Search results for " NMR spectroscopy"
showing 10 items of 70 documents
Isolation of enantiomerically pure organometallic palladium compounds: synthesis of the triangles prepared from enantiopure [cis-Pd2(C6H4PPh2)2(NCCH3…
2009
Reaction of the racemic [Pd(C(6)H(4)PPh(2))Br](4) () with the silver salt of 1R-(1alpha,2beta,3alpha)]-3-methyl-2-(nitromethyl)-5-oxocyclopentaneacetate, (R)-AgO(2)CR*, results in the formation of a mixture of diastereoisomers (RRR)- and (SRR)- of the formula Pd(2)(C(6)H(4)PPh(2))(2)(O(2)CR*)(2) that were separated by standard chromatographic methods. Each diastereoisomer was readily converted into the tetrametallic stereoisomers (SS)- and (RR)-, of the formula [Pd(C(6)H(4)PPh(2))Br](4) that were isolated and characterized by X-ray crystallography. The R enantiomer of the solvated cationic species [cis-Pd(2)(C(6)H(4)PPh(2))(2)(NCCH(3))(4)](2+), obtained from (RR)-, was reacted with ammonium…
Synthesis of a New pH-Dependent Ligand: Conformational and Complexation Studies
2003
A new macrocyclic ligand, 3, which exhibits pH-induced conformational changes, has been prepared. This ligand consists of a crown ether derived from a trans-anti-trans 1,2,4,5-tetrasubstituted cyclohexane. Due to the stereochemistry of the substituents on the carbocyclic ring, two different low-energy conformations of the crown ether are possible. Ligand 3 has been studied in solution by 1H NMR spectroscopy at different values of pH and temperature, showing that the conformation of the crown ether, and thus its complexing ability, is strongly pH-dependent. The solid-state structure of the ligand has been determined by X-ray diffraction.
Structure of a polysaccharide from the lipopolysaccharide of Vibrio vulnificus clinical isolate YJ016 containing 2-acetimidoylamino-2-deoxy-L-galactu…
2009
Abstract A polysaccharide isolated after mild acid degradation of the lipopolysaccharide of Vibrio vulnificus clinical isolate YJ016 was found to contain l -Fuc, d -GlcpNAc, 2,4-diacetamido-2,4,6-trideoxy- d -glucose (di-N-acetylbacillosamine, d -QuiNAc4NAc), and 2-acetimidoylamino-2-deoxy- l -galacturonic acid ( l -GalNAmA). The last sugar derivative was confirmed by correlations for nitrogen-linked protons in 2D TOCSY and ROESY spectra measured in a H2O–D2O mixture. The following structure of the polysaccharide was established by 1H and 13C NMR spectroscopy, including 2D ROESY and 1H,13C HMBC experiments: Download : Download full-size image where the degree of 6-O-acetylation of the later…
Binding and Fluorescent Sensing of Dicarboxylates by a Bis(calix[4]pyrrole)-Substituted BODIPY Dye
2013
A bis(calix[4]pyrrole)-substituted BODIPY ditopic receptor 1 has been synthesised and characterised. The binding and sensing properties of 1 towards several aliphatic and aromatic dicarboxylates have been evaluated by using UV/Vis fluorescence and 1H NMR spectroscopy. The receptor strongly binds linear α,ω-dicarboxylates of appropriate lengths (C9 and C10) by acting as a cleft. For all dicarboxylates, the binding event is detected by a bathochromic shift in the UV/Vis spectra of the receptor and by strong quenching of its fluorescence.
On the mechanistic behavior of highly efficient palladium-tetraphosphine catalytic systems for cross-coupling reactions: first spectroscopic and elec…
2008
Electrochemical studies carried out in conjunction with 31P NMR spectroscopy on the palladium(II)/palladium(0) halogeno complexes of the tetraphosphine 1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di...
Host-Guest Interactions of Sodiumsulfonatomethyleneresorcinarene and Quaternary Ammonium Halides : An Experimental-Computational Analysis of the Gues…
2020
The molecular recognition of nine quaternary alkyl- and aryl-ammonium halides (Bn) by two different receptors, Calkyl-tetrasodiumsulfonatomethyleneresorcinarene (An), were studied in solution using 1H NMR spectroscopy. Substitution of methylenesulfonate groups at 2-positions of resorcinol units resulted in an increase of cavity depth by ∼2.80 Å and a narrow cavity aperture compared to Calkyl-2-H-resorcinarenes. The effect of alkyl chain lengths on the endo-complexation, that is the ability to incorporate other than N-methyl chains inside the cavities, were investigated using ammonium cations of the type ⁺NH2(R1)(R2), (R1 = Me, Et, Bu, R2 = Bu, Ph, Bz ). The C−H⋯ interactions between guests …
Geminal Ionic Liquids: A Combined Approach to Investigate their Tridimensional Structure
2009
Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3’-di-n-butyl-1,1’-(1,3- phenylenedimethylene)diimidazolium and 3,3’-di-n-butyl-1,1’-(1,4-phenylenedimethylene) diimidazolium bis- ACHTUNGTRENUNG[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different sha…
Structure ofD-ribonic acid-dimethyltin(IV) in coordinating solvents: an experimental and DFT119Sn NMR study
2006
We have investigated a newly synthesized complex of D-ribonic acid with dimethyltin(IV). The structure of the complex in solution has been characterized by means of 1 H, 13 C, and 119 Sn NMR and by DFT calculations. The comparison of experimental and computational results allowed the determination of the stable conformation in solution as well as the detection of a dimerization process. Moreover, evidence is given of active coordination of the metal by the solvent.
Polysubstituted ferrocenes as tunable redox mediators
2018
A series of four ferrocenyl ester compounds, 1-methoxycarbonyl- (1), 1,1’-bis(methoxycarbonyl)- (2), 1,1’,3-tris(methoxycarbonyl)- (3) and 1,1’,3,3’-tetrakis(methoxycarbonyl)ferrocene (4), has been studied with respect to their potential use as redox mediators. The impact of the number and position of ester groups present in 1–4 on the electrochemical potential E1/2 is correlated with the sum of Hammett constants. The 1/1+–4/4+ redox couples are chemically stable under the conditions of electrolysis as demonstrated by IR and UV–vis spectroelectrochemical methods. The energies of the C=O stretching vibrations of the ester moieties and the energies of the UV–vis absorptions of 1–4 and 1+–4+ c…