Search results for "Proton NMR"
showing 10 items of 324 documents
Nanoassemblies Based on Supramolecular Complexes of Nonionic Amphiphilic Cyclodextrin and Sorafenib as Effective Weapons to Kill Human HCC Cells
2015
Sorafenib (Sor), an effective chemiotherapeutic drug utilized against hepatocellular carcinoma (HOC), robustly interacts with nonionic amphiphilic cyclodextrin (aCD, SC6OH), forming, in aqueous solution, supramolecular complexes that behave as building blocks of highly water-dispersible colloidal nanoassemblies. SC6OH/Sor complex has been characterized by complementary spectroscopic techniques, such as UV-vis, steady-state fluorescence and anisotropy, resonance light scattering and H-1 NMR. The spectroscopic evidences and experiments carried out in the presence of an adamantane derivative, which competes with drug for CD cavity, agree with the entrapment of Sor in aCD, pointing out the role…
2H NMR Time Domain Analysis of Ultraslow Reorientations in Supercooled Liquids
1998
A method for evaluating 2H NMR stimulated echo experiments in the time domain is presented. It exhibits a high sensitivity to molecular reorientation mechanisms for small angles. Reorientations with jump angles below 25degrees can be resolved with a precision of approximately 1degrees so that, e.g., rotational diffusion and finite jump angle mechanisms become distinguishable. The method, applicable to isotropic reorientation models, is thought to extend the domain of 2D exchange spectroscopy where the best resolution is obtained in the large angle range of anisotropic reorientational mechanisms. Application to reorientation in the supercooled melt of ortho-terphenyl is presented. These data…
Assignment of1H and13C NMR data for (−)-methyl thyrsiflorin A and some scopadulan precursors
2001
The 1H and 13C NMR spectral analysis of synthetic (−)-methylthyrsiflorin A and 10 scopadulan precursors is reported. Resonance assignments were based on one- and two-dimensional NMR techniques, which included 1H, 13C, DEPT and HMQC and also 1D NOE difference spectroscopy. Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis, characterization and thermal degradation of 8-hydroxyquinoline–guanidine–formaldehyde terpolymer
2007
Abstract Terpolymer (8-HQGF) has been synthesized using the monomers 8-hydroxyquinoline, guanidine, formaldehyde in 1:1:2 molar proportions. The structure of 8-HQGF terpolymer has been elucidated on the basis of elemental analysis and various physicochemical techniques, i.e. UV–Visible, FTIR–ATR and 1 H NMR spectroscopy. Detailed thermal degradation study of the new terpolymer has been carried out to ascertain its thermal stability. Thermal degradation curve is discussed which shows two decomposition steps (265–475 °C and 540–715 °C). Sharp–Wentworth and Freeman–Carroll methods have been used to calculate activation energies and thermal stability. The activation energy ( E a ) calculated by…
Mono-, bi- and polynuclear complexes of dimethyldiphenylsilane, diphenylether and biphenyl with Cr, Co and Ru. Synthesis and 1H, 13C, 17O and 29Si NM…
1995
Abstract Mono- and bimetallic transition metal carbonyls of dimethyldiphenylsilane, Ph 2 Si(CH 3 ) 2 (L1), diphenylether, Ph 2 O (L2) and biphenyl, Ph 2 (L3): Ph 2 Si(CH 3 ) 2 Cr(CO) 3 ( 1 ), Ph 2 Si(CH 3 ) 2 [Cr(CO) 3 ] 2 ( 2 ), Ph 2 Si(CH 3 ) 2 Co 4 (CO) 9 ( 3 ), Ph 2 Si(CH 3 ) 2 [Co 4 (CO) 9 ] 2 ( 4 ), Ph 2 Si(CH 3 ) 2 Cr(CO) 3 Co 4 (CO) 9 ( 5 ), Ph 2 OCr(CO) 3 ( 6 ), Ph 2 OCo 4 (CO) 9 ( 7 ), Ph 2 ORu 6 C(CO) 14 ( 8 ), Ph 2 OCr(CO) 3 Co 4 (CO) 9 ( 9 ) and Ph 2 Ru 6 C(CO) 14 ( 10 ) have been prepared and characterized by means of 1 H, 13 C, 17 O and 29 Si NMR spectroscopy. The same order of the shielding effects induced by the transition metal (Co 1 H NMR chemical shifts of the η 6 -coord…
Metalloporphyrins with metalmetal σ-bonds. Synthesis, spectroscopic characterization, and electrochemistry of (P)MRe(CO)5 where P is the dianion of …
1991
Abstract The synthesis, physicochemical properties, and electrochemistry of a new series of metal metal σ-bonded metalloporphyrins are reported. The investigated compounds are represented as (P)MRe(CO)5 where P is the dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP) and M = Al, Ga, In, or Tl. These compounds provide the first examples of Al and Ga metalloporphyrins with covalent metalmetal bonds as well as give the first series of compounds in which the same metalate anion is covalently bonded to four different group 13 metalloporphyrins. Each synthesized complex was characterized by 1H NMR, IR, and UV-visible spectroscopy as well as by electrochemistry. Graham Δσ and Δπ …
Chiroptical Phenomena in Reverse Micelles: The Case of (1R,2S)-Dodecyl (2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium Bromide (DMEB)
2014
(1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) aggregates dispersed in carbon tetrachloride have been investigated by Fourier transform infrared (FT-IR), vibrational circular dichroism (VCD) and 1H nuclear magnetic resonance (NMR) spectroscopy at various surfactant concentration and water-to-surfactant molar ratio. Experimental data indicate that, even at the lowest investigated concentration and in absence of added water, DMEB molecules associate in supramolecular assemblies. At higher DMEB concentration the aggregates can confine water molecules, making it plausible to think that DMEB form reverse micelles and that water molecules are quite uniformly dist…
X-ray Crystal Structure of Woodinine and Conformational Analysis by Semiempirical and 1H-NMR Methods
1997
The mol. structure of (-)-woodinine (I), a carboline-based alkaloid with antibacterial and antimycobacterial activities, was investigated by X-ray crystallog., NMR, and semiempirical quantum chem. methods. The X-ray crystal structure of I showed the indole ring in the expected planar conformation, the pyrrolidine ring in an envelope conformation, and a weak intramol. hydrogen bond between the pyrrolidine nitrogen and the proton of the indole nitrogen. NMR expts. indicated that this hydrogen bond is not present in soln. and that further differences exist between the crystal and the soln. structures of I. By semiempirical quantum chem. methods, different local energy min. conformations of I, …
1,3-Alternate calix[4]arenes, selectively functionalized by amino groups
2004
General strategies are described to synthesize calix[4]arenes which are fixed in the 1,3-alternate conformation and substituted selectively by amino groups. These derivatives are useful starting materials for the attachment of various groups via amide bonds, as demonstrated by several examples, but may be converted also to ureas, imides or azomethines. Four amino groups may be attached to the narrow rim via(several) methylene groups as spacer by O-alkylation with omega-bromophthalimides or omega-bromonitriles. From the resulting tetraethers the amino functions are obtained by cleavage with hydrazine or by hydrolysis, allowing a selective functionalisation of both sides of the molecule (phen…
Spin lattice relaxation rates of tunnelling CD3 groups
1991
The spin lattice relaxation rates of deuterated methyl groups are calculated for threefold and sixfold potentials. It is shown that it should be possible to determine the symmetry of the potential hindering the methyl groups from deuteron spin lattice relaxation experiments. The temperature dependence of the spin lattice relaxation rates is discussed using a simple model. The similarities and the differences between proton NMR and deuteron NMR are pointed out. The main difference is thatEa↔Eb transitions are forbidden by spin selection rules in case of CH3, but not for CD3. Therefore, and due to the fact that the quadrupolar interaction is a single particle interaction, deuteron NMR allows …