Search results for "Nuclear magnetic resonance spectroscopy"
showing 10 items of 843 documents
Influence of Amorphous TiO2-x on Titania Nanoparticle Growth and Anatase-to-Rutile Transformation
2012
Amorphous TiO2-x formed together with precursors and anatase nuclei, during TiCl4 hydrolysis at soft conditions, influences both crystal growth and phase stability. The highly defective nanoparticles of anatase grow by reaction of their basic hydroxyls with acidic ones of TiO2 precursor species. The growth of anatase crystals, however, is affected by their interactions with simultaneously formed amorphous TiO2-x which increasingly covers the particles hindering the anatase-precursor contact. The interactions among anatase and amorphous and precursor components have been studied by H-1-MAS (magic angle spinning) NMR spectroscopy. The interaction between acid and basic hydroxyls favors the fo…
Simultaneous endo and exo Complex Formation of Pyridine[4]arene Dimers with Neutral and Anionic Guests
2017
The formation of complexes between hexafluorophosphate (PF6- ) and tetraisobutyloctahydroxypyridine[4]arene has been thoroughly studied in the gas phase (ESI-QTOF-MS, IM-MS, DFT calculations), in the solid state (X-ray crystallography), and in chloroform solution (1 H, 19 F, and DOSY NMR spectroscopy). In all states of matter, simultaneous endo complexation of solvent molecules and exo complexation of a PF6- anion within a pyridine[4]arene dimer was observed. While similar ternary complexes are often observed in the solid state, this is a unique example of such behavior in the gas phase.
NMR Spectroscopic Evidence for the Intermediacy of XeF3− in XeF2/F− Exchange, Attempted Syntheses and Thermochemistry of XeF3− Salts, and Theoretical…
2010
The existence of the trifluoroxenate(II) anion, XeF(3)(-), had been postulated in a prior NMR study of the exchange between fluoride ion and XeF(2) in CH(3)CN solution. The enthalpy of activation for this exchange, ΔH(⧧), has now been determined by use of single selective inversion (19)F NMR spectroscopy to be 74.1 ± 5.0 kJ mol(-1) (0.18 M) and 56.9 ± 6.7 kJ mol(-1) (0.36 M) for equimolar amounts of [N(CH(3))(4)][F] and XeF(2) in CH(3)CN solvent. Although the XeF(3)(-) anion has been observed in the gas phase, attempts to prepare the Cs(+) and N(CH(3))(4)(+) salts of XeF(3)(-) have been unsuccessful, and are attributed to the low fluoride ion affinity of XeF(2) and fluoride ion solvation in…
New anionic cobalt complexes using highly hindered bis-amides with varying donor abilities as ligands.
2007
Four potential tetradentate ligands of formulae 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)ethane (H(4)L(1), 1), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)propane (H(4)L(2), 2), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)benzene (H(4)L(3), 3) and 1,8-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)naphthalene (H(4)L(4), 4) have been prepared and the crystal structures of three of them (1, 3 and 4) determined by single crystal X-ray diffraction. The investigation of their complexing ability toward Co(II) afforded the compounds of formulae [Co(III)(L(3))Na(I)(H(2)O)(2)] (5), [Co(III)(L(n))Li(I)(H(2)O)2] with n = 1 (6), 2 (7) and 3 (8) and [Co(II)(L(4))Li(I)(2)] (9). Complexes 5-8 are squa…
The different redox-activity of dianthrylbenzene and dianthrylbiphenyl
1989
Abstract The reduction of dianthrylbenzene and dianthrylbiphenyl to stable tetraanion salts is described by NMR spectroscopy and cyclic voltammetry. The significantly different Coulomb interactions between the anthracene units are compared with those in dianthrylalkanes.
New pregnane and phenolic glycosides from Solenostemma argel.
2016
Abstract From the aerial parts, pericarps and roots of Solenostemma argel, three new pregnane glycosides (1–3) with two known ones and a new phenolic glycoside (4) have been isolated. Their structures were established by extensive 1D – and 2D NMR and mass spectroscopic analysis. The cytotoxicity of all compounds was evaluated against two human tumor cell lines (SW 480, MCF-7), but none of them was active in the concentration range 0.9–59.0 μM. Compounds 2 and the known argeloside F at non toxic concentrations for the PBMCs (27.3 μM and 27.6 μM, respectively) significantly decreased the Il-1β production by LPS-stimulated PBMCs. All isolated compounds showed a significant antioxidant potentia…
Synthesis and characterization of complexes of trialkyl- and triarylphosphine gold(I) with thiolated purines and pyrimidines. A class of bifunctional…
1991
Abstract New complexes of the type R 3 PAuL or (R 3 PAu) 2 (μ-L) where R=ethyl or phenyl and L=6-thioguanine, 2, 6- dithioxanthine, 2, 4-dithiouracil and/or dithioerythritol have been prepared. These complexes have been identified by using elemental analysis, 1 H, 13 C and 31 P NMR spectroscopy. The structures have been proposed based on these spectroscopic studies. Sulfur appears to be the binding site in disubstituted complexes of 2, 4-dithiouracil and 1, 4-dithioerythritol, while the phosphine gold( I ) moieties appear to be S and N bonded in 2, 6-dithioxanthine and 6-thioguanine. The potential use of these complexes as antitumor drugs is discussed.
Exploring the Reactivity and Biological Effects of Heteroleptic N-Heterocyclic Carbene Gold(I)- Alkynyl Complexes
2020
With the aim to explore the effects of different organometallic ligands on the reactivity and biological properties of a series of twelve heteroleptic AuI complexes, of general formula [Au(NHC)(alkynyl)] (NHC = benzimidazolylidene or 1,3-dihydroimidazolylidene) were synthesized and characterized by 1H and 13C NMR and elemental analysis, and in some cases also by X-ray diffraction. The compounds were all stable in H2O/DMSO as established by NMR spectroscopy, while they could react with model thiols (EtSH) in the presence of water to undergo ligand-substitution reactions. 1H NMR experiments showed that dissociation of the more labile alkynyl ligand was possible for all compounds, while in the…
Monoterpene derivatives from the flowers of Ferulago campestris, (Apiaceae).
2013
Ferulago campestris (Besser) Grec., (Ferula galbanifera (Mill) Kock. = F. campestris), finocchiazzo, is an annual or perennial herb of the Mediterranean area. In this paper the phytochemical studies of the CH2Cl2 and MeOH extracts of the flowers are described. Several ferulol derivatives and a new 10-hydroxy-verbenone ester (7) were isolated. The structure of the new compound was established by extensive NMR analysis, including HMBC and HSQC pulse sequences.
A study of dimethyltin(IV)-L-cysteinate in aqueous solution
1988
The in vivo activity of some R2Sn-L-cysteinate complexes (R = Me, Et, n-Bu) against murine P-388 leukaemia has been tested. Only the Et2Sn(IV) complex showed a marginal positive effect. Trigonal bipyramidal tin environments with two carbon (R) atoms and the sulfur atom in the equatorial plane and oxygen (carboxylate) and nitrogen (NH2) in apical positions have been proposed for the solid compexes (R = Me, Et, n-Bu, Ph) on the basis of experimental Mossbauer parameters and infrared (IR) data. Aqueous solutions of the Me2SnL-cysteinate have been studied by IR, 1H NMR and 119Sn Mossbauer spectroscopy (in frozen solution) at different pH values to identify the Me2Sn(IV) species present. At pH >…