Search results for "Proton"
showing 10 items of 5886 documents
Solution behaviour and relative stability of the complexes [MCl2(RNCHCHNR)] and [MCl2(py-2-CHNR)] (M=Pd, Pt;R=C6H4OMe-p)
1988
Abstract Even though the α-diimino complexes [MCl 2 (RNCHCHNR)] and [MCl 2 (py-2-CHNR)] (M=Pd, Pt;R=C 6 H 4 OMe- p ) are poorly soluble in chlorinated solvents, such as chloroform and 1,2-dichloroethane, or in acetonitrile, the electronic and 1 H NMR spectra indicate that these compounds are generally present as undissociate monomers with σ, σ′- N,N′ chelate N-ligands in dilute solutions. Only for [PdCl 2 (RNCHCHNR)], some dissociation of the α-diimine occurs in acetonitrile. In dimethylsulfoxide, where the solubility is much higher, no dissociation is observed for the pyridine-2-carbaldimine complexes [MCl 2 (py-2-CHNR)], whereas the 1,2-bis(imino) ethane derivatives [MCl 2 (RNCH…
Preparation and protonation of 2-pyrimidyl- and 2-pyrazylpalladium(II) complexes
1985
Abstract The oxidative addition of 2-chloropyrimidine or 2-chloropyrazine to [Pd(PPh 3 ) 4 ] yields a mixture of trans -[PdCl(C 4 H 3 N 2 - C 2 )(PPh 3 ) 2 ] (I) and [PdCl(μ-C 4 H 3 N 2 - C 2 , N 1 )(PPh 3 (II) (C 4 H 3 N 2 = 2-pyrimidyl or 2-pyrazyl group). The mononuclear complexes I are quantitatively converted into the binuclear species II upon treatment with H 2 O 2 . The reaction of II with HCl gives the N -monoprotonated derivatives cis -[PdCl 2 (C 4 H 4 N 2 - C 2 )(PPh 3 )] (III), from which the cationic complexes trans -[PdCl(C 4 H 4 N 2 - C 2 )(L) (L = PPh 3 , IV; PMe 2 Ph, V; PEt 3 , VI) can be prepared by ligand substitution reactions. Reversible proton dissociation occurs in so…
Chalcogenide-capped triiron clusters [Fe3(CO)9(μ3-E)2], [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) as proton-reduction…
2019
Chalcogenide-capped triiron clusters [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) have been examined as proton-reduction catalysts. Protonation studies show that [Fe3(CO)9(μ3-E)2] are unaffected by strong acids. Mono-capped [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] react with HBF4.Et2O but changes in IR spectra are attributed to BF3 binding to the face-capping carbonyl, while bicapped [Fe3(CO)7(μ3-E)2(μ-dppm)] are protonated but in a process that is not catalytically important. DFT calculations are presented to support these protonation studies. Cyclic voltammetry shows that [Fe3(CO)9(μ3-Se)2] exhibits two reduction waves, and upon addition of strong acids, proton-reducti…
Light-driven proton transport of bacteriorhodopsin incorporated into long-term stable liposomes of a polymerizable sulfolipid
1983
Abstract The chromoprotein bacteriorhodopsin from Halobacterium halobium has been incorporated into liposomes made of a fully synthetic, polymerizable lipid. Bacteriorhodopsin is found to be active in these polymer liposomes. The advantage in the use of such polymer systems concerning long-term stability in comparison with liposomes made of natural lipid is demonstrated.
1H NMR and UV-vis spectroscopic characterization of sulfonamide complexes of nickek(II)-carbonic anhydrase. Resonance assignments based on NOE effects
1992
The binding of acetazolamide, p-fluorobenzensulfonamide, p-toluenesulfonamide, and sulfanilamide to nickel(II)-substituted carbonic anhydrase II has been studied by 1H NMR and electronic absorption spectroscopies. These inhibitors bind to the metal ion forming 1:1 complexes and their affinity constants were determined. The 1H NMR spectra of the formed complexes show a number of isotropically shifted signals corresponding to the histidine ligands. The complexes with benzene-sulfonamides gave rise to very similar 1H NMR spectra. The NMR data suggest that these aromatic sulfonamides bind to the metal ion altering its coordination sphere. In addition, from the temperature dependence of 1H NMR s…
Inhibitoren der Korrosion (9) Nachweis der Sekundärinhibitoren bei einigen Sulfoxiden, Triphenylarsinoxid und einigen Sulfoniumsalzen
1971
Die Schutzwerte von Dibenzylsulf-oxyd und strukturell verwandten Ver-bindungen sowie von Triphenylarsin-oxyd werden bestimmt. Sulfoxyde und Arsinoxyde werden (a) nach Protonierung in die kathodischen Bereiche gefuhrt und (b) nach Elektronenaufnahme in die ko-ordinationsfahigen Sekundarinhibitoren (Thioather und tert. Arsine) umgewan-delt. Die Sekundarinhibitoren ziehen entweder auf das Metall auf und unter-drucken dann die Auflosung des Eisens oder werden nicht am Metall fixiert (z. B. Diphenylsulfid) und entfalten dann keinen Schutz. Im Falle des Dibenzyl-sulfoxyds konnen ca. 90% des einge-setzten Dibenzylsulfoxyds als Dibenzyl-sulfid vom Eisen abgelost werden; 16% an unverandertem Dibenzy…
Photoredox-catalyzed synthesis of N-unsubstituted enaminosulfones from vinyl azides and sulfinates
2021
Abstract A metal-free visible light photoredox-catalyzed synthesis of N-unsubstituted enaminosulfones from vinyl azides and sodium sulfinates in moderate to high yields is described. The reaction proceeds in ethanol and uses eosin Y as a readily available photocatalyst in combination with nitrobenzene as an electron shuttle. Taking into account the number of steps involved (generation of the sulfonyl radical, its addition to the double bond, elimination of molecular nitrogen with formation of an iminyl radical, followed by its reduction and protonation) as well as the number of redox-active reaction partners involved, the selectivity of the process is quite impressive.
Neutrino emission due to Cooper pairing of protons in cooling neutron stars: Collective effects
2000
The process of neutrino-pair radiation due to formation and breaking of Cooper pairs of protons in superconducting cores of neutron stars is considered with taking into account of the electromagnetic coupling of protons to ambient electrons. It is shown that plasma polarization strongly modifies the effective vector weak current of protons. Collective response of ambient electrons to the proton quantum transition contributes coherently to the complete interaction with the neutrino field and enhances the rate of neutrino-pair production by two orders of magnitude.
Highly sensitive superconducting circuits at ∼700 kHz with tunable quality factors for image-current detection of single trapped antiprotons
2016
We developed highly-sensitive image-current detection systems based on superconducting toroidal coils and ultra-low noise amplifiers for non-destructive measurements of the axial frequencies (550$\sim$800$\,$kHz) of single antiprotons stored in a cryogenic multi-Penning-trap system. The unloaded superconducting tuned circuits show quality factors of up to 500$\,$000, which corresponds to a factor of 10 improvement compared to our previously used solenoidal designs. Connected to ultra-low noise amplifiers and the trap system, signal-to-noise-ratios of 30$\,$dB at quality factors of > 20$\,$000 are achieved. In addition, we have developed a superconducting switch which allows continuous tu…
How deprotonation changes molecular self-assembly – an AFM study in liquid environment
2013
We study the influence of Alizarin Red S deprotonation on molecular self-assembly at the solid-liquid interface of the natural cleavage plane of calcite immersed in aqueous solution. To elucidate the adsorption details, we perform pH dependent high-resolution atomic force microscopy measurements. When Alizarin Red S is deposited onto calcite(10.4) in a liquid environment at an acidic pH of 5, weakly bound, ordered islands with a (3 x 3) superstructure are observed. A sharp structural transition is revealed when increasing the pH above 8. Above this pH, stable needle-like structures oriented along the [01.0] direction form on the surface. Comparing these results with potentiometric titration…