Search results for "x-ray structure"
showing 10 items of 32 documents
[2,6-Bis(di-tert-butylphosphinomethyl)phenyl-κ3P,C1,P′](trifluoroacetato)palladium(II)
2010
The Pd(II) atom in the title compound, [Pd(C(2)F(3)O(2))(C(24)H(43)P(2))], adopts a distorted square-planar geometry with the P atoms in a trans arrangement, forming two five-membered chelate rings. Four intra-molecular C-H⋯O hydrogen bonds occur. The crystal packing reveals one weak inter-molecular C-H⋯O hydrogen bond, which self-assembles the mol-ecules into infinite chains parallel to the b axis.
Revised structure of trans-resveratrol: Implications for its proposed antioxidant mechanism
2015
The crystal structure of trans-resveratrol has been redetermined by X-ray diffraction. The newly refined structure demonstrates that the previously reported, dynamically disordered hydrogen-bonding network is rather the superposition of two crystallographically independent molecules of trans-resveratrol. This latter arrangement possesses a well-defined hydrogen-bonding network in a unit cell of double the previously reported volume. While not meant as a criticism of the proposed antioxidant mechanism itself, the present studies clearly show that the X-ray diffraction data should no longer be used for its additional support.
Insights into functional aspects of centrins from the structure of N-terminally extended mouse centrin 1
2006
AbstractCentrins are members of the family of Ca2+-binding EF-hand proteins. In photoreceptor cells, centrin isoform 1 is specifically localized in the non-motile cilium. This connecting cilium links the light-sensitive outer segment with the biosynthetic active inner segment of the photoreceptor cell. All intracellular exchanges between these compartments have to occur through this cilium. Three-dimensional structures of centrins from diverse organisms are known, showing that the EF-hand motifs of the N-terminal domains adopt closed conformations, while the C-terminal EF-hand motifs have open conformations. The crystal structure of an N-terminally extended mouse centrin 1 (MmCen1-L) resemb…
Elucidating the catalytic reaction mechanism of orotate phosphoribosyltransferase by means of X-ray crystallography and computational simulations
2020
15 p.-8 fig.-2 tab.1 graph. abst.+ 8 fig. supl.-1 tab. supl.
DFT and experimental studies on structure and spectroscopic parameters of 3,6-diiodo-9-ethyl-9H-carbazole
2015
The first report on crystal and molecular structure of 3,6-diiodo-9-ethyl-9H-carbazole is presented. Experimental room-temperature X-ray and 13C chemical shift studies were supported by advanced theoretical calculations using density functional theory (DFT). The 13C nuclear magnetic shieldings were predicted at the non-relativistic and relativistic level of theory using the zeroth-order regular approximation (ZORA). Theoretical relativistic calculations of chemical shifts of carbons C3 and C6, directly bonded to iodine atoms, produced a reasonable agreement with experiment (initial deviation from experiment of 44.3 dropped to 4.25 ppm). The changes in ring aromatic character via simple harm…
Molecular modeling and experimental studies on structure and NMR parameters of 9-benzyl-3,6-diiodo-9H-carbazole
2015
A combined experimental and theoretical study has been performed on 9-benzyl-3,6-diiodo-9H-carbazole. Experimental X-ray (100.0 K) and room-temperature 13C NMR studies were supported by advanced density functional theory (DFT) calculations. The non relativistic structure optimization was performed and the 13C nuclear magnetic shieldings were predicted at the relativistic level of theory using the Zeroth Order Regular Approximation (ZORA). The changes in the benzene and pyrrole rings compared to the unsubstituted carbazole or the parent molecules were discussed in terms of aromaticity changes using the harmonic oscillator model of aromaticity (HOMA) and the nucleus independent chemical shift…
Single ion magnet behaviour in a two-dimensional network of dicyanamide-bridged cobalt(II) ions
2015
A novel two-dimensional coordination polymer of the formula [Co(dca)2(atz)2]n (1) resulted from assembling trans-bis(2-amino-1,3,5-triazine)cobalt(II) motifs by dicyanamide spacers. Variable-temperature dc and ac magnetic susceptibility measurements of 1 show that the high-spin cobalt(II) ions act as single ion magnets (SIMs).
Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin
2017
The enantioselectivity of β-cyclodextrin (β-CD) towards L- and D-N-acetyltryptophan (NAcTrp) has been studied in aqueous solution and the crystalline state. NMR studies in solution show that β-CD forms complexes of very similar but not identical geometry with both L- and D-NAcTrp and exhibits stronger binding with L-NAcTrp. In the crystalline state, only β-CD–L-NAcTrp crystallizes readily from aqueous solutions as a dimeric complex (two hosts enclosing two guest molecules). In contrast, crystals of the complex β-CD–D-NAcTrp were never obtained, although numerous conditions were tried. In aqueous solution, the orientation of the guest in both complexes is different than in the β-CD–L-NAcTrp …
Synthesis of new half sandwich tetrachloro derivatives of molybdenum(V) and tungsten(V). X-ray structures of (C5HPri4)W(CO)3(CH3) and (C5Et5)WCl4
2002
International audience; The new synthetic intermediates (Ring)MCl4 [Ring=C5HPri4 or 4Cp, M=Mo, 2; Ring=C5Et5 or VCp, M=W, 4, Ring=4Cp, M=W, 6] containing sterically protecting cyclopentadienyl ligands have been synthesized. Along the synthetic pathway to 2, it was found that the treatment of [4CpMo(CO)3]− with an aqueous ferric solution according to the well established Manning procedure affords the hydride compound 4CpMo(CO)3H (1) by hydrolysis rather than the expected neutral dimer by oxidation. Compound 1 could be converted, however, to 2 upon oxidation with PhICl2 in good yields. Compound 4 is shown by a single crystal X-ray analysis to adopt a monomeric four-legged piano stool structur…
Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)
2000
International audience; The thermal decarbonylation of (Ring)WX3(CO)2 in refluxing toluene has led to the preparation of the CO-free compounds [(Ring)WX3]2 [Ring=η5-C5H5 (Cp) and X=Cl (1a) or Br (1b); Ring=η5-C5H4Me (Cp′), X=Cl (2a) or Br (2b); Ring=η5-C5Me5 (Cp*), X=Cl (3)]. The NMR properties of these molecules are consistent with diamagnetism and thereby indicate a different structure from that of the paramagnetic molybdenum analogues. Compounds 1a and 2a react with dppe to afford mononuclear 18-electron adducts, (Ring)WCl3(dppe) (Ring=Cp (4) or Cp′ (5)). The X-ray structure of 5 shows a pseudo-fac-octahedral geometry with the dppe ligand occupying two equatorial (e.g. cis relative to Cp…