Search results for "Racemic mixture"

Chiral and Racemic Spin Crossover Polymorphs in a Family of Mononuclear Iron(II) Compounds

2017

[EN] Understanding the origin of cooperativity and the equilibrium temperature of transition (T1/2) displayed by the spin-crossover (SCO) compounds as well as controlling these parameters are of paramount importance for future applications. For this task, the occurrence of polymorphism, presented by a number of SCO complexes, may provide deep insight into the influence of the supramolecular organization on the SCO behavior. In this context, herein we present a novel family of mononuclear octahedral FeII complexes with formula cis- [Fe(bqen)(NCX)2], where bqen is the chelating tetradentate ligand N,N¿-bis(8-quinolyl)ethane-1,2-diamine and X = S, Se. Depending on the preparation method, these…

Synthesis and structural properties of hexaaza[5]helicene containing two [1,2,3]triazolo[1,5-a]pyridine moieties

2013

Abstract We have synthesized a novel hexaaza[5]helicene in a straightforward way from neocuproine. The crystal structure has been elucidated with direct-space strategy TALP which demonstrates the power of the powder X-ray diffraction technique. In this crystal structure it is possible to see an interplanar angle of 33(1)° between the two triazolopyridine rings. The centrosymmetric crystal structure is a racemic mixture, but the resolution was not possible due to a ring-chain isomerization in a solution that produces a dynamic racemization.

The enantiomers of phenprocoumon: pharmacodynamic and pharmacokinetic studies.

1976

The pharmacodynamics and pharmacokinetics of the optical enantiomers of phenprocoumon were studied in 5 normal subjects and compared to the racemic mixture. Each subject received a single oral dose of 0.6 mg/kg of racemic, S(-), and R(+) phenprocoumon. S(-) phenprocoumon was 1.6 to 2.6 times as a potent as R(+) phenprocoumon when the area under the effect/time curve was used to quantify the total anticoagulant effect per dose. Comparing the plasma concentrations that elicited the same anticoagulant effect, S(-) phenprocoumon was 1.5 to 2.5 times as potent as R(+) phenprocoumon. The anticoagulant activity of the racemic mixture was between that of the enantiomers. There was no distinct diffe…

PHOSPHORORGANISCHE VERBINDUNGEN 931

1980

Abstract Optisch aktives Ethyl-phenyl-phosphinigsaurediethylamid 1 wird in racemische literaturbekannte Verbindungen uber-gefuhrt bei der Einwirkung von HCl, HBF4, Alkoholen, Thioalkoholen, Carbonsauren, Carbonsaureestern, Carbonsaureanhydriden, Carbonsaurehalogeniden, Verbindungen mit Pl und sekundaren Phosphinen. p-Kresol, Trifluoressigsaure-p-kresylester sowie Trifluoressigsaure-s,s,s-trifluorethylester setzen sich mit optisch aktivem Ethyl-phenyl-phosphinigsaure-diethylamid 1 unter Erhaltung der Konfiguration zu den entsprechenden optisch aktiven Ethyl-phenyl-phosphingsaureestern um. Optically active ethyl-phenyl-phosphinous acid diethylamide 1 was treated with HCl, HBF4, alcohols, thio…

Subcomponent self‐assembly of a cyclic tetranuclear Fe(II) helicate in a highly diastereoselective self‐sorting manner

2019

Abstract An enantiomerically pure diamine based on the 4,15‐difunctionalized [2.2]paracyclophane scaffold and 2‐formylpyridine self‐assemble into an optically pure cyclic metallosupramolecular Fe4L6 helicate upon mixing with iron(II) ions in a diastereoselective subcomponent self‐assembly process. The cyclic assembly results from steric strain that prevents the formation of a smaller linear dinuclear triple‐stranded helicate, and hence, leads to the larger strain‐free assembly that fulfils the maximum occupancy rule. Interestingly, use of the racemic diamine also leads to a racemic mixture of the homochiral cyclic helicates as the major product in a highly diastereoselective narcissistic ch…

A new BEDT-TTF salt and polypyrrole films containing the chiral polyoxometalate [H4Co2Mo10O38]6−

2005

Abstract The chiral polyoxometalate [H4Co2Mo10O38]6− has been used in the preparation of hybrid materials in the form of crystals or polymeric films. A new radical salt of the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) containing the two enantiomers of this polyoxometalate has been obtained by electrocrystallization. This radical salt shows semiconducting behavior with room temperature conductivity of 9 S.cm−1 and activation energy of 40 meV. Polypyrrole films doped with a racemic mixture of polyoxometalates and also the enantiomerically pure (+)589-[H4Co2Mo10O38]6− have been prepared electrochemically. Circular dichroism experiments suggest that the chiral polyoxometalate…

Enantiomer separation by chiral-phase liquid chromatography of urethane derivatives of natural diacylglycerols previously fractionated by reversed-ph…

1991

Abstract Enantiomers of diacylglycerols such as 3,5-dinitrophenyl isocyanate (urethane) derivatives previously fractionated by reversed-phase high-performance liquid chromatography (HPLC) were separated by HPLC on a chiral phase column [N-( R )-1-(α-naphthyl)ethylamino-carbonyl-( S )-valine chemically bound to γ-aminopropylsilanized silica]. In addition to the separation of commercial monoacid-diacylglycerol isomers, separation of diacid-diacylglycerol isomers obtained from peanut oil and cottonseed oil triacylglycerols by chemical hydrolysis is reported. Hexane-ethylene dichloride-ethanol mixtures were used for elution of the diacylglycerol derivative isomers, which were detected by their …

Adamantan als Baustein neuer Araliphane Synthese, Spektroskopie und Kristallstrukturen

1991

Adamantane as a Building Block of New Araliphanes – Synthesis, Spectroscopy, and Crystal Structures Exchange of benzene units for aliphatic building blocks in cyclophanes leads to new molecules of the “araliphane” type. With adamantane the araliphanes 2 – 4 are synthesized. Their stereochemical behavior as shown by NMR studies and X-ray crystallographic analyses differs significantly from that of their aromatic counterparts. The signals of the intraannular adamantane hydrogens are strongly shifted upfield up to δ=– 2.18 (in 2). 4 is obtained as a racemic mixture of enantiomers (in the crystalline state) and shows a boat-like deformation of the benzene moiety.

The effects of racemic bethanechol and its (R)- and (S)-enantiomers on pre- and postjunctional muscarine receptors in the guinea-pig ileum

1985

The effect of racemic bethanechol and its (R)- and (S)-enantiomers on smooth muscle contraction and outflow of [3H]-acetylcholine were studied in the guinea-pig myenteric plexus-longitudinal muscle preparation that had been preincubated with [3H]-choline. (S)-, racemic, and (R)-bethanechol caused concentration-dependent contractions of the longitudinal muscle. The potency ratio of the strong isomer (S) to the weak one (R) was 915. Racemic and (S)-bethanechol concentration-dependently inhibited the evoked outflow of [3H]-acetylcholine. Racemic bethanechol was more potent than (S)-bethanechol. (R)-bethanechol up to a concentration of 1 mM did no affect the evoked outflow of [3H]-acetylcholine…

2016

Despite hundreds of cationic bis-cyclometalated iridium(III) complexes having been explored as emitters for light-emitting electrochemical cells (LEECs), uniformly their composition has been in the form of a racemic mixture of Λ and Δ enantiomers. The investigation of LEECs using enantiopure iridium(III) emitters, however, remains unprecedented. Herein, we report the preparation, the crystal structures, and the optoelectronic properties of two families of cyclometalated iridium(III) complexes of the form of [(C^N)2Ir(dtBubpy)]PF6 (where dtBubpy is 4,4′-di-tert-butyl-2,2′-bipyridine) in both their racemic and enantiopure configurations. LEEC devices using Λ and Δ enantiomers as well as the r…