Reaktionen von Oxovanadium-Dipicolinatokomplexen mit Benzoylhydrazin. Die Kristallstrukturen von [VO(dipic)(NH2NHC(O)Ph) · NH2NHC(O)Ph · H2O, [C(NH2)3][VO(dipic)(NHNC(O)Ph)] · 2H2O und der „blauen“ Modifikation von [VO(dipic)(H2O)2] · 2H2O / Reactions of Oxovanadium(IV) and -(V) Dipicolinato Complexes with Benzoylhydrazine. Crystal Structures of [VO(dipic)(NH2NHC(O)Ph)] · NH2NHC(O)Ph · H2O · [C(NH2)3][VO(dipic)(NHNC(0)Ph)] · 2H 2O and the “Blue” Modification of [VO(dipic)(H2O) 2] · 2 H2O

1993 ◽  
Vol 48 (2) ◽  
pp. 125-132 ◽  
Author(s):  
Angelika Sundheim ◽  
Rainer Mattes
Keyword(s):  
Multiple Bond ◽  
Resonance Spectroscopy ◽  
Space Group ◽  
Bond Lengths ◽  
Spin Resonance ◽  
Pyridine Dicarboxylic Acid ◽  
In Trans ◽  
Carbonyl Bond ◽  
Axial Site ◽  
Bond Character

AbstractThe hydrazino complex [VO(dipic)(NH2NHC(O)Ph)] · NH2NHC(O)Ph · H2O (3) has been prepared by reaction of [VO(dipic)(H2O)] · 2H2O (1) with NH2NHC(O)Ph. (dipic = dianion of pyridine dicarboxylic acid). The hydrazido(2-) complex (guanid)[VO(dipic)(NHNC(O)Ph)] · 2H2O (4) was obtained by reaction of (guanid)[VO2(dipic)]·2H2O and NH2NHC(O)Ph. During the course of this reaction a terminally bonded oxygen atom is abstracted from the vanadium(V) center. 1, 3 and 4 have been characterized by X-ray single crystal diffraction, infrared, Raman and electron spin resonance spectroscopy.In 1 vanadium is six-coordinate, with the nitrogen atom of the dipic ligand in trans position to the oxo group. The two water molecules are also ligated in mutual trans positions. Vanadium is also six-coordinate in 3 and 4. In both, the dipic ligand is cis oriented with respect to the terminal oxo group. In 3 benzoylhydrazine, and in 4 the hydrazido(2 -) species NHNC(O)Ph act as N,O-chelate ligands, donating their NH2-, respectively NH-group to the remaining equatorial site and their CO-group to an axial site. The V - NH2(213.1(4) pm) and V - NH (190.5(2) pm) bond lengths differ considerably, indicating multiple bond character for the latter. In 3 the V -O(oxo) and V-O (carbonyl) bond lengths are 160.1(4) and 219.1(3) pm, and in 4 160.8(2) and 211.9(2) pm, respectively. Crystal data for 1: space group P 1̄, a = 656.2(2), b = 913.2(3), c - 1075.2(2) pm, α= 111.44(2), β = 100.16(2), γ = 94.81(3)°, Z = 2; 3: space group P1̄, a = 801.4(2), b = 1188.7(11), c = 1353.5(12) pm, α = 72.02(7), β = 88.31(7), γ = 70.60(7)°, Z = 2; 4: space group P 1̄, a = 1018.2(5), b = 1222.5(6), c = 1683.2(6) pm, α = 80.02, β = 89.95, γ = 78.73°, Z = 4.

Sr3Al2Ge4, Ca10Al6Ge9 und Ca20Al6Ge13. Neue Aluminium-Germanide / Sr3Al2Ge4, Ca10Al6Ge9 and Ca20Al6Ge13. New Aluminium Germanides

2007 ◽  
Vol 62 (8) ◽  
pp. 1071-1082 ◽  
Author(s):  
Marco Wendorff ◽  
Caroline Röhr
Keyword(s):  
Small Deviation ◽  
Multiple Bond ◽  
Ternary Systems ◽  
Monoclinic Space Group ◽  
Band Structure Calculation ◽  
Total Density ◽  
Space Group ◽  
The One ◽  
Total Density Of States ◽  
Bond Character

In the ternary systems Ca-Al-Ge and Sr-Al-Ge three germanides with new structure types have been synthesized from stoichiometric ratios of the elements. Their crystal structures were determined using single crystal X-ray data. In the structure of Sr3Al2Ge4 (monoclinic, space group C2/m, a = 1267.6(4), b = 416.2(2), c = 887.4(3) pm, β = 110.37(2)°, Z = 2, R1 = 0.0354) Al-Ge sheets with Al in tetrahedral (i. e. Al−) and Ge in threefold ψ-tetrahedral (i. e. Ge−) coordination against Ge are present. Thus, the compound can be classified as an electron precise Zintl phase. This finding is verified by the result of a band structure calculation (within the FP-LAPW approach), that shows a distinct minimum of the total density of states at the Fermi level. The structure of Ca10Al6Ge9 (trigonal, space group R3̅m, a = 1398.45(14), c = 2107.4(3) pm, Z = 6, R1 = 0.0613) contains complicated sheets of trigonal planar building units [AlGe3] and [AlGe4] tetrahedra. The compound Ca20[Al3Ge6]2[Ge] (hexagonal, space group P63/m, a = 1600.9(2), c = 458.48(7) pm, Z = 1, R1 = 0.0282) shows two planar trimers of [AlGe3] triangles of formula [Al3Ge6] besides isolated Ge atoms (i. e. Ge4−). The overall electron count of the latter compounds, that contain trigonal planar coordinated Al atoms and considerable multiple bond character of the Al-Ge bonds, shows a very small deviation from the Zintl concept, comparable to the one observed in other aluminium-germanides like SrAlGe.

Synthese und Kristallstruktur des Phosphaniminatokomplexes [MoCl4(NPPh3)(Pyridin)] · CH2Cl2/ Synthesis and Crystal Structure of the Phosphaneiminato Complex [MoCl4(NPPh3)(pyridine)] · CH2Cl2

1987 ◽  
Vol 42 (8) ◽  
pp. 947-950 ◽  
Author(s):  
Karin Völp ◽  
Frank Weller ◽  
Kurt Dehnicke
Keyword(s):  
Crystal Structure ◽  
Unit Cell ◽  
Pyridine Molecule ◽  
Trans Position ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
Bond Lengths ◽  
Cell Dimensions ◽  
In Trans ◽  
Moisture Sensitive

Abstract[MoCl4(NPPh3)(pyridine)] · CH2Cl2 is formed by the reaction of the cyclothiazeno complex [MoCl3(N3S2) · (pyridine)] with triphenylphosphane in CH2Cl2 solution. It forms red, moisture sensitive needles. [MoCl4(NPPh3)(C5H5N)] · CH2Cl2 crystallizes monoclinically in the space group P21/n with four formula units per unit cell (1934 independent observed reflexions. R = 0.057). The cell dimensions are a = 1165, b = 1473, c = 1696 pm; β = 107.82°. The Mo atom is coordinated by four chlorine atoms, by the N atom of the (NPPh3-) ligand, and in trans-position to it by the N atom of the pyridine molecule. The Mo= N = PPh3 group has a nearly linear MoNP axis (176.6°) with bond lengths of MoN = 172 pm and PN = 165 pm.

Fluoro-, Chloro- und Bromo-Wolfram(VI)-Alkinkomplexe. Die Kristallstrukturen von [K(18-Krone-6)][WF5(Ph – C≡C – H)] · CH3CN und [WCl4(Ph – C ≡ C – Se – n – C4H9)(CH3CN)] / Fluoro-, Chloro-, and Bromo-Tungsten(VI) Alkyne Complexes. The Crystal Structures of [K(18-Crown-6)][WF5(Ph — C ≡ C — H)] · CH3CN and [WCl4(Ph — C ≡ C — Se — n — C4H9)(CH3CN)]

1991 ◽  
Vol 46 (8) ◽  
pp. 999-1010 ◽  
Author(s):  
Petra Neumann ◽  
Kurt Dehnicke ◽  
Dieter Fenske ◽  
Gerhard Baum
Keyword(s):  
Crystal Structures ◽  
Ion Pairs ◽  
Acetonitrile Solution ◽  
Tungsten Atom ◽  
Acetonitrile Molecule ◽  
Space Group ◽  
Bond Lengths ◽  
Fluoride Ligands ◽  
In Trans ◽  
Alkyne Complexes

Several tungsten alkyne complexes of the type [WCl4(R – C ≡ C – H)]2 and [WCl4(R – C ≡ C — R′)]2 have been prepared by reactions of WCl6 with the alkynes in the presence of C2Cl4. Treating with BrSiMe3 leads to corresponding bromo complexes, whereas reactions of NaF and KF, respectively, in acetonitrile solution in the presence of crown ethers yield the fluoro complexes [Na(15-crown-5)][WF5(R – C ≡ C – R′)] and [K(18-crown-6)][WF5(R – C ≡ C – R ′)], respectively. All complexes were characterized by IR and 13C NMR spectroscopy. The crystal structures of [K(18-crown-6)][WF5(Ph – C ≡ C – H)] · CH3CN and [WCl4(Ph – C ≡ C – Se – n – C4H9)(CH3CN)] have been determined by X-ray methods.[K(18-crown-6)][WF5(Ph – C ≡ C – H] · CH3CN: Space group P21 Z = 2, 8555 observed unique reflections, R = 0.034. Lattice dimensions at -70 °C: a = 1199.4(3), b = 893.4(2), c = 1351.8(3) pm, β = 109.73(3)°. The compound forms ion pairs via three K – F contacts with bond lengths of 262.0, 282.7, and 293.3 pm; the potassium ion is thus nine-fold coordinated by the six oxygen atoms of the crown ether molecule and by three fluoride ligands. The alkyne ligand is bonded side on to the tungsten atom of the [WF5(Ph – Cs ≡ C – H)]- unit with WC bond lengths of 202.4 and 202.6 pm, respectively.[WCl4(Ph – C ≡ C – Se – n – C4H9)(CH3CN)]: Space group P21/a, Z = 4,4595 observed unique reflections, R = 0.058. Lattice dimensions at -70 °C: a = 1030.3(5), b = 1596.3(9), c = 1170.9(7) pm, β = 104.28(3)°. The compound has a molecular structure, in which the tungsten atom is seven-fold coordinated by four chloride ligands, by the two alkyne carbon atoms (WC bond lengths 200 and 203 pm), and in trans position to the latter by the nitrogen atom of the acetonitrile molecule with a W – N bond length of 226 pm.

Acetylenkomplexe von Rhenium(+ VI). Die Kristallstrukturen von [ReCl4(n-C3H7 – C= C – n-C3H7)(POCl3)] und ReCl4(THF)2 / Alkyne Complexes of Rhenium(+VI). The Crystal Structures of [ReCl4(n-C3H7 – C= C – n-C3H7)(POCl3)] and ReCl4(THF)2

1990 ◽  
Vol 45 (9) ◽  
pp. 1227-1234 ◽  
Author(s):  
Hans-Walter Swidersky ◽  
Jürgen Pebler ◽  
Kurt Dehnicke ◽  
Dieter Fenske
Keyword(s):  
Crystal Structure ◽  
Ir Spectroscopy ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Space Group ◽  
Bond Lengths ◽  
In Trans ◽  
Alkyne Complexes ◽  
In Cis ◽  
Ray Methods

The results of the magnetic susceptibility measurements of the previously reported rhenium alkyne complexes [ReCl4(PhC≡CPh)]2.2 CH2Cl2 and [ReCl4(PhC=CPh)(CH3CN)] in the temperature range of 4.2-293 K suggest d1-configurations, corresponding with oxidation state +VI for the rhenium atoms. The new alkyne complex [ReCl4(n-C3H7–C=C–n-C3H7)(POCl3)] has been prepared by the reaction of ReCl5·OPCl3 with n-C3H7-C≡C–n-C3H7 in CCl4 solution, forming dark red single crystals, which were characterized by IR spectroscopy as well as by a crystal structure determination with X-ray methods (space group P2,/c, Z = 4, 3235 observed unique reflexions, R = 0.026; lattice dimensions at –70 °C: a = 805.6(2), b = 1000.6(4), c = 2188.8(6) pm, β = 79.59(2)°). [ReCl4(n-C3H7-C=C–n-C3H7)(POCl3)] has a molecular structure with the alkyne ligand bonded side-on (bond lengths Re-C 198.4 and 198.2(5) pm). The oxygen atom of the solvating POCl3 molecule is coordinated in trans position to the ReC2 unit of the alkyne ligand (bond length Re—O = 223.7(3) pm).In THF solutions the alkyne complexes of this type undergo a slow reaction forming ReCl4(THF)2, which was also characterized by IR spectroscopy and a crystal structure determination (space group P212121, Z = 4, 2243 observed unique reflexions, R = 0.053; lattice dimensions at –70 °C: a = 773.0(14), b = 1267.1(6), c = 1398.6(7) pm). In ReCl4(THF)2 the THF molecules coordinate in cis-position (bond lengths Re–O 208 and 212(1) pm).

scholarly journals Tuning flavin environment to detect and control light-induced conformational switching in Drosophila cryptochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Siddarth Chandrasekaran ◽  
Connor M. Schneps ◽  
Robert Dunleavy ◽  
Changfan Lin ◽  
Cristina C. DeOliveira ◽  
...  
Keyword(s):  
Side Reactions ◽  
Resonance Spectroscopy ◽  
Conformational Switching ◽  
Spin Resonance ◽  
Degradation Activity ◽  
Recognition Motifs ◽  
Cellular Turnover ◽  
Control Light ◽  
Dynamics Simulations ◽  
And Control

AbstractLight-induction of an anionic semiquinone (SQ) flavin radical in Drosophila cryptochrome (dCRY) alters the dCRY conformation to promote binding and degradation of the circadian clock protein Timeless (TIM). Specific peptide ligation with sortase A attaches a nitroxide spin-probe to the dCRY C-terminal tail (CTT) while avoiding deleterious side reactions. Pulse dipolar electron-spin resonance spectroscopy from the CTT nitroxide to the SQ shows that flavin photoreduction shifts the CTT ~1 nm and increases its motion, without causing full displacement from the protein. dCRY engineered to form the neutral SQ serves as a dark-state proxy to reveal that the CTT remains docked when the flavin ring is reduced but uncharged. Substitutions of flavin-proximal His378 promote CTT undocking in the dark or diminish undocking in the light, consistent with molecular dynamics simulations and TIM degradation activity. The His378 variants inform on recognition motifs for dCRY cellular turnover and strategies for developing optogenetic tools.

scholarly journals Environmentally persistent free radicals are ubiquitous in wildfire charcoals and remain stable for years

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Gabriel Sigmund ◽  
Cristina Santín ◽  
Marc Pignitter ◽  
Nathalie Tepe ◽  
Stefan H. Doerr ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Reactive Oxygen ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Pyrogenic Carbon ◽  
Spin Resonance ◽  
Long Time ◽  
High Concentrations

AbstractGlobally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as well as surface fires in forest, shrubland and grassland spanning different boreal, temperate, subtropical and tropical climate. Using electron spin resonance spectroscopy, we measure high concentrations of environmentally persistent free radicals in charcoal samples, much higher than those found in soils. Concentrations increased with degree of carbonization and woody fuels favoured higher concentrations. Moreover, environmentally persistent free radicals remained stable for an unexpectedly long time of at least 5 years. We suggest that wildfire charcoal is an important global source of environmentally persistent free radicals, and therefore potentially of harmful reactive oxygen species.

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