Search results for " database"
showing 10 items of 684 documents
Synthesis and spectroscopic studies (Mo¨ssbauer, IR and NMR) of [R2SnCl2bipym] (R = butyl or phenyl) and the crystal and molecular structure of [Ph2S…
1994
Abstract The complexes [R 2 SnCl 2 bipym] (R = phenyl or butyl, bipym = 2,2′,6,6′-bipyrimidine) were synthesized and studied in solution by 1 H- and 13 C-NMR spectroscopy and in the solid state by IR and Mo¨ssbauer spectroscopy. The latter was also performed in frozen ethanolic solution. The structure of the phenyl complex was determined by single crystal diffraction methods. The value obtained for the angle C-SN-C in the phenyl compound is 169.3(2)° (X-ray) and 151° (Mo¨ssbauer), but the assignment of an octahedral configuration by Mo¨ssbauer spectroscopy is consistent with the structure determined by diffraction. The butyl complex is also octahedral and the two techniques show better agre…
Chemically driven phase separation in black lipid membranes and its coupling to membrane functions
1992
Abstract We analysed the single-channel current fluctuations of gramicidin in bimolecular lipid membranes in order to demonstrate (i) the influence of protein binding to the lateral organisation of a mixed membrane, and (ii) how this couples to the function of the ionophore. Examples of phase separations induced by synthetic polyelectrolytes, as models for peripheral membrane proteins, and specific ligand-receptor interactions are presented and discussed in view of the important lateral order-function relationship in biomembranes.
Über polyplumbane
1985
Abstract Diplumbanes Pb 2 R 3 R′ 3 (R,R′ = Ph, o -Tol, p -Tol) have been synthesized from R 3 PbLi and R′ 3 PbCl at −60°C in THF. Mass, 13 C and 207 Pb NMR spectra of the products exhibit migrations of R, R′ in the transition state (R 3 PbLi + ClPbR′ 3 ) leading to a complex distribution of the substituents (δ( 207 Pb) with respect to PbMe 4 −70 to −95 ppm). The PbPb stretching vibration (100 to 115 cm −1 ) couples with a lattice vibration giving rise to a single intensive Raman line. The crystal structure of Pb 2 Ph 3 ( p -Tol) 3 has been determined and refined to R = 0.155. Two independent molecules are disordered and have identical distribution of the substituents Ph( p -Tol) 2 PbPbPh …
Precursors of aza-macrocycles: Characterization of substituted phenanthrolines and related bases. Crystal and molecular structure of dichloro-d i-n-b…
1993
The synthesis, characterization and 1~ NMR spectra of some substituted 1,lO-phenantrolines are described. These are precursors of azacyclophanes which are, along with their metal complexes, insoluble in polar solvents. It is suggested that the use of substituted 2,2’, 6,6’ -bipyrimidines as precursors would lead to soluble macrocycles. The crystal and molecular structure of dichloro-di-n-butyl(2,2’,6,6’-bipyr
Coordination properties of imino(2-pyridyl)methylpalladium(II) compounds. Reactions with the chloride-bridged allyl dimers [MCl(η3-2-MeC3H4)]2 (MPd,…
1990
Abstract The imino(2-pyridyl)methylpalladium(II) compounds py-2-CR 1 NR [R 1 = trans -PdCl(PPh 3 ) 2 , R = C 6 H 4 OMe- p ( Ia ), Me ( Ib ), CMe 3 ( Ic ); R 1 = Pd(dmtc)(PPh 3 ), R = C 6 H 4 OMe- p ( Id )] react with [MCl(η 3 - 2-MeC 3 H 4 )] 2 (M = Pd, Pt) in a molar ratio 1/0.5 and in the presence of NaClO 4 to yield the binuclear cationic complexes II , [M(η 3 -2-MeC 3 H 4 )(py-2-CR 1 NR)]ClO 4 , where the α-diimino group acts as σ,σ N , N ′ chelating ligand. In the absence of NaClO 4 and with a molar ratio 1/1, the reaction leads initially to formation of a ionic intermediate A , [M(η 3 - 2-MeC 3 H 4 )(py-2-CR 1 NR)] [MCl 2 (η 3 -2-MeC 3 H 4 )], which subsequently undergoes exchange …
Design, synthesis and spectral studies of novel bile acid-arene conjugates: Trans to cis isomerization of azobenzene core controlled by bile acid hyd…
2008
Abstract Four bile acid-arene conjugates, 1,4-bis[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene dibromide ( 1 ), 1,3,5-tris[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene tribromide ( 2 ), bis{4-[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide ( 3 ), and bis{4-[dimethyl(3α-hydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide ( 4 ), have been synthesized in good yields, and their structures have been characterized by 1 H, 13 C, 13 C DEPT-135, PFG 1 H, 13 C HMQC, PFG 1 H, 13 C HMBC, and PFG 1 H, 15 N HMBC NMR spectra. Their molecular weights and elemental compositions have…
"Through-space" 31P spin-spin couplings in ferrocenyl tetraphosphine coordination complexes: improvement in the determination of the distance depende…
2008
Abstract From the analysis of several nickel and palladium halide complexes of a constrained ferrocenyl tetraphosphine, the existence in solution phase of unique 31P–31P “through-space” nuclear spin–spin coupling constants (JPP) had been previously evidenced. Due to the blocked conformation of the species in solution, and based on the NMR spectra obtained for the complexes and their corresponding solid state X-ray structures, these JPP constants had been shown to clearly depend on the mutual spatial position of the corresponding phosphorus atoms. Herein, the quantitative correlation disclosed at that time (P⋯P distance dependence of coupling constants) is remarkably confirmed, and mathemati…
Substituent effects of1H NMR parameters of chlorinated diphenyl ethers. A statistical approach
1994
The 1H NMR spectra of 64 polychlorinated diphenyl ethers (PCDEs) were measured and assigned. Multiple linear regression analysis was used to estimate the effects of chlorine atoms on the 1H NMR chemical shifts and coupling constants. The ‘simple sum rules’ were found to be inadequate for the prediction of 1H NMR chemical shifts of PCDEs. Therefore, corrective terms of two chlorine atoms were taken into account. The most important effects on chemical shifts were shown to be the steric interactions of two adjacent chlorine atoms and the intramolecular ring current effect observed in the ortho-proton of tri-ortho-substituted PCDEs. The substituent effects on J(HH) coupling constants were found…
Spectroscopic and conformational properties of size-fractions separated from a lignite humic acid
2007
Abstract A lignite humic acid (HA) was fractionated by preparative high performance size-exclusion chromatography (HPSEC) in seven different size-fractions. The size-fractions were characterized by cross polarization (CP) magic angle spinning (MAS) 13 C NMR spectroscopy and a further analytical HPSEC elution under UV and fluorescence detection. The alkyl hydrophobic components mainly distributed in the largest molecular-size-fraction, whereas the amount of oxidized carbons increased with decreasing size of fractions. Cross polarization time ( T CH ) and proton spin-lattice relaxation time in the rotating frame ( T 1 ρ (H)) were measured from variable contact time (VCT) experiments. The bulk…
Talking Blockchains: The Perspective of a Database Researcher
2021
There are few topics out there, that seem to create as much confusion and discussion as blockchains. This has a multitude of reasons: (1) A large number of drastically different concepts and systems are unified under the very broad term "blockchain". (2) The topic touches a variety of different fields, including databases, distributed processing, networks, cryptography, and even economics. (3) There exists a large number of different applications of the technology.The goal of this paper is to simplify and structure the discussion of blockchain technology. We first introduce a simple formalization of the basic components, that appear again and again in a variety of blockchain systems. Second…