bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhancing the Water Stability of Al‐MIL‐101‐NH2 via Postsynthetic Modification
Authors: Wittmann Thomas , Siegel Renée , Reimer Nele , Milius Wolfgang , Stock Norbert , Senker Jürgen 
Published: October 2014

AbstractThe resistance of metal–organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al‐MIL‐101‐NH2 by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long‐term stability of Al‐MIL‐101‐URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al‐MIL‐101‐URPh decomposed at least 12‐times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N2 and H2O sorption measurements, powder X‐ray diffraction, thermogravimetric and chemical analysis as well as solid‐state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m2 g−1 for Al‐MIL‐101‐URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity‐dependent uptake of Al‐MIL‐101‐URPh is slowed and occurs at higher relative humidity values. In combination with 1H‐27Al D‐HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking.
Carboranes Tuning the Phosphorescence of Iridium Tetrazolate Complexes
Authors: Shi Chao , Tu Deshuang , Yu Qi , Liang Hua , Liu Yahong , Li Zhihong , Yan Hong , Zhao Qiang , Huang Wei 
Published: October 2014

AbstractNew iridium tetrazolate complexes containing o‐, m‐, or p‐carboranyl substitution in different positions of a phenylpyridine ligand have been prepared. The carborane isomers and the effect of their substitution position in the tuning of optical properties have been examined. The neutral complexes with the carboranyl substituent on the phenyl ring in meta position relative to the metal exhibit redshifted emission bands in contrast to blueshifts for those with carboranyl in para position. All cationic complexes display evidently blueshifted dual‐peak emission compared with the carborane‐free complex (c‐TZ) with a broad single‐peak emission. Introduction of carborane leads to a blueshift over 70 nm relative to c‐TZ. Carboranes also significantly improve phosphorescence efficiency (ΦP) and lifetime (τ), that is, ΦP=0.64 versus 0.21 (c‐TZ) and τ=880 ns versus 241 ns (c‐TZ). The unique hydrophilic nido‐carborane‐based IrIII complex nido‐o‐1 shows the largest phosphorescence efficiency (abs ΦP=0.57) among known water‐soluble iridium complexes, long emission lifetime (τ=4.38 μs), as well as varying emission efficiency and lifetime with O2 content in aqueous solution. Therefore, nido‐o‐1 has been used as an excellent oxygen‐sensitive phosphor for intracellular O2 sensing and hypoxia imaging.
A Combined Experimental and Theoretical Study on the Isomers of 2,3,4,5‐Tetracarba‐nido‐Hexaborane(6) Derivatives and Their Photophysical Properties
Authors: Braunschweig Holger , Ghosh Sundargopal , Jimenez‐Halla J. Oscar C. , Klein Johannes H. , Lambert Christoph , Radacki Krzysztof , Steffen Andreas , Vargas Alfredo , Wahler Johannes 
Published: October 2014

AbstractBuilding upon our ongoing studies on the high‐yield synthetic route to 2,3,4,5‐tetracarba‐1,6‐nido hexaborane derivative 5, we continue to explore the chemistry of this system to isolate a range of perphenylated C4B2‐type carborane isomers. As a result, the photolysis of 5 for an elongated period yielded 6, which exhibits an intense luminescence upon excitation with a UV lamp (λex=366 nm). In contrast, the conversion of 5 under thermal conditions (microwave heating) generated the isomer 7, which does not show any luminescence. The structural disparity among the three isomers 5–7 is the position of the butadiene moiety with respect to the C4B2‐carborane cage as deduced from single‐crystal X‐ray diffraction analyses. In an attempt to generate the classical structural motif of 5, an equimolar amount of KOtBu was added to a THF solution of 5, which immediately provided the boratacyclopentadiene derivative 8 in good yield. The observed rearrangement reactions were further investigated by quantum chemical calculations to suggest a plausible reaction pathway. According to the DFT calculations, the energetically favored reaction mechanism most likely involves tricyclic transition states and classical intermediate structures. In addition, the fluorescence emission properties of 6 were investigated in solution as well as in the solid state.
Enantioselective Synthesis of Chiral Isotopomers of 1‐Alkanols by a ZACA–Cu‐Catalyzed Cross‐Coupling Protocol
Authors: Xu Shiqing , Oda Akimichi , Negishi Ei‐ichi 
Published: October 2014

AbstractChiral compounds arising from the replacement of hydrogen atoms by deuterium are very important in organic chemistry and biochemistry. Some of these chiral compounds have a non‐measurable specific rotation, owing to very small differences between the isotopomeric groups, and exhibit cryptochirality. This particular class of compounds is difficult to synthesize and characterize. Herein, we present a catalytic and highly enantioselective conversion of terminal alkenes to various β and more remote chiral isotopomers of 1‐alkanols, with ≥99 % enantiomeric excess (ee), by the Zr‐catalyzed asymmetric carboalumination of alkenes (ZACA) and Cu‐catalyzed cross‐coupling reactions. ZACA‐in situ iodinolysis of allyl alcohol and ZACA‐in situ oxidation of TBS‐protected ω‐alkene‐1‐ols protocols were applied to the synthesis of both (R)‐ and (S)‐difunctional intermediates with 80–90 % ee. These intermediates were readily purified to provide enantiomerically pure (≥99 % ee) compounds by lipase‐catalyzed acetylation. These functionally rich intermediates serve as very useful synthons for the construction of various chiral isotopomers of 1‐alkanols in excellent enantiomeric purity (≥99 % ee) by introducing deuterium‐labeled groups by Cu‐catalyzed cross‐coupling reactions without epimerization.
Copper/Palladium‐Cocatalyzed Aerobic Synthesis of Bisaryl Ketones from Olefins via C‐C Double Bonds Cleavage
Authors: Gu Lijun , Liu Jiyan , Zhang Hongtao 
Published: November 2014

AbstractA novel palladium/copper‐catalyzed aerobic synthesis of bisaryl ketones from 1,2‐diarylalkenes via C‐C double bonds cleavage has been described. This reaction constitutes a new transformation from 1,2‐diarylalkenes into bisaryl ketones, providing a unifying, simple and environmentally friendly complement to the available methods.
Stochastic dynamic models and Chebyshev splines
Authors: Fan Ruzong , Zhu Bin , Wang Yuedong 
Published: November 2014

AbstractIn this article, we establish a connection between a stochastic dynamic model (SDM) driven by a linear stochastic differential equation (SDE) and a Chebyshev spline, which enables researchers to borrow strength across fields both theoretically and numerically. We construct a differential operator for the penalty function and develop a reproducing kernel Hilbert space (RKHS) induced by the SDM and the Chebyshev spline. The general form of the linear SDE allows us to extend the well‐known connection between an integrated Brownian motion and a polynomial spline to a connection between more complex diffusion processes and Chebyshev splines. One interesting special case is connection between an integrated Ornstein–Uhlenbeck process and an exponential spline. We use two real data sets to illustrate the integrated Ornstein–Uhlenbeck process model and exponential spline model and show their estimates are almost identical.The Canadian Journal of Statistics42: 610–634; 2014 © 2014 Statistical Society of Canada
Synthetic 1‐Deoxynojirimycin N‐Substituted Peptides Offer Prolonged Disruption to N‐Linked Glycan Processing
Authors: Aguilar Aimé López , Escribano Jaime , Wentworth Paul , Butters Terry D. 
Published: October 2014

AbstractA panel of 1‐deoxynojirimycin (DNJ) N‐linked peptides were synthesized. Their IC50 values were measured in vitro against α‐glucosidases I and II and were found to be in the micromolar range for both isozymes, and better than that of the iminosugar NB‐DNJ (miglustat, 3) against α‐glucosidase II. Cell‐based studies revealed that although the free iminosugar 3 is most effective at disrupting N‐linked glycan processing for short‐term incubations (one day), when the cell‐based studies were extended to three days, the DNJ N‐linked tetrapeptide KDEL, which is an endoplasmic reticulum (ER)‐retaining sequence, performed far better than 3. In low inhibitor washout studies, NB‐DNJ inhibition was decreased to zero after 24 h, but DNJ–KDEL retained 13 % activity. This method offers a general approach for targeting drugs to the ER and prolonging their activity. Moreover, it is modular, so as new iminosugars of increased potency are discovered, they can be added to this template for targeting.
Analysis of thyroid malignant pathologic findings identified during 3 rounds of screening (1997‐2008) of a cohort of children and adolescents from Belarus exposed to radioiodines after the Chernobyl accident
Authors: Zablotska Lydia B. , Nadyrov Eldar A. , Rozhko Alexander V. , Gong Zhihong , Polyanskaya Olga N. , McConnell Robert J. , O'Kane Patrick , Brenner Alina V. , Little Mark P , Ostroumova Evgenia , Bouville Andre , Drozdovitch Vladimir , Minenko Viktor , Demidchik Yuri , Nerovnya Alexander , Yauseyenka Vassilina , Savasteeva Irina , Nikonovich Sergey , Mabuchi Kiyohiko , Hatch Maureen 
Published: October 2014

BACKGROUNDRecent studies of children and adolescents who were exposed to radioactive iodine‐131 (I‐131) after the 1986 Chernobyl nuclear accident in Ukraine exhibited a significant dose‐related increase in the risk of thyroid cancer, but the association of radiation doses with tumor histologic and morphologic features is not clear.METHODSA cohort of 11,664 individuals in Belarus who were aged ≤18 years at the time of the accident underwent 3 cycles of thyroid screening during 1997 to 2008. I‐131 thyroid doses were estimated from individual thyroid activity measurements taken within 2 months after the accident and from dosimetric questionnaire data. Demographic, clinical, and tumor pathologic characteristics of the patients with thyroid cancer were analyzed using 1‐way analysis of variance, chi‐square tests or Fisher exact tests, and logistic regression.RESULTSIn total, 158 thyroid cancers were identified as a result of screening. The majority of patients had T1a and T1b tumors (93.7%), with many positive regional lymph nodes (N1; 60.6%) but few distant metastases (M1; <1%). Higher I‐131 doses were associated with higher frequency of solid and diffuse sclerosing variants of thyroid cancer (P < .01) and histologic features of cancer aggressiveness, such as lymphatic vessel invasion, intrathyroidal infiltration, and multifocality (all P < .03). Latency was not correlated with radiation dose. Fifty‐two patients with self‐reported thyroid cancers which were diagnosed before 1997 were younger at the time of the accident and had a higher percentage of solid variant cancers compared with patients who had screening‐detected thyroid cancers (all P < .0001).CONCLUSIONSI‐131 thyroid radiation doses were associated with a significantly greater frequency of solid and diffuse sclerosing variants of thyroid cancer and various features of tumor aggressiveness. Cancer 2015;121:457–466. © 2014 American Cancer Society.
Dynamic Potential‐Dependent Electron Transport Pathway Shifts in Anode Biofilms of Geobacter sulfurreducens
Authors: Yoho Rachel A. , Popat Sudeep C. , Torres César I. 
Published: October 2014

AbstractBiofilms of the anode‐respiring bacterium Geobacter sulfurreducens (G. sulfurreducens) demonstrate dynamic potential‐dependent changes between two electron transport pathways that are used selectively depending on the anode potential. Electrochemical impedance spectroscopy (EIS) measurements suggest that these pathways (both n=1), with midpoint potentials of −0.155 (±0.005) and −0.095 (±0.003) V versus standard hydrogen electrode, are not additive within the biofilm, but are preferentially used depending on the anode potential. Potential step voltammetry and cyclic voltammetry (CV) confirmed rapid changes between the two pathways in minutes when the anode potential is changed. We confirm that the electrochemical response observed in a slow‐scan‐rate CV (∼1 mV s−1) is often composed of at least the two pathways characterized. Thus, beyond understanding the electron transport pathways in G. sulfurreducens, this study also has implications on the interpretation of previously collected and future potential‐dependent datasets.
3 D Single‐Walled Carbon Nanotube/Graphene Aerogels as Pt‐Free Transparent Counter Electrodes for High Efficiency Dye‐Sensitized Solar Cells
Authors: Ma Jie , Li Cheng , Yu Fei , Chen Junhong 
Published: October 2014

Abstract3D single‐walled carbon nanotube (SWCNT)/graphene aerogel (NGS) was synthesized and used as an alternative to platinized fluorine‐doped tin oxide (FTO) in dye‐sensitized solar cells (DSSCs). An island‐like structure formed on the FTO using the spin‐coating method, leading to a transmittance (49.86 % at 671 nm). The resulting NGS‐based counter electrodes (CEs) exhibited excellent power conversion efficiency (PCE) (8.31 %) compared to Pt (7.56 %). Surprisingly, PCE increased to 9.64 % under assisted by a mirror; The excellent performance of DSSCs can be attributed to the high electrical conductivity and good electrocatalytic activity induced by the SWCNTs and the excellent catalytic properties of graphene, coupled with the 3D structure with a larger surface area and good surface hydrophilicity for increased electrolyte‐electrode interactions and electrolyte/reactant diffusion. Hence, our results demonstrate that 3D‐NGS materials have considerable potential for DSSC‐related applications and merit further investigation.
Three‐dimensional image cytometer based on widefield structured light microscopy and high‐speed remote depth scanning
Authors: Choi Heejin , Wadduwage Dushan N. , Tu Ting Yuan , Matsudaira Paul , So Peter T. C. 
Published: October 2014

AbstractA high throughput 3D image cytometer have been developed that improves imaging speed by an order of magnitude over current technologies. This imaging speed improvement was realized by combining several key components. First, a depth‐resolved image can be rapidly generated using a structured light reconstruction algorithm that requires only two wide field images, one with uniform illumination and the other with structured illumination. Second, depth scanning is implemented using the high speed remote depth scanning. Finally, the large field of view, high NA objective lens and the high pixelation, high frame rate sCMOS camera enable high resolution, high sensitivity imaging of a large cell population. This system can image at 800 cell/sec in 3D at submicron resolution corresponding to imaging 1 million cells in 20 min. The statistical accuracy of this instrument is verified by quantitatively measuring rare cell populations with ratio ranging from 1:1 to 1:105. © 2014 International Society for Advancement of Cytometry
Shrub spatial organization and partitioning of evaporation and transpiration in arid environments
Authors: Zhu Jianting , Sun Dongmin , Young Michael H. , Caldwell Todd G. , Pan Feng 
Published: October 2014

AbstractEvapotranspiration (ET) dominates water fluxes in arid and semiarid ecosystems. The partitioning of ET into transpiration (T) and evaporation (E) has drawn increasing attention, particularly with respect to quantifying the control of shrub cover on water budget studies. The main objective of this study was to simulate the effects of shrub coverage spatial patterns on water partitioning into T and E and its relation to the simulation cell sizes. Correlation lengths of spatially distributed shrub cover in fine resolution grid cells were used to distinguish spatial patterns (i.e. patchiness) of shrub distributions. We then aggregated the fine resolution grid cells into larger cells of various hierarchies, calculated the potential T of each large cell as a portion of potential ET in the aggregated cell, and simulated the partitioning of actual ET into T and E. Results illustrated that simulated T increases with aggregated cell size, while E rate and total E do not change significantly (i.e. T/ET increases with aggregated cell size). The spatial distribution of shrub pattern influences the partitioning of ET: T increases with decreasing correlation length of shrub spatial pattern. Significant differences in T/ET are linked to the different correlation lengths, as a result of the highly non‐linear relationship between potential T and % shrub cover, which indirectly take into account subsurface lateral flows in the root zone. Copyright © 2014 John Wiley & Sons, Ltd.
Role of the Isolable Hydride Intermediate in the Hydrosilylation of Carbonyl Compounds Catalyzed by the High‐Valent Mono‐Oxido–Rhenium(V) Complex
Authors: Huang Liangfang , Zhang Yu , Wei Haiyan 
Published: October 2014

AbstractThe hydrosilylation of carbonyl compounds catalyzed by high‐valent mono‐oxido–rhenium(V) complex [Re(O)Cl3(PPh3)2] (1) and its hydride [Re(O)(H)Cl2(PPh3)2] (1H) was theoretically investigated using density functional theory. Our calculations indicated that the most energetically favorable process for 1‐catalyzed hydrosilylation was the “ionic mechanistic pathway”. The catalytic cycle is initiated by carbonyl substrate nucleophilic attacks on the η1‐silane rhenium adduct, which results in the heterolytic cleavage of the Si–H bond and generation of a siloxy carbenium ion paired with an anionic rhenium hydride, [ReOCl3(H)(PPh3)]–[Me3SiOCHPh]+. The ionic mechanistic pathway is more favorable than the σ‐bond metathesis pathway that involves the generation of rhenium hydride (23.8 versus 31.5 kcal mol–1). Therefore, our results indicated that an undetected η1‐silane rhenium adduct was the real intermediate rather than the isolable hydride intermediate 1H in the hydrosilylation catalyzed by 1.
Synthesis, Structures, and Reactivity of Copper(I) Complexes Supported by a Rigid Dinucleating Ligand
Authors: Bheemaraju Amarnath , Beattie Jeffrey W. , Danylyuk Yury , Rochford Jonathan , Groysman Stanislav 
Published: October 2014

AbstractHerein, we report the diverse CuI chemistry of a dinucleating ligand L that features two iminopyridine chelates bridged by a 1,8‐diaminoxanthene linker {L = (1E,1′E)‐N,N′‐(2,7‐di‐tert‐butyl‐9,9‐dimethyl‐9H‐xanthene‐4,5‐diyl)bis[1‐(pyridin‐2‐yl)methanimine]}. The ligand L leads to the formation of discrete bimetallic species, or metallopolymers, as a result of syn‐parallel or anti‐parallel mutual disposition of the chelating units. The reaction of L with [Cu(NCMe)4]+ forms the discrete bimetallic complexes [Cu2(L)(NCMe)2]2+ (1) or [Cu2(L)2]2+ (2), depending on the solvent and the ligand‐to‐metal ratio. In contrast, the reaction of L with CuX (X = Cl, Br) forms the metallopolymers [Cu2(L)(Br)2]n (3) and {[Cu3(L)2Cl2][CuCl2]}n (4). The compounds were characterized by X‐ray crystallography, NMR spectroscopy, mass spectrometry, electrochemistry, and DFT calculations. The reaction of compound 1 with O2 in CH2Cl2 was found to lead to a mixture of CuII products of which tetrametallic [Cu4(L)4(OH)3(Cl)]4+ and [Cu4(L)2(OH)4]4+ were identified by X‐ray crystallography.
Synthetic Strategies for Variably Substituted Ruthenium–Imidazophenanthrolinium Complexes
Authors: Petermann Lydia , Staehle Robert , Pilz T. David , Sorsche Dieter , Görls Helmar , Rau Sven 
Published: October 2014

AbstractThe synthesis of several symmetric and asymmetric substituted imidazophenanthrolinium ligands and their corresponding ruthenium polypyridyl complexes was achieved by applying a newly designed synthetic concept. By testing different moieties, the advantages and limits of the synthetic approach could be defined. The substitution pattern on the imidazolium moiety has no significant influence on the structural aspects of the imidazophenanthrolinium backbone or on the photophysical properties of the ruthenium compounds. Given that imidazolium salts act as precursors for N‐heterocyclic carbenes, the reported results provide the basis for the design of highly efficient oligonuclear photocatalysts.
Switching the Macrocycle Conformation from Nonplanar to Planar in Cobalt(II) and Copper(II) β‐Tetra‐2′‐thienyl‐meso‐tetraphenylporphyrin Cocrystallates with C60
Authors: Bhyrappa Puttaiah , Sarangi Ujwal K. , Varghese Babu 
Published: October 2014

AbstractCrystal structures of cobalt(II) and copper(II) complexes of 2,3,12,13‐tetra‐2′‐thienyl‐5,10,15,20‐tetraphenylporphyrin/C60 cocrystallates were determined by single‐crystal XRD analysis. The crystal structures of the two cocrystallates, MTPP(2′‐thienyl)4·C60·(toluene)2 (M = CoII and CuII; TPP = tetraphenylporphyrin), compounds 1 and 2, respectively, are isomorphous and reveal a one‐dimensional (1D) supramolecular structure. In these cocrystallates, the macrocycle is almost planar within ±0.08 Å, as evidenced by comparing the value of ΔCb (the average deviation of the β‐pyrrole carbon from the porphyrin ring mean plane) with those for the nonplanar parent structures, CoTPP(2′‐thienyl)4 [±0.710(5) Å] and CuTPP(2′‐thienyl)4 [±0.546(2) Å]. This difference has been ascribed to intermolecular interactions and/or crystal packing forces.
Chiral Squaramide‐Catalyzed Sulfa‐Michael/Aldol Cascade for the Asymmetric Synthesis of Spirocyclic Tetrahydrothiophene Chromanone Derivatives
Authors: Zhao Bo‐Liang , Liu Lei , Du Da‐Ming 
Published: October 2014

AbstractA bifunctional squaramide‐catalyzed sulfa‐Michael/aldol cascade reaction between benzylidenechroman‐4‐ones and 1,4‐dithiane‐2,5‐diol with a low catalyst loading has been developed. This reaction constitutes a facile asymmetric synthesis of chiral spirocyclic tetrahydrothiophene chromanone derivatives with three contiguous stereocenters in high to excellent yields (up to 99 %) and with high enantioselectivities (up to 92 % ee). Additionally, a remarkable temperature effect on reaction efficiency was observed and gram‐scale syntheses were found to proceed smoothly with the same efficiency as smaller scale reactions.
Synthesis of Galactoclusters by Metal‐Free Thiol “Click Chemistry” and Their Binding Affinities for Pseudomonas aeruginosa Lectin LecA
Authors: Ligeour Caroline , Dupin Lucie , Marra Alberto , Vergoten Gérard , Meyer Albert , Dondoni Alessandro , Souteyrand Eliane , Vasseur Jean‐Jacques , Chevolot Yann , Morvan François 
Published: October 2014

AbstractMannose‐centered galactoclusters specific for lectin I of Pseudomonas aeruginosa (LecA) were synthesised by a combination of phosphoramidite chemistry and metal‐free thiol click chemistry (i.e., thiol addition to acrylamide or nucleophilic displacement of bromine in a bromoacetamide group by a thiol function). These thiol click reactions were performed with microwave assistance in the presence of Et3N and with use of a reducing agent to avoid disulfide formation. Nine tetravalent galactoclusters containing different linkers (aliphatic, oligoethyleneglycol or aromatic) were synthesised with a DNA tag. Their binding to LecA was monitored in a DNA‐based glycoarray and compared with that of a galactocluster synthesised by copper‐catalyzed azide–alkyne cycloaddition. The results indicated stronger binding of all galactoclusters relative to the monovalent galactoside but slightly weaker binding than that shown by the galactocluster incorporating a triazole ring, due to a favourable interaction of the latter with proline 51 of LecA.