Aliphatic β‐Nitroalcohols for Therapeutic Corneoscleral Cross‐Linking: Chemical Stability Studies Using 1H‐NMR Spectroscopy

Recent studies suggest that aliphatic β‐nitro alcohols may represent a useful class of compounds for use as in vivo therapeutic corneoscleral cross‐linking agents with higher order nitroalcohols (HONAs) showing enhanced efficacy over the mono‐nitroalcohols. The current study was undertaken in order to evaluate the chemical stability of these compounds during storage conditions. Two mono‐nitroalcohols (2‐nitroethanol=2ne and 2‐nitro‐1‐propanol=2nprop) and two HONAs, a nitrodiol (2‐methyl‐2‐nitro‐1,3‐propanediol=MNPD), and a nitrotriol (2‐hydroxymethyl‐2‐nitro‐1,3‐propanediol=HNPD) were monitored for chemical stability by ¹H‐NMR for up to 7 months. Each compound was studied at two concentrations (1% and 10%) either in unbuffered H₂O or 0.2 m NaH₂PO₄/Na₂HPO₄ (pH=5), and at 0°C and room temperature (RT) for a total of eight conditions for each compound. The ¹H‐NMR spectra for the starting material were compared to subsequent spectra. Under all four of the conditions studied, both the nitrodiol (MNPD) and nitrotriol (HNPD) were stable for the duration of 7 months. 2nprop became unstable under all conditions at 3 months. 2ne was the most unstable of all the compounds tested. HONAs exhibit excellent chemical stability under long‐term storage conditions. In contrast, the nitromonols tested are significantly less stable. These findings are relevant to the translation of this technology into clinical use.     

Demonstration of the Heterolytic O?O Bond Cleavage of Putative Nonheme Iron(II)?OOH(R) Complexes for Fenton and Enzymatic Reactions

One‐electron reduction of mononuclear nonheme iron(III) hydroperoxo (Fe^III OOH) and iron(III) alkylperoxo (Fe^III OOR) complexes by ferrocene (Fc) derivatives resulted in the formation of the corresponding iron(IV) oxo complexes. The conversion rates were dependent on the concentration and oxidation potentials of the electron donors, thus indicating that the reduction of the iron(III) (hydro/alkyl)peroxo complexes to their one‐electron reduced iron(II) (hydro/alkyl)peroxo species is the rate‐determining step, followed by the heterolytic O O bond cleavage of the putative iron(II) (hydro/alkyl)peroxo species to give the iron(IV) oxo complexes. Product analysis supported the heterolytic O O bond‐cleavage mechanism. The present results provide the first example showing the one‐electron reduction of iron(III) (hydro/alkyl)peroxo complexes and the heterolytic O O bond cleavage of iron(II) (hydro/alkyl)peroxo species to form iron(IV) oxo intermediates which occur in nonheme iron enzymatic and Fenton reactions.     

Observation of high coherence in Josephson junction qubits measured in a three-dimensional circuit QED architecture

Superconducting quantum circuits based on Josephson junctions have made rapid progress in demonstrating quantum behavior and scalability. However, the future prospects ultimately depend upon the intrinsic coherence of Josephson junctions, and whether superconducting qubits can be adequately isolated from their environment. We introduce a new architecture for superconducting quantum circuits employing a three-dimensional resonator that suppresses qubit decoherence while maintaining sufficient coupling to the control signal. With the new architecture, we demonstrate that Josephson junction qubits are highly coherent, with T2 ～ 10 to 20 μs without the use of spin echo, and highly stable, showing no evidence for 1/f critical current noise. These results suggest that the overall quality of Josephson junctions in these qubits will allow error rates of a few 10(-4), approaching the error correction threshold.     

Overstretching DNA at 65 pN does not require peeling from free ends or nicks

DNA exhibits a remarkable mechanical transition where its extension increases by 70% at 65 pN. Notwithstanding more than a decade of experimental and theoretical studies, there remains a significant debate on the nature of overstretched DNA. We developed a topologically closed but rotationally unconstrained DNA assay, which contains no nicks or free ends. DNA in this assay exhibited the canonical overstretching transition at 65 pN but without hysteresis upon retraction (v(stage) = 5 μm/s). Introduction of a controlled nick led to hysteresis in the force-extension curve. Moreover, the degree of hysteresis increased with the number of nicks. Hence, the generation of single-stranded DNA from free ends or nicks is not an obligatory step in overstretching DNA, but rather a consequence.     

Assessment of the Arsenic Removal From Water Using Lanthanum Ferrite

The catalytic performance of a perovskite-type lanthanum ferrite LaFeO₃ to remove arsenic from water has been investigates for the first time. LaFeO₃ was prepared by citrate auto-combustion of dry gel obtained from a solution of the corresponding nitrates poured into citric acid solution. Kinetic studies were performed in the dark with As(V) and in the dark and under UV-C irradiation at pH 6–7 with As(III) (both 1 mg L⁻¹), and As : Fe molar ratios (MR) of 1 : 10 and 1 : 100 using the LaFeO₃ catalyst. As(V) was removed from solution after 60 min in the dark in 7 % and in 47 % for MR=1 : 10 and MR=1 : 100, respectively, indicating the importance of the amount of the iron material on the removal. Oxidation of As(III) in the dark was negligible after 60 min in contact with the solid sample, but complete removal of As(III) was observed within 60 min of irradiation at 254 nm, due to As(III) photooxidation to As(V) and to As(III) sorption to a minor extent. Morphological and microstructural studies of the catalyst complement the catalytic testing. This work demonstrates that LaFeO₃ can be used for the removal of As(III) from highly arsenic contaminated water.     

A hybrid consisting of coordination polymer and noncovalent organic networks: a highly ordered 2-D phenol network assembled by edge-to-face pi-pi interactions

A 2-D metal-organic open framework having 1-D channels, [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).18H(2)O (1), was constructed by the self-assembly of the Cu(II) complex of hexaazamacrocycle A (A = C(10)H(26)N(6)) with sodium 1,3,5-benzenetricarboxylate (BTC(3)(-)) in DMSO-H(2)O solution. 1 crystallizes in the trigonal space group P with a = b = 17.705(1) A, c = 6.940(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 1884.0(3) A(3), Z = 1, and rho(calcd) = 1.428 g cm(-3). The X-ray crystal structure of 1 indicates that each Cu(II) macrocyclic unit binds two BTC(3-) ions in a trans position and each BTC(3-) ion coordinates three Cu(II) macrocyclic complexes to form 2-D coordination polymer layers with honeycomb cavities (effective size 8.1 A), and the layers are packed to generate 1-D channels perpendicularly to the 2-D layers. Solid 1 binds guest molecules such as MeOH, EtOH, and PhOH with different binding constant and capacity. By the treatment of 1 with aqueous solution of phenol, a hybrid solid [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).9PhOH.6H(2)O (2) was assembled. 2 crystallizes in the trigonal R3 space group with a = b = 20.461(1) A, c = 24.159(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 8759.2(7) A(3), Z = 3, and rho(calcd) = 1.280 g cm(-3). In 2, highly ordered 2-D noncovalent phenol layers are formed by the edge-to-face pi-pi interactions between the phenol molecules and are alternately packed with the coordination polymer layers in the crystal lattice.     

Well‐Arranged and Confined Incorporation of PdCo Nanoparticles within a Hollow and Porous Metal–Organic Framework for Superior Catalytic Activity

A convenient method for the confined incorporation of highly active bimetallic PdCo nanocatalysts within a hollow and porous metal–organic framework (MOF) support is presented. Several chemical conversions occur simultaneously during the one‐step low temperature pyrolysis of well‐designed polystyrene@ZIF‐67/Pd²⁺ core–shell microspheres, where ZIF (zeolitic imidazolate framework) is a subclass of MOF: the polystyrene core is removed, resulting in a beneficial hollow and porous ZIF support; the ZIF‐67 shell acts as a well‐defined porous support and as a felicitous Co²⁺ supplier for metal nanoparticle formation; and Pd²⁺ and Co²⁺ are reduced to form catalytically active bimetallic PdCo nanoparticles in the well‐defined micropores, inducing the confined growth of PdCo nanoparticles with excellent dispersity.     

Encapsulation of Water-Soluble Dye in Spherical Sol-Gel Silica Matrices

The water-soluble, Lithol rubine B, dye was encapsulated into silica microspheres matrices. Encapsulation has been carried out by sol-gel process of W/O microemulsions formed from sodium silicate and dye aqueous solution in cyclohexane medium. The average particle size could be tailored from 1–10 m, depending on the processing parameter such as homogenizing speed in the formation of W/O emulsion, the weight ratio of water to oil, and concentration of sodium silicate solution, etc. The pore size of dye-doped silica microspheres was measured by nitrogen adsorption-desorption isotherms. The leaching behavior of dye entrapped in silica matrices was investigated by UV/VIS and UV diffuse reflectance spectroscopy for the extract and solid powders after immersion for 24 h in water. The doping of GPTS (3-glycidoxypropyltrimethoxysilane) in sodium silicate and dye mixture solution greatly enhanced the stability against leaching of the dye. It was ascribed that GPTS serves simultaneously as an intermediate for the chemical bonding between the dye and silica, and as an agent for the formation of hybrid sol responsible for the shrinkage of pore size.     

(2)H MAS NMR studies of the manganese dioxide tunnel structures and hydroxides used as cathode materials in primary batteries

Variable-temperature (2)H MAS NMR spectroscopy was used to investigate the local environments and mobility of deuterons in the manganese dioxide tunnel structures. Five systems were investigated: electrolytic manganese dioxide (EMD), the model compounds groutite and manganite, and deuterium intercalated ramsdellite and pyrolusite. Ruetschi deuterons, located in the cation vacancy sites in EMD, were detected by NMR and give rise to a resonance at 150 ppm at room temperature. These deuterons are rigid on the (2)H MAS NMR time scale (i.e., the correlation time for motion, tau(c), is >10(-3) s) at room temperature, but start to become mobile above 150 degrees C. No Coleman protons (in the so-called 1 x 1 and 1 x 2 tunnels in EMD) were observed. Much larger (2)H NMR hyperfine shifts of approximately 300 and approximately 415 ppm were observed for the deuterons in the tunnel structures of manganite and groutite, which could be explained by considering the different bonding arrangements for deuterons in the 1 x 1 and 1 x 2 tunnels. The smaller shift of the EMD deuterons was primarily ascribed to the smaller number of manganese ions in the deuterium local coordination sphere. Experiments performed as a function of intercalation level for ramsdellite suggest that the 1 x 1 tunnels are more readily intercalated in highly defective structures. The almost identical shifts seen as a function of intercalation level for deuterons in both 1 x 1 and 1 x 2 tunnels are consistent with the localization of the e(g) electrons near the intercalated deuterium atoms. A Curie-Weiss-like temperature dependence for the hyperfine shifts of EMD and groutite was observed with temperature, but very little change in the shift of the manganite deuterons was observed, consistent with the strong antiferromagnetic correlations that exist above the Néel temperature for this compound. These different temperature dependences could be used to identify manganite-like domains within the sample of groutite, which could not be detected by X-ray diffraction.     

Carbon Nanotubes as a Ligand in Cp2ZrCl2‐Based Ethylene Polymerization

Summary: We report a simple method for tuning catalytic property of a metallocene‐based catalyst, Cp₂ZrCl₂, for ethylene polymerization by the direct adsorption of Cp₂ZrCl₂ onto multi‐walled carbon nanotubes (MWCNTs). The direct interactions between MWCNTs and the Cp rings of Cp₂ZrCl₂ controlled the polymerization behaviors, and we could generate polyethylene with an extremely high molecular weight ( = 1 000 000) at 30 °C and under 1 atm of ethylene gas.

Preparation of Cp₂ZrCl₂‐MWCNT.