Abstract A new Zintl cluster [Ge9PdPPh3]3− has been isolated as (2,2,2-crypt)K+ salt through the reaction of K4Ge9 and Pd[PPh3]4 in ethylenediamine solutions and characterized via single-crystal X-ray crystallography. The as-prepared bimetallic [Ge9PdPPh3]3− cluster could successfully trap a nickel atom to form a trimetallic cluster [Ni@(Ge9PdPPh3)]2−. The coordination of Ge94− by PdPPh3 induces a one-electron oxidation and encapsulation of the Ni atom into the Ge93− cage leads to a further one-electron oxidation and a geometry transformation from C4v (nido) to C3v (closo).
Graphical Abstract
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
It is frequently said that DESI-MS follows a similar ionization mechanism as ESI because of similarities usually observed in their respective mass spectra. However, practical use of DESI-MS for protein analysis is limited to proteins with lower molecular weights (<?25 kDa) due to a mass-dependent loss in signal intensity. Here we investigated commonly used volatile acids and their ammonium salt buffers for DESI-MS analysis of protein. We noticed that, surprisingly, some additives influence the analysis differently in DESI compared to ESI. Improved signal intensities with both DESI and ESI were obtained when acetic and formic acid were added into aqueous methanol spray solvents with both DESI and ESI. On the other hand, while with ESI the addition of ammonium salts into spray solutions strongly reduced both signal and S/N, with DESI signal intensities and S/N were improved dramatically. Ammonium bicarbonate when used with DESI reduced the total amount of adduction and delivered excellent signal-to-noise ratios with high intensity; however, it also denatures protein. When native state protein mass spectra are preferred, ammonium acetate would also deliver reasonable adduct removal and improved S/N. The amount of total adduction of individual adducting species and of all species could not be correlated with differences in either solutions pH values or with proton affinities of the anions. An obvious difference between DESI and ESI mass spectrometry is the effects of protein solubility during droplet pickup (desorption), but differences in the sizes, velocities, and composition of ionizing droplets were also discussed as important factors.
Abstract The synthesis of 4H-thiochromene derivatives of apomorphines, a novel class of isoquinoline alkaloid-related compounds, has been achieved by
different O-dealkylation methods applied on previously published heteroring-fused aporphinoids. Detailed DFT study has been presented
regarding the mechanism of the L-selectride-mediated multiple O-dealkylation of a seven-ring aporphine analogue. Dopamine-binding tests confirmed the essential function of 11-hydroxy moiety
of the aporphine skeleton and revealed a remarkable D1 over D2 specificity for the derivative having the 4H-thiochromene ring system attached to positions 2 and 3 of the aporphine backbone.
Graphical Abstract
Amperometric detection is ideally suited for integration into micro- and nanofluidic systems as it directly yields an electrical
signal and does not necessitate optical components. However, the range of systems to which it can be applied is constrained
by the limited sensitivity and specificity of the method. These limitations can be partially alleviated through the use of
redox cycling, in which multiple electrodes are employed to repeatedly reduce and oxidize analyte molecules and thereby amplify
the detected signal. We have developed an interdigitated electrode device that is encased in a nanofluidic channel to provide
a hundred-fold amplification of the amperometric signal from paracetamol. Due to the nanochannel design, the sensor is resistant
to interference from molecules undergoing irreversible redox reactions. We demonstrate this selectivity by detecting paracetamol
in the presence of excess ascorbic acid.
Figure
Abstract DFT calculations of the complex ions {(μ4-TCNX)[Ru(NH3)5]4}8+, TCNX = tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), yield triplet state energy minimum structures with nonplanar bridging ligands. The calculated C–C
bond distances and twist angles confirm considerable metal-to-ligand electron transfer from the metal centers to the TCNE
and TCNQ bridges in the lowest triplet and singlet states. The resulting situation, involving a weak interaction between two
strongly coupled malonodinitrilato-bridged Ru2.5Ru2.5 entities (Class III), agrees with experimental results; the near-orthogonality found for the ground states of the molecular
ions explains the observed magnetic exchange coupling between two S = 1/2 sites, the 1,258 cm−1 absorption in the IR spectrum of the TCNE complex, and the reversible two-electron oxidation. The nitrile stretching frequency
shifts were reasonably reproduced by the calculations. A density-of-states representation for the TCNQ complex shows a rather
different electronic structure in comparison to that for the formally related {(μ4-TCNQ)[Re(CO)3(bpy)]4}4+, in particular a different frontier orbital situation. In contrast to the (TCNQ0)(ReI)4 situation, the tetraruthenium species with an approximate (TCNX2−)(Ru2.5)4 formulation represent unconventional mixed-valent tetranuclear compounds; in other words, weakly coupled pairs of strongly
coupled dinuclear moieties. EPR spectroscopy at the W band frequency (95 GHz) of the TCNE compound confirms that the reduction
of the complex leads to the oxidation of TCNE2− to yield a (TCNE•−)(RuII)4 species.
Graphical abstract
Desorption electrospray ionization (DESI), an established ambient ionization method in mass spectrometry (MS) for the analysis
of organic compounds, is applied here to trace detection of inorganic salts, including inorganic oxidants. In-situ surface
analysis of targeted compounds, including nitrogen-, halogen- and sulfur-salts, down to sub-nanogram levels, was performed
using DESI-MS. Successful experiments were carried out in both the negative and the positive ion modes; simple anions and
cations as well as small cluster ions were observed. Various surfaces are examined and surface porosity effects were briefly
explored. Absolute detection limits on porous polytetrafluoroethylene (PTFE) of 120 pg (surface concentration 0.07 ng mm−2) and 50 pg (surface concentration 0.03 ng mm−2), were achieved for sodium chlorate and sodium perchlorate, respectively. The compounds of interest were examined in the
presence of a hydrocarbon mixture to assess matrix effects: only a two- or three-fold decrease in the target ion intensity
was observed. Commercial fireworks were analyzed to determine perchlorate salts in complex mixtures. This work demonstrates
the potential applicability of ambient ionization mass spectrometry to forensic investigations involving improvised explosives.
相似文献
Abstract Mixed-ligand NiII complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined
by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky
ligands on the coordination distances and spectral properties are discussed.
Graphical Abstract
Abstract Six 10-nor-bilirubin analogs have been synthesized and investigated. Lacking the C(10) CH2 group, these linear tetrapyrroles have a bipyrrole core rather than a dipyrrylmethane core and thus a different shape. Whereas
the propionic acid groups of bilirubin are well engaged in intramolecular hydrogen bonding to the dipyrrinones, molecular
modeling studies of the 10-nor-rubins predict that propionic acid chains are too short to engage the CO2H hydrogen fully in intramolecular hydrogen bonding with the dipyrrinones. Butyric acid chains, however, can and do lead to
a stabilized conformation with a bipyrrole dihedral angle of approximately 115°. Spectroscopic studies verify the predictions
and vapor pressure osmometry indicates that the 10-nor-rubins with butyric acids are monomeric in CHCl3.
Graphical abstract
Hydrazone-based receptor containing electron-withdrawing chromogenic substituents 1,10-phenanthroline-2,9-di-carboxaldehydic-(2,4-dinitrophenyl)-hydrazone
(1) has been synthesized. The interaction with different anions via hydrogen bonding was demonstrated by UV-Vis absorption spectroscopy
to give a purple 1:1 complexes in DMSO, whose association constant decreases in line with the following order of the studied
anions (AcO− > F− > H2PO4− > OH− >>Cl−∼Br−∼I−). As a naked-eyes colorimetric sensor for anions, the study has a latent application importance.
相似文献
Free-flow electrophoresis (FFE) is a technique that performs an electrophoretic separation on a continuous stream of analyte
as it flows through a planar flow channel. The electric field is applied perpendicularly to the flow to deflect analytes laterally
according to their mobility as they flow through the separation channel. Miniaturization of FFE (μFFE) over the past 15 years
has allowed analytical and preparative separation of small volume samples. Advances in chip design have improved separations
by reducing interference from bubbles generated by electrolysis. Mechanisms of band broadening have been examined theoretically
and experimentally to improve resolution in μFFE. Separations using various modes such as zone electrophoresis, isoelectric
focusing, isotachophoresis, and field-step electrophoresis have been demonstrated.
Michael T. BowserEmail:
Michael T. Bowser
is currently an Associate Professor at the University of Minnesota where he has been a faculty member in the Department of
Chemistry since 2000. Michael was the 2005 recipient of the ACS Award for Young Investigators in Separation Science. His research
interests include microfluidic devices, high-speed neurotransmitter measurements and techniques for isolating high-affinity
aptamers.
相似文献
Abstract Photoinitiated cationic polymerizations of various epoxy monomers bearing a carbazole moiety, 9-[3-(allyloxy)-2-(oxiran-2-ylmethoxy)propyl]-9H-carbazole, 9-[3-methoxy-2-(oxiran-2-ylmethoxy)propyl]-9H-carbazole, 9-[2-(oxiran-2-ylmethoxy)ethyl]-9H-carbazole, as well as a composition of 3,6-dibromo-9-(oxiran-2-ylmethyl)-9H-carbazole with 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate were investigated in bulk using triphenyl carbenium
salts having anions such as BF4−, SnCl5−, and SbCl6−. Dark polymerizations of the carbazolyl monomers in the presence of the initiators are studied. These photoinduced polymerization
reactions give oligomers of degree of polymerization 4-22. The effect of the anion of the photoinitiator and polymerization
time on the polymerization reaction is discussed.
Graphical abstract
相似文献
This work demonstrates the capabilities of nanoscale secondary-ion mass spectrometry, using the Cameca NanoSIMS50 ion microprobe,
to detect and image the copper-ion distribution in microalgal cells exposed to nanomolar and micromolar copper concentrations.
In parallel to 63Cu− secondary-ion maps, images of 12C−, 12C14N−, and 31P− secondary ions were collected and analysed. A correlation of 63Cu− secondary-ion maps with those found for 12C14N− and 31P− demonstrated the possible association of Cu with cell components rich in proteins and phosphorus. The results highlighted
the potential of NanoSIMS for intracellular tracking of essential trace elements such as Cu in single cells of the microalga
Chlorella kesslerii.
Figure
12C14N-, 63Cu- secondary-ion distributions in algal cell 相似文献
Abstract Internal and external interfaces in solids exhibit completely different transport properties compared to the bulk. Transport
parallel to grain or phase boundaries is usually strongly enhanced. Transport perpendicular to an interface is usually blocked,
i.e., transport across an interface is often much slower. Due to the high density of interfaces in modern micro- and nanoscaled
devices, a severe influence on the total transport properties can be expected. In contrast to diffusion in metal grain boundaries,
transport phenomena in boundaries of ionic materials are still less understood. The specific transport properties along metal
grain boundaries are explained by structural factors like packing densities or dislocation densities in the interface region.
In most studies dealing with ionic materials, the interfacial transport properties are merely explained by the influence of
space charge regions. In this study the influence of the interface structure on the interfacial transport properties of ionic
materials is discussed in analogy to metallic materials. A qualitative model based on the density of misfit dislocations and
on interfacial strain is introduced for (untilted and untwisted) phase boundaries. For experimental verification, the interfacial
ionic conductivity of different multilayer systems consisting of stabilised ZrO2 and an insulating oxide is investigated as a funtion of structural mismatch. As predicted by the model, the interfacial conductivity
increases when the lattice mismatch is increased.
Graphical abstract
A new receptor, the bisTTF-calix[2]thiophene[2]pyrrole derivative 3, has been prepared from the Lewis acid-catalyzed condensation of 2,5-bis(1-hydroxymethylethyl)thiopheno-TTF and pyrrole.
This new system is found to form complexes with the electron-deficient guests, trinitrobenzene (TNB) and picric acid (PA),
which serve as models for nitroaromatic explosives. The binding phenomenon, which has been studied in organic solution using
proton nuclear magnetic resonance and absorption spectroscopies, results in an easy-to-visualize color change in chloroform
that is independent of the presence of chloride anion, a known interferant for an earlier tetrakisTTF-calix[4]pyrrole TNB
chemosensor. Support for the proposed binding mode comes from a preliminary solid state structure of the complex formed from
TNB, namely TNB⊂3. A color change is also observed when dichloromethane solutions of chemosensor 3 are added to solvent-free samples of TNB, PA, and 2,4,6-trinitrotoluene supported on silica gel.
Figure A new bis-tetrathiafulvalene calix[2]thiophene[2]pyrrole derivative has been prepared that gives rise to an easy-to-visualize
color change in the presence of the model nitroaromatic explosives trinitrobenzene and picric acid.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Abstract (+)-Lortalamine was synthesised using (S)-(−)-α-methylbenzylamine as a chiral auxiliary. The stereochemistry of an intermediate compound was established on the basis
of X-ray crystallography, allowing unambiguous assignment of the absolute configuration.
Graphical abstract
相似文献
Abstract The synthesis and acid-catalyzed rearrangement of novel thiazolomorphinandienes have been presented. An isomerization was
observed simultaneously with the backbone transformation. An extensive study was performed to determine the major effects
of the isomerization of 2′-alkyl- and aryl-substituted thiazoloapocodeines into 3′-alkyl- and arylisothiazoloapocodeines.
The obtained results provided another practical example of the reversible benzisothiazole–benzothiazole-type isomerization
emphasizing the determining role of the thermal effects in the occurrence of these isomerization products. The obtained experimental
results and the proposed mechanism were in agreement with the calculated DFT data.
Graphical abstract
The paper presents an analytical method developed for the nondestructive study of nineteenth-century Persian polychrome underglaze
painted tiles. As an example, 9 tiles from French and German museum collections were investigated. Before this work was undertaken
little was known about the materials used in pottery at that time, although the broad range of colors and shades, together
with their brilliant glazes, made these objects stand out when compared with Iranian ceramics of the preceding periods and
suggested the use of new pigments, colorants, and glaze compositions. These materials are thought to be related to provenance
and as such appropriate criteria for art-historical attribution. The analytical method is based on the combination of different
nondestructive spectroscopic techniques using microfocused beams such as proton-induced X-ray emission/proton-induced γ-ray
emission, X-ray fluorescence, 3D X-ray absorption near edge structure, and confocal Raman spectroscopy and also visible spectroscopy.
It was established to address the specific difficulties these objects and the technique of underglaze painting raise. The
exact definition of the colors observed on the tiles using the Natural Color System?? helped to attribute them to different colorants. It was possible to establish the presence of Cr- and U-based colorants as
new materials in nineteenth-century Persian tilemaking. The difference in glaze composition (Pb, Sn, Na, and K contents) as
well as the use of B and Sn were identified as a potential marker for different workshops.
Figure UV fluorescence and visible spectroscopy are two of the non-destructive analytical methods used to investigate the coloring
agents of underglaze painted tiles. Imaging of the uranium-containing areas was carried out by UV photography and identification
of the chemical species by visible spectroscopy.
Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to determine the bulk metal elemental composition
of 62 modern bronze sculptures cast in Paris in the first half of the twentieth century from the collections of The Art Institute
of Chicago and the Philadelphia Museum of Art. As a result, a comprehensive survey of the alloy composition of the sculptures
of many prominent European artists of the early twentieth century is presented here for the first time. The sculptures in
this study consist of predominantly copper with two main alloying elements (zinc and tin). By plotting the concentrations
of these two elements (zinc and tin) against each other for all the sculptures studied, three clusters of data become apparent:
(A) high-zinc brass; (B) low-zinc brass; (C) tin bronze. These clusters correlate to specific foundries, which used specific
casting methods (sand or lost wax) that were influenced by individual preferences and technical skills of the foundry masters.
For instance, the high-zinc brass alloys (with the highest levels of tin and zinc and the lowest melting temperature) correspond
to most of the Picasso sculptures, correlate with the Valsuani foundry, and are associated with the most recent sculptures
(post-WWII) and with the lost-wax casting method. By expanding the ICP-OES database of objects studied, these material correlations
may become useful for identifying, dating, or possibly even authenticating other bronzes that do not bear foundry marks.
Figure
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Liquid polymer membrane electrodes based on nickel and manganese phthalocyanines were examined for use as anion-selective
electrodes. The electrodes were prepared by incorporating the ionophores into plasticized poly(vinyl chloride) membranes,
which were directly coated onto the surfaces of graphite electrodes. The resulting electrodes demonstrate near-Nernstian responses
over a wide linear range of perchlorate anion (5 × 10−7 to 1 × 10−1 M). The electrodes have a fast response time, submicromolar detection limits (5 × 10−7 M perchlorate), and could be used over a wide pH range of 3.5–10. The influences of lipophilic cationic and anionic additives
on the response properties of the electrodes were investigated. The proposed sensors revealed high selectivity for perchlorate
over a number of common inorganic and organic anions. The highest selectivity was observed for the electrode based on manganese
phthalocyanine in the presence of the lipophilic anionic additive sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. Application
of the electrodes to determine perchlorate in tap water and human urine is also reported.
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