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861.
An ‘old' Rhodiumsulfide with surprising Structure – Synthesis, Crystal Structure, and Electronic Properties of Rh3S4 The reaction of rhodium with rhodium(III)‐chloride and sulfur at 1320 K in a sealed evacuated quartz glass ampoule yields silvery lustrous, air stable crystals of the rhodiumsulfide Rh3S4. Although a sulfide of this composition was described in 1935 a closer characterization has not been undertaken. Rh3S4 crystallizes in a new structure type in the monoclinic space group C2/m with a = 1029(2) pm, b = 1067(1) pm, c = 621.2(8) pm, β = 107.70(1)°. Besides strands of edge‐sharing RhS6 octahedra which are connected by S2 pairs (S–S = 220 pm), the crystal structure of Rh3S4 contains Rh6 cluster rings in chair conformation with Rh–Rh single bond lengths of 270 pm. Both fragments are linked by common sulfur atoms. Extended Hückel calculations indicate bonding overlap for both S–S‐ and Rh–Rh‐interactions. Rh3S4 has a composition between the neighboring phases Rh2S3 and Rh17S15 and the structure combines typical fragments of both: RhS6‐octahedra from Rh2S3 and domains of metal‐metal bonds as found in Rh17S15. Rh3S4 is a metallic conductor, down to 4.5 K the substance shows a weak, temperature independent paramagnetism. 相似文献
862.
Guangye Han Petko Chernev Stenbjrn Styring Johannes Messinger Fikret Mamedov 《Chemical science》2022,13(29):8667
Photosynthesis stores solar light as chemical energy and efficiency of this process is highly important. The electrons required for CO2 reduction are extracted from water in a reaction driven by light-induced charge separations in the Photosystem II reaction center and catalyzed by the CaMn4O5-cluster. This cyclic process involves five redox intermediates known as the S0–S4 states. In this study, we quantify the flash-induced turnover efficiency of each S state by electron paramagnetic resonance spectroscopy. Measurements were performed in photosystem II membrane preparations from spinach in the presence of an exogenous electron acceptor at selected temperatures between −10 °C and +20 °C and at flash frequencies of 1.25, 5 and 10 Hz. The results show that at optimal conditions the turnover efficiencies are limited by reactions occurring in the water oxidizing complex, allowing the extraction of their S state dependence and correlating low efficiencies to structural changes and chemical events during the reaction cycle. At temperatures 10 °C and below, the highest efficiency (i.e. lowest miss parameter) was found for the S1 → S2 transition, while the S2 → S3 transition was least efficient (highest miss parameter) over the whole temperature range. These electron paramagnetic resonance results were confirmed by measurements of flash-induced oxygen release patterns in thylakoid membranes and are explained on the basis of S state dependent structural changes at the CaMn4O5-cluster that were determined recently by femtosecond X-ray crystallography. Thereby, possible “molecular errors” connected to the e− transfer, H+ transfer, H2O binding and O2 release are identified.Temperature dependence of the transition inefficiencies (misses) for the water oxidation process in photosystem II were studied by EPR spectroscopy and are explained on the basis of S state dependent structural changes at the CaMn4O5-cluster. 相似文献
863.
Kilian Roßmann Kerem C. Akkaya Pascal Poc Corentin Charbonnier Jenny Eichhorst Hannes Gonschior Abha Valavalkar Nicolas Wendler Thorben Cordes Benjamin Dietzek-Ivani Ben Jones Martin Lehmann Johannes Broichhagen 《Chemical science》2022,13(29):8605
Rhodamine fluorophores are setting benchmarks in fluorescence microscopy. Herein, we report the deuterium (d12) congeners of tetramethyl(silicon)rhodamine, obtained by isotopic labelling of the four methyl groups, show improved photophysical parameters (i.e. brightness, lifetimes) and reduced chemical bleaching. We explore this finding for SNAP- and Halo-tag labelling in live cells, and highlight enhanced properties in several applications, such as fluorescence activated cell sorting, fluorescence lifetime microscopy, stimulated emission depletion nanoscopy and single-molecule Förster-resonance energy transfer. We finally extend this idea to other dye families and envision deuteration as a generalizable concept to improve existing and to develop new chemical biology probes.Deuteration enhances photophysical and chemical properties of fluorescent rhodamine dyes for higher brightness in sensitive microscopy. 相似文献
864.
865.
Jessica C. Bieniek Michele Grünewald Johannes Winter Dieter Schollmeyer Siegfried R. Waldvogel 《Chemical science》2022,13(27):8180
The use of electricity as a traceless oxidant enables a sustainable and novel approach to N,N′-disubstituted indazolin-3-ones by an intramolecular anodic dehydrogenative N–N coupling reaction. This method is characterized by mild reaction conditions, an easy experimental setup, excellent scalability, and a high atom economy. It was used to synthesize various indazolin-3-one derivatives in yields up to 78%, applying inexpensive and sustainable electrode materials and a low supporting electrolyte concentration. Mechanistic studies, based on cyclic voltammetry experiments, revealed a biradical pathway. Furthermore, the access to single 2-aryl substituted indazolin-3-ones by cleavage of the protecting group could be demonstrated.A novel sustainable electrochemical synthetic route to N,N′-disubstituted indazolin-3-ones by direct anodic oxidation with mild reaction conditions, a simple galvanostatic setup, broad scope and excellent scalability is established. 相似文献
866.
867.
868.
Syntheses and Structures of Magnesium Complexes with α, ω‐Dicarboxylato Ligands; Dicarboxylate = Succinate, Glutarate, and Suberate Crystals of (Tetraaqua)(succinato)magnesium ( 1 ), (Tetraaqua)(glutarato)magnesium ( 2 ) und (Triaqua)(suberato)magnesium ( 3 ) were obtained by layering an aqueous solution of the respective sodium salt with a solution of MgCl2 in isopropanol. In 1 a chain structure is realized. Mg(H2O)4 units are bridged in trans orientation by α, ω‐bonded succinate groups. 2 contains also chains. Glutarato groups are bonded in a cis fashion to Mg(H2O)4 units. They form bridges by using their two α O atoms. 3 represents a layer structure. The basic structural motives are α, α, ω‐bonded suberate, and fac‐Mg(H2O)3 units. All three structures contain efficient H bridging systems. The connection between the symmetry of the polymeric groups (chains or layer) and the symmetry of the underlying space groups is discussed. 1 : Space group P21/c, Z = 4, lattice constants at 20 °C: a = 7.441(2), b = 14.827(2), c = 7.771(2) Å; β = 99.77(3)°, R1 = 0.052. 2 : Space group C2/c, Z = 8, lattice constants at 20 °C: a = 12.867(2), b = 7.109(1), c = 21.683(3) Å; β = 107.33(2)°; R1 = 0.032. 3 : Space group P21/a, Z = 4, lattice constants at 20 °C: a = 9.174(2), b = 8.071(2), c = 15.960(3) Å; β = 104.29(2)°; R1 = 0.052. 相似文献
869.
Zarei M Bindila L Souady J Dreisewerd K Berkenkamp S Müthing J Peter-Katalinić J 《Journal of mass spectrometry : JMS》2008,43(6):716-725
Matrix-assisted laser desorption/ionization (MALDI) process of sialoglycoconjugates is generally accompanied by different levels of cleavage of sialic acid residues and/or by dehydration, and decarboxylation reactions. Quantitative densitometry of the mouse brain ganglioside (MBG) components separated by high-performance thin layer chromatography (HPTLC) and evidenced by orcinol staining was a basis to verify the ganglioside composition pattern with respect to the relative abundances of individual components in the mixture. A systematic mass spectrometry (MS) sialylation analysis has been carried out to evaluate the feasibility of an axial time-of-flight (a-TOF) MS, equipped with a vacuum MALDI source and an orthogonal-TOF (o-TOF) instrument with an ion source operated at about 1 mbar of N(2). Besides, the esterification by one methyl group of the carboxyl group in sialic acid to increase the stability of the ganglioside species for MALDI MS analysis has been tested and the yield of intact ganglioside species and of the neutral loss of water and carbon dioxide estimated. For the sialylation analysis of native ganglioside mixtures the MALDI o-TOF analysis with 6-azo-2-thiothymine/diammonium citrate (ATT/DAC) as a matrix appears as an optimal approach for ganglioside profiling. 相似文献
870.
Baldé CP Hereijgers BP Bitter JH de Jong KP 《Angewandte Chemie (International ed. in English)》2006,45(21):3501-3503