystal X-ray diffraction analyses showed that 1, 2, and 3 are parallel-packed wavy chains, triple-stranded helices, and cubic-orthogonal-packed helical chains consisting of alternatively interconnected two-coordinated Cu(I) ions and ipim- ligands. Because of the different intermolecular interactions, 1, 2, and 3 show different phosphorescence properties with emission maxima at 555, 540, and 530 nm, respectively. More interestingly, [Cu(ipim)] can melt at high temperature without decomposition. Compounds 1 and 2 melt above 185 and 146 °C, respectively; this liquid solidifies below 117 °C to form 1 again. However, 3 loses the benzene guest molecules above 90 °C and transforms to 1 in a crystal-to-crystal manner. [ABSTRACT FROM AUTHOR]

Using a bis-triazolate ligand and tetrahedral Zn(II) ion, we synthesized a flexible porous coordination polymer functionalized with pairs of uncoordinated triazolate N-donors that can be used as guest chelating sites to give very high CO2 adsorption enthalpy and CO2/N2 selectivity. The dynamic CO2 sorption behavior could be monitored well by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

The reaction of commercially available 3-animo-1,2,4-triazole (Hatz) and Zn(OH)2 at room temperature produced a porous zeolite-like metal azolate framework, [Zn(atz)2] (MAF-66). Single-crystal X-ray diffraction studies of MAF-66 showed that atz- served as an imidazolate-type ligand, linking tetrahedral ZnII ions to form a noninterpenetrated dia framework, which contains a narrow, three-dimensional intersecting channel system (void = 49.8%) functionalized by amino groups and uncoordinated triazolate N atoms on the pore surface. Gas-sorption measurements of MAF-66 revealed high CO2 uptakes (27.6/19.4 wt % at 273/298 K and 1 atm) and high Henry's law CO2/N2 selectivity (403/225 at 273/298 K). The host-guest interactions between CO2 and the pore surface were also studied by in situ IR absorption spectroscopy and powder X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of metal salts, benzenedicarboxylic acids, and 4,4′-azopyridine (azpy) in different conditions produced four coordination polymers, namely, [Zn3(bdc)3(bphy)3]·2DMF·10H2O (3; H2bdc = 1,4-benzenedicarboxylic acid, bphy = 1,2-bis(4-pyridyl)hydrazine, and DMF = N,N-dimethylformamide), [Ni(bdc)(bphy)]·DMF·3.5H2O (4), [Zn(nipa)(bphy)]·EtOH (5; H2nipa = 5-nitroisophthalic acid), and [CoBr(bdc)0.5(bphy)]·2DMA·H2O (6; DMA = N,N-dimethylacetamide), in which the azpy ligand was in situ reduced. Structural determination reveals that 3-5 consist of the same metal/ligand ratio and similar coordination modes, as well as similar two-dimensional square-grid networks, but differ from their packing/interpenetration modes. 3 consists of alternately arranged single layers and interweaved double layers. Single layers in 4 directly stack in an offset fashion, while 5 is constructed of interdigitated double layers. 6 is a one-dimensional ladderlike structure, which could be regarded as that half of the bridging benzenedicarboxylate ligands in 3-5 are replaced by monodentate bromide ions. Interestingly, the crystal structures of these low-dimensional coordination polymers contain considerable solvent-accessible voids. Thermogravimetric curves, powder X-ray diffraction, and gas sorption experiments were used to study the potential porosity of these structures, which indicated that they can all reversibly desorb and adsorb solvent molecules. In particular, 4 showed gated sorption behavior and high CO2/CH4 selectivity because of its flexible structure. [ABSTRACT FROM AUTHOR]

Self-assembly of silver(I) ion with 3-alkyl-1,2,4-triazoles in different solvents yielded four new metal azolate frameworks (MAFs), namely, [Ag(mtz)] (1, Hmtz = 3-methyl-1,2,4-triazole), [Ag(etz)] (2, Hetz = 3-ethyl-1,2,4-triazole), [Ag4(etz)4]·H2O (3·H2O), and [Ag4(ptz)4] (4, Hptz = 3-propyl-1,2,4-triazole). Single-crystal X-ray diffraction revealed that Ag(I) ions and triazolates in these MAFs are all three-coordinated to give rare 3-connected framework topologies. Although 1and 2possess the same uniform (10,3)-d (utp) topology, variation of the alkyl groups renders substantially different coordination structures. On the other hand, 3·H2O and 4, also bearing different alkyl substituents, are isomorphours, and can be simplified as the same uninodal sqc5603 topology (point and vertex symbols are 82.10 and 8.82.12, respectively). Due to the relatively short alkyl length, the coordination framework of 3·H2O contains one-dimensional narrow channels. According to thermogravimetry and single-crystal X-ray diffraction, 3·H2O can be dehydrated without framework collapse. Although guest-free 3does not adsorb N2at 77 K, 3·H2O can undergo guest exchange, and 3can adsorb solvent vapor, to give CH2Cl2- and CH3CN-included crystals. Comparing the single-crystal structures of 3·H2O, 3, 3·CH2Cl2, and 3·CH3CN reveals the framework flexibility of 3. These materials also show interesting structure- and guest-dependent photoluminescent properties. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of equimolar zinc acetate, lithium acetate, and 1,3,5-benzenelricarboxylic acid (H3btc) in different mixed solvents yielded isostnictural three-dimensional frameworks [UZn(btc)()) - IG leG and IG denote coordinated and lattice guests, respectively; cG=(nmp)0.5(H2O)0.5, IG=(EtOH)0.5 (1a); cG=H2O, IG= EtOH (1b); nmp=N-methyl-2-pyrrolidone] with one-dimensional channels occupied by guest molecules and solvent-coordinated, extrusive Li+ ions. Thermogravimetry analyses and powder X-ray diffraction measurements revealed that both la and lb can lose all lattice and coordinated guests to torn', a desolvaled phase [LiZn(btc)] (MCF-27, 1) and almost retains the original framework structure. Gas adsorption measurements on 1 confirmed its permanent porosity but suggested a structural transformation horn 1a/1b 101.11 is noteworthy that only la can undergo a single-ctystal 10 single-crystal (SCSC) transformation into 1 upon desolvation. The crystal structure of 1 revealed that Ihe Li+ ions were retracted into the channel walls via complementary coordination to the carboxylate oxygen atoms in the framework rather than being exposed on the pore surface. Single-crystal X-ray diffraction analyses were also performed for N2- and CO2-loaded samples of 1, revealing that the framework remained unchanged when the gases were adsorbed. Although the gas molecules could not be modeled, the residue electrons inside the channels demonstrated that the retracted Li+ ions still behave as the primary interacting site for CO2 molecules. Nevertheless, solvent molecules such as H2O can readily compete with the framework oxygen atom to retrieve the extrusive Li+ ions, accompanying the reverse structural transformation, i.e., from 1 to 1a/1b. [ABSTRACT FROM AUTHOR]

The anionic syn-/anti-[Fe(μ-SEt)(NO)2]2- (2a) were synthesized and characterized by IR, UV-vis, EPR, and X-ray diffraction. The geometry of the [Fe(μ-S)2Fe] core is rearranged in going from [{Fe(NO)2}9-{Fe(NO)2}9J Roussin's red ester [Fe(μ-SEt)(NO)2]2 (la) (Feߪ Fe distance of 2.7080(5) Å) to the [{Fe(NO)2}9-{Fe(NO)2}10] complex 2a (Fe ߪ Fe distance of 2.8413(6) Å) to minimize the degree of Fe ߪ Fe interaction to stabilize complex 2a. On the basis of X-ray absorption (Fe K- and L-edge), EPR and SQUID, complex 2a is best described as the anionic [{Fe(NO)2}9-{Fe(NO)2}10] Roussin's red ester with the fully delocalized mixed-valence core. The complete bridged- thiolate cleavage yielded DNIC [(EtS)2Fe(NO)2]- (3a) in the reaction of 2 equiv of [EtS]- and complex 1a, whereas reaction of 2 equiv of [tBuS]- with [Fe(μ-StBu)(NO)2]2 (1b) gave DNIC [(tBuS)2Fe(NO)2]- (3b) and the anionic Roussin's red ester [Fe(μ-StBu)(NO)2]2- (2b) through bridged-thiolate cleavage in combination with reduction. In contrast to the inertness of DNIC 3b toward complex 1b, nucleophile DNIC 3a induces the reduction of complex la to produce the anionic Roussin's red ester 2a. Interestingly, dissolution of complex 3a in MeOH at 298 K finally led to the formation of a mixture of complexes 2a and 3a, in contrast to the dynamic equilibrium of complexes 3b and lb observed in dissolution of complex 3b in MeOH. These results illustrate the aspect of how the steric structures of nucleophiles ([EtS]- vs [tBuS]- and [(EtS)2Fe(NO)2]- vs [(tBuS)2Fe(NO)2]-) function to determine the reaction products. [ABSTRACT FROM AUTHOR]

The neutral trinuclear iron-thiolate-nitrosyl, [(ON)Fe(μ-S,S-C6H4)]3 (1), and its oxidation product, [(ON)Fe(μ-S,S-C6H4)]3[PF6] (2), were synthesized and characterized by IR, X-ray diffraction, X-ray absorption, electron paramagnetic resonance (EPA), and magnetic measurement. The five-coordinated, square pyramidal geometry around each iron atom in complex 1 remains intact when complex 1 is oxidized to yield complex 2. Magnetic measurements and EPA results show that there is only one unpaired electron in complex 1 (Stotal = 1/2) and no unpaired electron (Stotal = 0) in 2. The detailed geometric comparisons between complexes 1 and 2 provide understanding of the role that the unpaired electron plays in the chemical bonding of this trinuclear complex. Significant shortening of the Fe-Fe, Fe-N, and Fe-S distances around Fe(1) is observed when complex 1 is oxidized to 2. This result implicates that the removal of the unpaired electron does induce the strengthening of the Fe-Fe, Fe-N, and Fe-S bonds in the Fe(1) fragment. A significant shift of the νNO stretching frequency from 1751 cm-1 (1) to 1821, 1857 cm-1 (2) (KBr) also indicates the strengthening of the N-a bonds in complex 2. The EPA, X-ray absorption, magnetic measurements, and molecular orbital calculations lead to the conclusion that the unpaired electron in complex 1 is mainly allocated in the Fe(1) fragment and is best described as {Fe(1)NO}7, so that the unpaired electron is delocalized between Fe and NO via d-π* orbital interaction; some contributions from [Fe(2)NO] and [Fe(3)NO] as well as the thiolates associated with Fe (1) are also realized. According to MO calculations, the spin density of complex 1 is predominately located at the Fe atoms with 0.60, -0.15, and 0.25 at Fe(1), Fe(2), and Fe(3), respectively. [ABSTRACT FROM AUTHOR]

Two new isostructural complexes [M(H2biim)3][M(btc)(Hbiim)]•2H2O (M = Co, (1); M = Ni, (2)) (btc = 1,3,5-benzenetricarboxylate; H2biim = 2,2′-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. They present a unique structure consisting of two distinct units: the monomeric cations [M(H2biim)3]2+ and the two-dimensional (2D) anionic polymer [M(Hbiim)(btc)]2-. In the anionic moiety, the Hbiim monoanion is simultaneously coordinated to one metal atom in a bidentate mode and further to another metal atom in a monodentate mode. The imidazolate groups bridge the two adjacent metal ions into a helical chain which is further arranged in left- and right-handed manners. These chains are bridged by btc ligands into a 2D brick wall structure. The most interesting aspect is that the [M(H2biim)3]2+ cations act as pillars and link the anionic layers via robust heteromeric hydrogen-bonded synthons R²2(9) and R¹2(7) formed by the uncoordinated oxygen atoms of carboxylate groups and the H2biim ligands, resulting in a microporous metal-organic framework with one-dimensional (1D) channels (ca. 11.85 Å ⊗ 11.85 Å for 1 and 11.43 Å ⊗ 11.43 Å for 2). Magnetic properties of these two complexes have also been studied in the temperature range of 2–300 K, and their magnetic susceptibilities obey the Curie-Weiss law in the temperature range of 20–300 K (for 1) and 2–300 K (for 2), respectively, showing anti-ferromagnetic coupling through imidazolate bridging. Taking into consideration the Heisenberg infinite chain model as well as the possibility of chain-to-chain and chain-to-cation interactions, the anti-ferromagnetic exchange of 2 is analyzed via a correction for the molecular field, giving the values of gcat = 2.296, gNi = 2.564, J = -13.30 cm-1, and zJ′ = -0.017 cm-1. The microporous frameworks are stable at ca. 350 °C. They do not collapse after removal of the guest water molecules in the channels, and they adsorb methanol molecules selectively. [ABSTRACT FROM AUTHOR]