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101.
M.Sc. Jan Schulz Dr. Menyhárt B. Sárosi Prof. Dr. Evamarie Hey-Hawkins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(34):e202200531
The primary phosphines MesPH2 and tBuPH2 react with 9-iodo-m-carborane yielding B9-connected secondary carboranylphosphines 1,7-H2C2B10H9-9-PHR (R=2,4,6-Me3C6H2 (Mes; 1 a ), tBu ( 1 b )). Addition of tris(pentafluorophenyl)borane (BCF) to 1 a , b resulted in the zwitterionic compounds 1,7-H2C2B10H9-9-PHR(p-C6F4)BF(C6F5)2 ( 2 a , b ) through nucleophilic para substitution of a C6F5 ring followed by fluoride transfer to boron. Further reaction with Me2SiHCl prompted a H−F exchange yielding the zwitterionic compounds 1,7-H2C2B10H9-9-PHR(p-C6F4)BH(C6F5)2 ( 3 a , b ). The reaction of 2 a , b with one equivalent of R'MgBr (R’=Me, Ph) gave the extremely water-sensitive frustrated Lewis pairs 1,7-H2C2B10H9-9-PR(p-C6F4)B(C6F5)2 ( 4 a , b ). Hydrolysis of the B−C6F4 bond in 4 a , b gave the first tertiary B-carboranyl phosphines with three distinct substituents, 1,7-H2C2B10H9-9-PR(p-C6F4H) ( 5 a , b ). Deprotonation of the zwitterionic compounds 2 a , b and 3 a , b formed anionic phosphines [1,7-H2C2B10H9-9-PR(p-C6F4)BX(C6F5)2]−[DMSOH]+ (R=Mes, X=F ( 6 a ), R=tBu, X=F ( 6 b ); R=Mes, X=H ( 7 a ), R=tBu, X=H ( 7 b )). Reaction of 2 a , b with an excess of Grignard reagents resulted in the addition of R’ at the boron atom yielding the anions [1,7-H2C2B10H9-9-PR(p-C6F4)BR’(C6F5)2]− (R=Mes, R’=Me ( 8 a ), R=tBu, R’=Me ( 8 b ); R=Mes, R’=Ph ( 9 a ), R=tBu, R’=Ph ( 9 b )) with [MgBr(Et2O)n]+ as counterion. The ability of the zwitterionic compounds 3 a , b to hydrogenate imines as well as the Brønsted acidity of 3 a were investigated. 相似文献
102.
Jan Rosenboom Dr. Lukas Chojetzki Dr. Tim Suhrbier Dr. Jabor Rabeah Dr. Alexander Villinger Dr. Ronald Wustrack Dr. Jonas Bresien Prof. Dr. Axel Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(36):e202200624
The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ-NTer)2P⋅] ( 1 ) (Ter=2,6-bis-(2,4,6-trimethylphenyl)-phenyl) is reported, yielding trans-addition products of the type [Br−P(μ-NTer)2P−R] ( 2 ), so-called 1,3-substituted cyclo-1,3-diphospha-2,4-diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo-1,3-diphospha-2,4-diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in-situ detection of the phosphorus-centered monoradical [⋅P(μ-NTer)2P-R].< To provide further evidence for the radical mechanism, [⋅P(μ-NTer)2P-Et] ( 3Et ⋅) was synthesized directly by reduction of the bromoethane addition product [Br-P(μ-NTer)2P-Et] ( 2 a ) with magnesium, resulting in the formation of the persistent phosphorus-centered monoradical [⋅P(μ-NTer)2P-Et], which could be isolated and fully characterized, including single-crystal X-ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ-NTer)2P-Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ-NTer)2P⋅] ( 1 ) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ-NTer)2P⋅] with EtBr. In the field of hetero-cyclobutane-1,3-diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P-centered biradicals and P-centered monoradicals in terms of radical reactivity. 相似文献
103.
Matthias Ermer Julian Mehler Björn Rosenberger Dr. Marcus Fischer Dr. Peter S. Schulz Prof. Martin Hartmann 《ChemistryOpen》2021,10(2):233-242
Using ionic liquids (ILs) as linker precursors, the well-known metal-organic framework (MOF) UiO-66 (Universitetet i Oslo) and the recently reported MOF hcp UiO-66 (hexagonal closed packed) have been successfully synthesized and characterized. The advantage of the applied novel synthesis approach is an economically and environmentally benign work-up procedure, due to the better solubility of the IL. Additionally, the reactivity of the terephthalate anions is increased compared to terephthalic acid, resulting in faster MOF formation with an increased amount of defects in the MOF structure. In order to explore to the influence of defects on the catalytic performance, the cyclisation of citronellal to isopulegol was employed as test reaction. The activity of hcp UiO-66 and fcc UiO-66 (face centered cubic) is improved compared to other MOF or zeolite based catalysts, while the selectivity is similar. 相似文献
104.
P. Müller‐Buschbaum J. Perlich M. M. Abul Kashem L. Schulz S. V. Roth Y. J. Cheng J. S. Gutmann 《固体物理学:研究快报》2007,1(3):119-121
Nanostructures formed in a titanium dioxide (TiO2)–poly(styrene)‐block‐poly(ethyleneoxide) nanocomposite film on top of fluor‐doped tin oxide (FTO) layers are investigated. The combinatorial approach is based on probing a wedge‐shaped FTO‐gradient with grazing incidence small angle X‐ray scattering (GISAXS) in combination with a moderate micro‐focus X‐ray beam. The characteristic lateral length is given by adjacent nanowire‐shaped TiO2 regions. It decreases from 200 nm on the thick FTO layer to 90 nm on the bare glass surface.
105.
Prof. Dr. Tunga Salthammer Friederike Monegel Nicole Schulz Dr. Erik Uhde Prof. Dr. Stefan Grimme Jakob Seibert Prof. Dr. Uwe Hohm Dr. Wolf-Ulrich Palm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):1046-1056
The chemical background of olfactory perception has been subject of intensive research, but no available model can fully explain the sense of smell. There are also inconsistent results on the role of the isotopology of molecules. In experiments with human subjects it was found that the isotope effect is weak with acetone and D6-acetone. In contrast, clear differences were observed in the perception of octanoic acid and D15-octanoic acid. Furthermore, a trained sniffer dog was initially able to distinguish between these isotopologues of octanoic acid. In chromatographic measurements, the respective deuterated molecule showed weaker interaction with a non-polar liquid phase. Quantum chemical calculations give evidence that deuterated octanoic acid binds more strongly to a model receptor than non-deuterated. In contrast, the binding of the non-deuterated molecule is stronger with acetone. The isotope effect is calculated in the framework of statistical mechanics. It results from a complicated interplay between various thermostatistical contributions to the non-covalent free binding energies and it turns out to be very molecule-specific. The vibrational terms including non-classical zero-point energies play about the same role as rotational/translational contributions and are larger than bond length effects for the differential isotope perception of odor for which general rules cannot be derived. 相似文献
106.
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109.
Aysu Yarman Christopher Schulz Cristoph Sygmund Roland Ludwig Lo Gorton Ulla Wollenberger Frieder W. Scheller 《Electroanalysis》2014,26(9):2043-2048
For the first time the direct electron transfer of an enzyme ‐ cellobiose dehydrogenase, CDH ‐ has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1 : 1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag|AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference‐free and oxygen‐independent measurement of ATP in the lower µmolar concentration range with a lower limit of detection of 63.3 nM (S/N=3). 相似文献
110.
Spectroscopic and Computational Study of a Nonheme Iron Nitrosyl Center in a Biosynthetic Model of Nitric Oxide Reductase 下载免费PDF全文
Dr. Saumen Chakraborty Julian Reed Matthew Ross Dr. Mark J. Nilges Igor D. Petrik Dr. Soumya Ghosh Prof. Dr. Sharon Hammes‐Schiffer Prof. Dr. J. Timothy Sage Prof. Dr. Yong Zhang Prof. Dr. Charles E. Schulz Prof. Dr. Yi Lu 《Angewandte Chemie (International ed. in English)》2014,53(9):2417-2421
A major barrier to understanding the mechanism of nitric oxide reductases (NORs) is the lack of a selective probe of NO binding to the nonheme FeB center. By replacing the heme in a biosynthetic model of NORs, which structurally and functionally mimics NORs, with isostructural ZnPP, the electronic structure and functional properties of the FeB nitrosyl complex was probed. This approach allowed observation of the first S=3/2 nonheme {FeNO}7 complex in a protein‐based model system of NOR. Detailed spectroscopic and computational studies show that the electronic state of the {FeNO}7 complex is best described as a high spin ferrous iron (S=2) antiferromagnetically coupled to an NO radical (S= 1/2) [Fe2+‐NO.]. The radical nature of the FeB‐bound NO would facilitate N? N bond formation by radical coupling with the heme‐bound NO. This finding, therefore, supports the proposed trans mechanism of NO reduction by NORs. 相似文献