Search results for "Dimer"
showing 10 items of 558 documents
Long- and short-term in vitro D-dimer stability measured with INNOVANCE D-Dimer.
2009
Summary In vitro D-dimer stability in plasma is widely assumed, but has not yet been documented by systematic studies using samples covering a wide range of D-dimer. We investigated the short- and long-term stability of D-dimer in clinical citrated plasma samples with normal and pathological levels. The short-term stability was analysed by measuring D-dimer fresh, after storage of plasma for 4 hours at room temperature (RT) and after an additional 24 h storage at +2 to +8°C (n=40). Long-term stability samples (n=40) were measured fresh and after storage for 19, 25 and 36 months at ≤-60°C. The effect of repeated freezing was analysed by measuring samples (n=50) fresh and after four consecuti…
Synthesis and Electrochemistry of Aluminum Porphycenes. Crystal and Molecular Structure of Methyl-σ-Bonded Aluminum Etioporphycene
1997
The synthesis and characterization of three monomeric aluminum porphycenes with anionic or σ-bonded axial ligands is reported. The investigated compounds are represented as ( EtioPc ) Al ( CH 3) and ( EtioPc ) AlX where EtioPc represents the dianion of etioporphycene and X = Cl − or OH −. Each synthesized complex was characterized by mass spectrometry. 1 H NMR, IR and UV-visible spectroscopies as well as by electrochemistry. Comparisons are made between the properties of complexes in the aluminum etioporphycene series and related chloro- or methyl σ-bonded Al ( III ) porphyrins containing octaethylporphyrin ( OEP ) or tetraphenylporphyrin ( TPP ) macrocycles. Comparisons are also made betw…
Alkane oxidation by a carboxylate-bridged dimanganese(III) complex
2001
[EN] A new manganese( III) oxamato dimer possesing an unprecedented Mn-2(mu -O2CR)(mu -OH2. . .O2CR) core has been synthesised, structurally and magnetically characterised, and used as a catalyst for the oxidation of alkanes to alcohols and ketones by (BuO2H)-O-t and O-2 in CH2Cl2 at rt.
<title>Shallow electron traps in alkali halide crystals: Mollwo-Ivey relations of the optical absorption bands</title>
2001
Evidences are given that two classes of the transient IR- absorption bands: (a) with max. at 0.27-0.36 eV in NaCl, KCl, KBr, KI and RbCl (due to shallow electron traps according G. Jacobs or due to bound polarons according E.V. Korovkin and T.A. Lebedkina) and (b) with max. at 0.15-0.36 eV in NaI, NaBr, NaCl:I, KCl:I, RbCl:I and RbBr:I (due to on-center STE localized at iodine dimer according M. Hirai and collaborators) are caused by the same defect- atomic alkali impurity center [M+]c0e- (electron e- trapped by a substitutional smaller size alkali cation impurity [M+]c0). The Mollwo-Ivey plots (for the transient IR-absorption bands) of the zero-phonon line energy E0 (for NaCl, KCl, KBr, Rb…
Model of the catalyticA+B→0reaction with surface reconstruction
2002
The $A+\stackrel{\ensuremath{\rightarrow}}{B}0$ reaction model with a surface reconstruction is analyzed. It is compared with another similar model for the ${A+1/2B}_{2}\ensuremath{\rightarrow}0$ reaction [V. N. Kuzovkov et al., J. Chem. Phys. 108, 5571 (1998)], which mimics the CO oxidation reaction on the Pt surfaces. The effect of monomer B adsorption instead of dimer ${B}_{2}$ is examined. It is shown that qualitative system features such as reactant concentration oscillations are independent of this substitution.
Dimeric capsules of tetraurea calix[4]arenes. MD simulations and X-ray structure, a comparison
2002
The single crystal X-ray structure of a homodimer of a tetra(tolylurea) calix[4]arene including a tetraethylammonium cation as guest shows an expansion of the capsule and a distortion of its shape, in comparison to the structure of a similar dimer with an encapsulated benzene molecule. Thus, only 8 of 16 possible hydrogen bonds are present in the hydrogen bonded belt holding together the two hemispheres. The encapsulated cation is disordered over two equivalent positions with two methyl groups pointing to the equator, while two methyl groups pointing to the poles form CH–π interactions with the inner surfaces of the calixarene cavities. MD simulations are in agreement with the distorted X-r…
N-[1-(Silatran-1-yl)propyl]pentafluorobenzamide
2007
In the title compound {systematic name: N-[3-(5-aza-2,8,9-trioxa-1-silabicyclo[3.3.3]undecan-1-yl)propyl]pentafluorobenzamide}, C16H19F5N2O4Si, unexpected weak anion⋯π-type C=O⋯C(aromatic) interactions form a dimer [O⋯C distances of 3.096 (3) and 3.036 (3) A]. These dimers are further connected by a normal N—H⋯O hydrogen bond [2.955 (2) A], from the amide H atom to one of the silatrane O atoms. Also, four intermolecular contacts between CH groups and silatrane O and F atoms [3.101(3)–3.406 (3) A] are observed.
Multiple catenanes based on tetraloop derivatives of calix[4]arenes
2009
Abstract Four novel tetraarylurea calix[4]arenes ( 4a – d ) have been synthesized, substituted by ω-alkenyloxy residues in 3,5-positions of the arylurea residues. The eight alkenyl groups were pairwise connected by olefin metathesis and subsequent hydrogenation. The ring-closure reaction was carried out with heterodimers exclusively formed by 4 with a tetratosylurea calix[4]arene 1 , which serves as a template in this reaction step. The potential trans-cavity bridging is entirely suppressed in this way. Bis- and tetraloop calix[4]arenes cannot form dimers due to overlapping loops. However, they readily form heterodimers with open-chain tetraureas, as long as their urea residues can pass thr…
Copper-Assisted Hemiacetal Synthesis: A Cu II Chain Obtained by a One-Step in situ Reaction of Picolinaldehyde
2014
International audience; The 1D polymer complex [Cu2(L)2(SCN)2]n (1 ) has been synthesised in a one‐step in situ reaction of picolinaldehyde with sodium thiocyanate. The complex 1 was characterised by FTIR spectroscopy, UV/Vis spectrophotometry and elemental analysis. The crystal structure of complex 1 shows that chains of dimer complexes are formed with tetra‐ and pentacoordinate copper centres alternately linked by one thiocyanato and two alkoxido bridges. Variable‐temperature magnetic measurements showed a strong antiferromagnetic interaction between the copper centres within the dimer mediated by the two alkoxido bridges with a J value of –374 cm–1, which is in agreement with the DFT‐cal…
New Molecular Topologies by Fourfold Metathesis Reactions within a Hydrogen-Bonded Calix[4]arene Dimer
2003
A calix[4]arene tetrapentyl ether in the cone conformation substituted at its wide rim by four m-(omega-octenyloxy)phenyl urea groups forms hydrogen-bonded dimeric capsules in dichloromethane/benzene (95:5). Metathesis reaction with Grubbs' catalyst under high-dilution conditions (1.1 x 10(-4) M) followed by hydrogenation leads to a covalent connection of all the urea groups within a dimer. Three topologically different products may be expected in such a reaction: a bis[2]catenane, a doubly bridged monocatenane and a tetrabridged capsule. All three possible reaction products could be isolated in an overall yield up to 60 % for the separated and purified compounds. Their identification was b…