Search results for "DECOMPOSITION"
showing 10 items of 766 documents
Standard forms and entanglement engineering of multimode Gaussian states under local operations
2007
We investigate the action of local unitary operations on multimode (pure or mixed) Gaussian states and single out the minimal number of locally invariant parametres which completely characterise the covariance matrix of such states. For pure Gaussian states, central resources for continuous-variable quantum information, we investigate separately the parametre reduction due to the additional constraint of global purity, and the one following by the local-unitary freedom. Counting arguments and insights from the phase-space Schmidt decomposition and in general from the framework of symplectic analysis, accompany our description of the standard form of pure n-mode Gaussian states. In particula…
Correlation between the molecular structure and the kinetics of decomposition of azamacrocyclic copper(II) complexes
2015
The formation of copper(II) complexes with symmetrical dinucleating macrocyclic ligands containing two either monomethylated (L1) or trimethylated (L2) diethylenetriamine (Medien or Me3dien) subunits linked by pyridine spacers has been studied by potentiometry. Potentiometric studies show that L1 has larger basicity than L2 as well as higher stability of its mono- and binuclear complexes. The crystal structures of L1·6HCl (1), [Cu2(L1)Cl2](CF3SO3)2 (2), [Cu2(L1)(OH)](ClO4)3·3H2O (3) and [Cu(L1)](ClO4)2 (4) show that L1 adopts different coordination modes when bound to copper(II). Whereas in 2, each copper(II) is bound to one Medien subunit and to one pyridine group, in 3 each metal center i…
Selenium Imides: 77Se NMR Investigations of the SeCl2−tBuNH2 Reaction and X-ray Structures of Se3(NtBu)3, tBuNSe(μ-NtBu)2SO2, and tBuNSe(μ-NtBu)2SeO
2000
The reaction of SeCl2 with tert-butylamine in various molar ratios in THF at −78 °C has been investigated by 77Se NMR spectroscopy. In addition to the known Se−N heterocycles Se6(NtBu)2 (1) and Se9(NtBu)6 (2), the acyclic imidoselenium(II) dichlorides ClSe[N(tBu)Se]nCl (4, n = 1; 5, n = 2) and two new cyclic selenium imides [Se3(NtBu)2]n (3, n = 1 or 2) and Se3(NtBu)3 (6) have been isolated and identified. An X-ray analysis shows that 6 is a six-membered ring in a chair conformation with |d(Se−N)| = 1.833 A. Crystal data: 6, trigonal, P3c1, a = 9.8660(3) A, c = 20.8427(7) A, V = 1757.0(1) A3, Z = 6. The 1H, 13C, and 77Se NMR data for 1−6 are reported, and some reassignments of earlier lite…
Synthesis and Reactivity toward Isonitriles of (2-Aminoaryl)palladium(II) Complexes
2001
Mixtures of “Pd(dba)2” (dba = dibenzylideneacetone) and 2,2‘-bipyridine (bpy; 1:2) or N,N,N‘,N‘-tetramethylethylenediamine (tmeda; 1:1) react with 2-bromo-4-nitroaniline to give [Pd{C6H3NH2-2-NO2-5}Br(N−N)] (N−N = bpy (1b), tmeda (1b‘)). Reactions of 2-iodoaniline with mixtures of “Pd(dba)2” and isonitriles RNC (R = C6H3Me2-2,6 (Xy), 2:1:2 molar ratios; R = tBu, 2.9:1:2 molar ratios) result in the formation of the complexes [Pd{κ2C,N-C(NXy)C6H4NH2-2}I(CNXy)] (2a) and trans-[Pd{C(NtBu)C6H4NH2-2}I(CNtBu)2] (3a*). The reactions of [Pd{C6H4NH2-2}I(bpy)] and 1b‘ with RNC give the complexes trans-[Pd{C(NR)C6H3NH2-2-Y-5}}X(CNR)2] (Y = H, X = I, R = Xy (3a), tBu (3a*); Y = NO2, X = Br, R = Xy (3b),…
Coordination properties of imino(2-pyridyl)methylpalladium(II) compounds. Preparation and thermal rearrangement of binuclear adducts with palladium(I…
1988
Abstract The imino(2-pyridyl)methylpalladium(II) compound py-2-C(R′)NR (R = C 6 H 4 OMe-p, R′ = trans-PdCl(PPh 3 ) 2 ) reacts with [PdCl 2 (CH 2 CHPh)] 2 , [PdCl 2 - (NCMe) 2 ], and K[PtCl 3 (CH 2 CH 2 )] to give binuclear complexes [MCl 2 {py-2- C(R′)NR}] (M = Pd, Pt), in which the α-diimino group acts as a chelating bidentate ligand. In hot 1,2-dichloroethane, these complexes undergo a PPh 3 and chloride ligand exchange at rates which depend markedly on the metal M (Pd ⪢ Pt), to yield the new derivatives [MCl(PPh 3 ){py-2-C(cis-PdCl 2 (PPh 3 ))NR}]. The ligand exchange is followed by a much slower decomposition to [MCl 2 (PPh 3 ) 2 ]. Labile intermediates of the same type, [MCl(PPh …
Pyrimido[5,4-c]pyrrolo[2,1-a]isoquinoline: a new potential DNA-interactive ring system
2003
The acid catalyzed decomposition of the azide 9 failed to give the title compounds, which were however obtained by a Pschorr-type cyclization on reactive 1-(6-aminopyrimidin-5-yl)-pyrroles of type 13. Derivatives of type 14 and 15 were fully characterized by NMR data. Theoretical calculations demonstrated that the new compounds possess properties suitable for DNA- intercalation.
Geometric isomeric pairs: synthesis, structure, thermal decomposition and magnetic properties of cis- and trans-[Cr(mal)(bpy)(H2O)2][NO3]·xH2O (H2mal…
2001
Abstract Procedures are given for the preparation and isolation of cis-[Cr(mal)(bpy)(H2O)2][NO3]·3H2O (I) and trans-[Cr(mal)(bpy)(H2O)2][NO3]·H2O (II) (H2mal=malonic acid, bpy=2,2′-bipyridine). The single crystals X-ray structure of cis-compound reveals that the cations and anions as well as cations between cations are linked into hydrogen-bonded chains. Unfortunately, little structural information is available for the trans compound II (only isotropic cation refinement), nevertheless, from this result is observed that there also exists a hydrogen-bonded network between anion units. Thermal analysis and magnetic behaviour for both compounds were studied.
(Z)- und (E)-Enole von diarylsubstituierten β-Ketocarbonsäurederivativen
2006
(Z) and (E) Enols of Diaryl-Substituted β-Ketocarboxylic Acid Derivatives Thermolysis of the 1,3-diaryl-2-diazo-1,3-propanediones 4 in the presence of alcohols or amines yielded the compounds 7–11 which exist as chelated (Z) enols or as tautomeric ketones. Contrary to the steric interaction of two mesityl groups the steric interaction between two naphthyl or two anthryl groups or between naphthyl and mesityl is not sufficient to stabilize the corresponding (E) enols. The latter isomers were generated in irradiation processes of some (Z) enols. Detailed NMR studies were performed in order to characterize the enols and their molecular dynamics.
Melting behaviour of d-sucrose, d-glucose and d-fructose
2004
The melting behaviour of d-sucrose, d-glucose and d-fructose was studied. The melting peaks were determined with DSC and the start of decomposition was studied with TG at different rates of heating. In addition, melting points were determined with a melting point apparatus. The samples were identified as d-sucrose, alpha-d-glucopyranose and beta-d-fructopyranose by powder diffraction measurements. There were differences in melting between the different samples of the same sugar and the rate of heating had a remarkable effect on the melting behaviour. For example, T(o), DeltaH(f) and T(i) (initial temperature of decomposition) at a 1 degrees Cmin(-1) rate of heating were 184.5 degrees C, 126…
Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition p…
2010
The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition…