Nuclear magnetic resonance study of complexes formed between conjugated Schiff bases and carboxylic acids

1994 ◽  
Vol 72 (11) ◽  
pp. 2220-2224
Author(s):  
H. Le-Thanh ◽  
D. Vocelle
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Carboxylic Acids ◽  
Nmr Spectra ◽  
Polar Solvent ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Natural Pigments ◽  
H Nmr ◽  
Rapid Proton ◽  
Tert Butylamine

The NMR spectra of the proton located in a N+---H---−O bond formed in the reaction of a conjugated Schiff base (SB) with a carboxylic acid (HA) in a non-polar solvent indicate that this proton is rapidly exchanging with other protons present in the system. For this study, two SB were used: all-trans-retinylidene tert-butylamine (RBA) and trans, tran-2,4-heptadienylidene tert-butylamine (HBA), and five carboxylic acids having pKa's between 0.66 and 4.87.1H NMR spectra were taken at 293 and 233 K in CDCl3 of systems of SB:HA using different ratios of acid to SB. Results indicate that the rapid proton exchanges are temperature and concentration dependent. Finally, the results are related to the natural pigments rhodopsin and bacteriorhodopsin.

A 19F nuclear magnetic resonance study of the conjugate Brönsted-Lewis superacid HSO3F-SbF5. Part 1

1999 ◽  
Vol 77 (11) ◽  
pp. 1869-1886 ◽  
Author(s):  
Dingliang Zhang ◽  
Markus Heubes ◽  
Gerhard Hägele ◽  
Friedhelm Aubke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Formation Reaction ◽  
H Nmr ◽  
Acid Conjugate ◽  
Nmr Methods ◽  
Cis And Trans

The Brönsted-Lewis superacid HSO3F-SbF5 or "magic acid" is re-investigated by modern 19F NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6]-, [SbF5(SO3F)]-, cis- and trans-[SbF4(SO3F)2]-, and mer-[SbF3(SO3F)3]- gradually decreases. Except for [Sb2F11]-, which is present in very small concentrations only, the formation of oligomers involves exclusively μ-fluorosulfato bridges. In addition to donor (SO3F)- and acceptor (SbF5) complex formation to give [SbF5(SO3F)]- and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O]+, which has previously been identified by 1H NMR and structurally characterized as [H3O][Sb2F11] by us.Key words: magic acid, conjugate superacid, fluorosulfuric acid, 19F NMR spectra.

Antimony-121 nuclear magnetic resonance study of hexahaloantimonate anions

1981 ◽  
Vol 59 (20) ◽  
pp. 2940-2949 ◽  
Author(s):  
R. Garth Kidd ◽  
H. Garth Spinney
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectra ◽  
Central Atom ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Acetonitrile Solution ◽  
Trans Isomers ◽  
Magnetic Resonance Study ◽  
Chlorine Substitution ◽  
Nuclear Shielding

The seven hexahaloantimonate anions in the series [SbClnBr6−n]− have been prepared and their antimony-121 nmr spectra show that for [SbCl4Br2]−, [SbCl3Br3]−, and [SbCl2Br4]−, only the cis isomers are present in acetonitrile solution. The pairwise additivity model for central atom shielding has been used for configuration assignments. Models relevant to the higher incidence of cis over trans isomers are discussed. The nuclear shielding of 121Sb is the most sensitive to halogen substitution of all the elements whose halide chemical shifts have been studied. Antimony shieldings exhibit normal halogen dependence, with bromine substitution causing upfield shifts relative to chlorine substitution.

A 19F nuclear magnetic resonance study of the conjugate Brønsted–Lewis superacid HSO3F–SbF5. Part II.

2002 ◽  
Vol 80 (9) ◽  
pp. 1265-1277 ◽  
Author(s):  
Jobst Kühn-Velten ◽  
Matthias Bodenbinder ◽  
Raimund Bröchler ◽  
Gerhard Hägele ◽  
Friedhelm Aubke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Acid System ◽  
Exchange Reactions ◽  
Magnetic Resonance Study ◽  
Dilute Solutions ◽  
H Nmr ◽  
Anionic Species ◽  
High Concentrations ◽  
Initial Process

Solutions of SbF5 in HSO3F with xSbF5 = 0.012 to 0.405 are studied by 500 MHz 1H NMR (299 K) and 471 MHz 19F NMR (213–250 K), using NMR tubes fitted with fluoropolymer lining. The initial process during dissolution is the fast solvolysis of monomeric SbF5 in HSO3F according to SbF5 + nHSO3F [Formula: see text] SbF5 – n(SO3F)n + nHF (n = 1, 2). All HF formed during solvolysis will no longer be removed by reaction with glass, but will remain in the superacid system. Besides participation in the fast formation of various fluoro-fluorosulfato anions [SbF6 – n(SO3F)n]– (n = 0, 1, 2) and acidium ions [H2X]+(solv.) (X= F, SO3F), HF is involved in slow-exchange reactions of the type [SbF6 – n(SO3F)n]–(solv.) + HF [Formula: see text] [SbF7 – n(SO3F)n– 1]–(solv.) + HSO3F (n = 1, 2) detected because of a delay of 3 months between sample preparation and measurements and confirmed by repeating theses measurements after a further 3 months. There are three notable differences to our earlier study, affecting concentrations of the fluoro-fluorosulfato antimonate anions observed: (i) in dilute solutions [SbF6]– is formed in high concentrations (34.7–76.1%), with [Sb2F11]– now clearly detected at intermediate to high SbF5 concentrations (up to 5.8%); (ii) bis-fluorosulfato anions (cis-, trans-[SbF4(SO3F)2]–) are found in much lower concentrations only, which decrease further with time, while tris-fluorosulfato anions ([SbF3(SO3F)3]–) are now no longer observed; (iii) these reduced concentrations of poly-fluorosulfato anions in dilute solutions are responsible for the formation of fewer µ-SO3F-oligomers at lower concentrations, when more SbF5 is added. As a consequence, the HSO3F–SbF5 magic acid system is now less complex than found previously and only seven anionic species are clearly observed. Key words: superacids, antimony(V) fluoroanions, 1H NMR, 19F NMR, solvolysis.

A nuclear magnetic resonance study of Al–Mn quasicrystals and related materials

1987 ◽  
Vol 2 (4) ◽  
pp. 431-435 ◽  
Author(s):  
Keith R. Carduner ◽  
B. H. Suits ◽  
J. A. DiVerdi ◽  
Michael D. Murphy ◽  
David White
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Melt Spinning ◽  
Nmr Spectra ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Broad Distribution ◽  
Quadrupole Field ◽  
Melt Spinning Technique ◽  
Nuclear Magnetic

Nuclear magnetic resonance (NMR) results are presented for several aluminum alloy samples prepared using the melt-spinning technique including orthorhombic Al6Mn, Al–Mn quasicrystals both with and without doping with Si and Ru, and a T-phase alloy of Al and Pt. With the exception of the orthorhombic material, all of the NMR spectra show a broad distribution of sites. No features unique to the quasicrystal phase are observed. For the orthorhombic material the quadrupole field parameters are found to be ∥VQ∥ − 1.0±0.1 MHz and η = 0.4±0.1.

Nuclear magnetic resonance study of the interaction of neodymium(III) with amino acids and carboxylic acids. Aqueous shift reagent

1973 ◽  
Vol 95 (9) ◽  
pp. 3011-3014 ◽  
Author(s):  
A. Dean. Sherry ◽  
Calvin. Yoshida ◽  
Edward R. Birnbaum ◽  
Dennis W. Darnall
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Carboxylic Acids ◽  
Nuclear Magnetic Resonance Study ◽  
Shift Reagent ◽  
Magnetic Resonance Study ◽  
Nuclear Magnetic

15N and 77Se Nuclear Magnetic Resonance Study of Selenium Diimides and Aminoselenanes

1993 ◽  
Vol 48 (10) ◽  
pp. 1307-1314 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Berthold Distler ◽  
Silke Gerstmann ◽  
Max Herberhold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Nmr Spectra ◽  
Decomposition Product ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Magnetic Resonance Study ◽  
Nmr Data ◽  
Cp Mas Nmr ◽  
Membered Heterocycle

Selenium diimides R(NSeN)R [R = tBu (1a), tOct (1b)], the eight-membered heterocycle tBuN(SeSeSe)2NtBu (2) and the aminoselenanes of the type [R(Cl3Si)N]2Se (4a,b) and [(Me3Si)2N]2Se (5) were studied by multinuclear NMR with emphasis on 15N NMR for detection of coupling constants J(77Se15N). The selenium diimides possess the largest values of 1J(77Se15N) observed so far (1a: 158.4 and 163.5 Hz; 1 b: 158.6 and 162.8 Hz). Compound 1 b was found to be much more stable than 1a, the heterocycle 2 being the major decomposition product of 1a. The selenium diimides (1a,b) react readily with hexachlorodisilane to give the bis[alkyl(trichlorosilyl)amino]selenanes 4a,b. The solid state 13C, 15N, 29Si and 77Se CP/MAS NMR spectra of bis[bis(trimethylsilyl)amino]selenane (5) gave results in accord with the known crystal structure, and there is agreement with the solution state NMR data

α-N,N-Dimethylaminoethylferrocene. A nuclear magnetic resonance study relating to stereoselective metalation

1986 ◽  
Vol 64 (4) ◽  
pp. 667-669 ◽  
Author(s):  
Ian R. Butler ◽  
William R. Cullen ◽  
F. Geoffrey Herring ◽  
N. R. Jagannathan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spatial Correlation ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
H Nmr ◽  
Nmr Study ◽  
Nuclear Magnetic

A 1H nmr study of Fe(C5H4CHMeNMe2-η)(C5H4PPh2-η), 2, using the nOe difference experiment, shows a spatial correlation between the —NMe2 group and the site of stereoselective lithiation.

Synthesis and nuclear magnetic resonance study of the compounds (2-X-1,3-dithiane) (X = H, Me, SiMe3, GeMe3, SnMe3, PbMe3) and their tetracarbonyliron complexes

1978 ◽  
Vol 56 (11) ◽  
pp. 1538-1544 ◽  
Author(s):  
David J. Cane ◽  
William A. G. Graham ◽  
Liviu Vancea
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Energy Barrier ◽  
Nmr Spectra ◽  
Nuclear Magnetic Resonance Study ◽  
Carbonyl Groups ◽  
Magnetic Resonance Study ◽  
Ring Inversion ◽  
C Nmr

A series of (1,3-dithiane)Fe(CO)4 complexes, (2-X-1,3-dithiane)Fe(CO)4, X = H, Me, SiMe3, GeMe3, SnMe3, PbMe3, has been prepared and characterized, and both the complexes and the free ligands studied by 1H and 13C nmr spectroscopy. The energy barrier to ring inversion in (1,3-dithiane)Fe(CO)4, ΔG298†, is 14.7 ± 0.2 kcal mol−1, some 4.4 kcal mol−1 higher than in free 1,3-dithiane.13C nmr spectra showed that within the Fe(CO)4 moiety, rapid averaging of carbonyl groups occurs down to at least −80 °C.

Halogen and pseudohalogen substitution of some adamantanoid chalcogenate clusters [(μ-EPh)6(MEPh)4]2− using methylmercury and triphenyltin derivatives. A multinuclear nuclear magnetic resonance study

1988 ◽  
Vol 66 (9) ◽  
pp. 2443-2451 ◽  
Author(s):  
Philip A. W. Dean ◽  
Jagadese J. Vittal
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Tetraalkylammonium Salts ◽  
Magnetic Resonance Study ◽  
Nmr Spectrum ◽  
Alternative Synthesis ◽  
H Nmr ◽  
Nmr Characterization

Multinuclear nmr (1H, 77Se, 111/113Cd, 119Sn, 199Hg, as appropriate) has been used to study Y−−EPh− exchange in Me2CO or MeCN between RnM′Y (RnM′ = Ph3Sn or MeHg; Y = Cl, Br, I, NCO, or NCS) and the adamantane-like anions [(μ-EPh)6(MEPh)4]2− (E = S, M = Zn, Cd, or Co; E = Se, M = Zn or Cd), as their tetraalkylammonium salts. Quantitative terminal substitution of the clusters occurs in most cases, giving [(μ-EPh)6(MEPh)4 − x(MY)x]2−(x = 1–4). However, reaction is incomplete for M = Cd, E = S or Se, RnM′Y = Ph3SnNCO or Ph3SnNCS and for M = Zn or Co, E = S, RnM′Y = MeHgI. Differences in the extents of reaction for Ph3SnY and MeHgY are consistent with the position of equilibrium in MeHgY:Ph3SnEPh mixtures.Group interchange provides a convenient alternative synthesis of the known halogen-substituted clusters [(μ-EPh)6(MY)4]2−(M = Zn or Cd, Y = Cl, Br, or I; M = Co, Y = Cl), and the first syntheses of [(μ-SPh)6(CoY)4]2− (Y = Br or I) and various pseudohalogen-substituted adamantanoid anions. The nuclei used for full direct nmr characterization of the new clusters in solution were: 77Se and 113Cd for [(μ-SePh)6(CdSePh)4 − x(CdY)x]2− (x = 1–4; Y = NCO or NCS); 77Se for [(μ-SePh)6(ZnSePh)4 − x(ZnY)x]2− (x = 1–4, Y = NCO or NCS); 113Cd for [(μ-SPh)6(CdSPh)4 − x(CdY)x]2−(x = 1–4; Y = NCO or NCS); 1H for [(μ-SPh)6(CoY)4]2− (Y = Br, I, NCO, or NCS). The first solution 1H nmr spectrum of [(μ-SPh)6(CoCl)4]2− is also reported.

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