bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of the H/D isotope shifts of the 13C nuclear shielding to the nitrogen lone pair delocalization in anilines and acetanilides
Authors: Morales‐Ríos Martha S. , Joseph‐Nathan Pedro
Published: May 2005

Two‐ and three‐bond deuterium isotope shifts (2Δ and 3Δ) of the 13C nuclear shielding were measured for a series of para‐substituted anilines and acetanilides, in which the amide NH or the amine NH2 hydrogens were partially exchanged with deuterium. The results show that when strong electron‐donating groups are present at the para position in acetanilides, the 2Δ(C‐1) isotope shifts are smaller than the 3Δ(C‐2,6) isotope shifts. Empirical correlations that relate 2Δ isotope shifts with 1H(NH), 13C(C‐ipso), 15N(NH2 or NH), 17O(CO) NMR chemical shifts and with 3Δ isotope shifts are presented. The results are interpreted in each series as depending on the characteristic nitrogen lone pair delocalization.
Selenium—selenium bond order in diselenides. 77Se–77Se and 77Se–13C coupling constants and 77Se chemical shifts of symmetrical and unsymmetrical diselenides
Authors: Gombler Willy
Published: May 2005

77Se–77Se spin‐spin coupling constants of unsymmetrically and, for the first time, of symmetrically substituted diselenides have been measured for CF3SeSeCH3, CF3SeSeCF3, CF3SeSeCF2Cl and CF2ClSeSeCF2Cl. A correlation of the 1J(SeSe) values with the average 77Se shielding is found for perhalomethyl diselenides and organyl diselenides. 77Se–13C coupling constants are also reported for the perhalomethyl diselenides. The coupling constants are much larger than in organyl diselenides. NMR data for the thioselenides CF3SeSR (R = CF3, CF2Cl, CFCl2, CCl3) are reported for comparison. It can be concluded that π‐type interactions occur in the SeSe or SeS bonds of diselenides and thioselenides, respectively, containing perhalomethyl groups.
Long‐range heteronuclear correlation 2D NMR by MLEV‐16 isotropic mixing
Authors: Morris Gareth A. , Gibbs Andrew
Published: May 2005

Coherence transfer by MLEV‐16 isotropic mixing is shown to be an efficient way of obtaining phase‐sensitive heteronuclear chemical shift correlation 2D spectra. Both long‐ and short‐range correlations are possible by appropriate choice of mixing time. At long mixing times, the contribution of coherence transfer pathways through multiple couplings extends the range of correlation. Long mixing time experiments may therefore be useful for structure determination in total unknowns. Results are presented for a 13C‐detected isotropic mixing experiment on menthol.
Complete 1H and 13C assignment of some cubane derivatives by 2D NMR spectroscopy
Authors: Axenrod T. , Liang B. , Bashir‐Hashemi A. , Dave P. R. , Reddy D. S.
Published: May 2005

The 13C and 1H chemical shift values of 31 cubanes ranging from mono‐ to hexa‐substituted derivatives were recorded in CDCl3 solution and the spectra were fully assigned using, where necessary, 2D 13C–H shift correlated spectra optimized for either one‐bond or long‐range 13C–H couplings. The one‐bond 13C–H coupling constants for the cubyl carbon resonances were also measured and tabulated.
Isotope effects on 31P nuclear shielding in thiophosphites
Authors: Démarcq Michel C. , Le Gleut Louis , Van Hemelryck Bruno G.
Published: May 2005

The 34S isotope effect on the chemical shift of PIII nuclei in P(SR)3 esters [R = Et, (C12H25)n, Ph] is close to 20.6 ppb per PIII34S bond, i.e. 3–4 times larger than for thiolo sulphur atoms in S = P(SR)3 or O = P(SR)3. A similar behaviour is noted for the P(S)3 sites in P4S9 and P4S3 and for the downfield triplet of P4S8, which, accordingly, is assigned to the tri‐coordinate P atoms of this sulphide. 13C isotope effects are also reported for trialkyl(aryl) phosphorotrithioites and S,S,S‐phosphorotrithioates.
Solid‐state (CP‐MAS) 29Si‐, 119Sn and 207Pb nuclear magnetic resonance study of bis(pentamethylcyclopentadienyl)‐silicon, ‐tin and ‐lead
Authors: Wrackmeyer Bernd , Sebald Angelika , Merwin Lawrence H.
Published: May 2005

Solid‐state CP‐MAS 29Si‐, 119Sn‐ and 207Pb NMR spectra of bis(pentamethylcyclopentadienyl)‐silicon (1) ‐tin (2) and ‐lead (3) were measured. The spectra reflect the gross structural features, known from x‐ray analyses for 1–3. In 1a, which has a parallel arrangement of the Me5C5 rings, the 29Si nuclear shielding is found to be 20.2 ppm higher than that of the bent structure in 1b. The assignment is supported by the relative intensities of the 29Si resonances and by the analyses of the spinning sideband patterns. The δ29Si value of 1 in solution is close to that of 1b, suggesting that the bent structure is preferred in solution. The comparison of the solution‐ and solid‐state δ values shows that the η5‐bonding of the cyclopentadienyl rings is retained in solution. Attempts to analyse the spinning sideband pattern of 2 by the usual methods failed, which may be explained by the presence of molecular reorientation in the solid state which occurs at room temperature at a rate affecting the 119Sn shielding tensor.
Spectral reassignment and structure elucidation of scopolamine free base through two‐dimensional NMR techniques
Authors: Sarazin Catherine , Goethals Gérard , Séguin Jean‐Paul , Barbotin Jean‐Noël
Published: May 2005

The combination of 1D and 2D NMR techniques, especially the long‐range heteronuclear chemical shift correlation experiment, has permitted the reassignment of some carbons and protons of scopolamine free base in CDCl3 solution and the differentiation of each atom of the piperidine ring. In contrast to literature data, and to the protonated state conformation, these studies showed that the methyl group is equatorially disposed relative to the piperidine ring. NMR and IR spectroscopic results demonstrated that the OH group is connected by a hydrogen bond to the phenyl ring at a low concentration, but an intermolecular hydrogen bond is formed at high concentration.
13C NMR chemical shift assignments for some n‐butylthiomethylene ketones
Authors: Guerrero Angel , Parrilla Alfredo , Sanchez Francisco J.
Published: May 2005

The 13C NMR spectra of a series of 2‐(n‐butylthiomethylene) cycloalkanones and 2‐(n‐butylthiomethylene) 1‐decalones were recorded and unequivocally assigned by the study of correlation signals in DQCOSY and HETCOR experiments. The effect caused by the introduction of the n‐butylthiomethylene group in comparison with the corresponding parent compounds is discussed.
1H and 13C NMR assignments of the antitumor macrolide bryostatin 1
Authors: Schaufelberger Daniel E. , Chmurny Gwendolyn N. , Koleck Mary P.
Published: May 2005

During a large‐scale isolation of bryostatin 1, NMR measurements indicated that parts of the published 13C and 1H NMR assignments had to be revised. These reassignments were based on extensive homonuclear and heteronuclear one‐ and two‐dimensional NMR techniques performed at 500 MHz. These independently obtained assignments are also in good agreement with the revised assignments and structure of bryostatin 3.
Nitrogen‐15 NMR spectroscopy: Nitrogen‐15 chemical shifts of 1,2‐diaminobenzenes and 1,8‐diaminonaphthalenes
Authors: Sibi Mukund P.
Published: May 2005

Nitrogen‐15 chemical shifts of 1,2‐diaminobenzenes, 1,8‐diaminonaphthalenes and their monoprotonated species are reported.
Nitrogen‐15 NMR spectroscopy: Nitrogen‐15 chemical shifts of alkylthioureas
Authors: Sibi Mukund P.
Published: May 2005

Nitrogen‐15 chemical shifts of alkylthioureas in dimethylsulphoxide and pyridine are reported.
NMR examination of tricyclo[4.2.0.01,3]octane
Authors: Smith William B. , Brinker Udo H.
Published: May 2005

The structure of the strained tricyclic hydrocarbon tricyclo[4.2.0.01,3]octane was determined by a combination of 1D and 2D NMR involving both proton and carbon signals. The stereochemistry of the molecule was determined by NOE difference spectroscopy. The assigned structure corresponds to the thermodynamically more stable trans form as ascertained by molecular mechanics calculations.
EPR spectra in γ‐irradiated PPN+HFeW(CO)9− crystals
Authors: Hynes Rosemary C. , Springs Jerry J. , Preston Keith F. , Williams Antony J.
Published: May 2005

Single crystals of PPN+HFeW(CO)9− prepared from THF · W(CO)5 and PPN+HFe(CO)4− exhibit weak single‐line EPR spectra corresponding to the presence of two paramagnetic impurities. One of the spectra increases in intensity by an order of magnitude on 60Co γ‐irradiation. The g2 matrices for both species in an orthogonal crystal‐axis system were assembled from measurements of g values made at 77 K on crystallographically oriented samples. The intense spectrum has principal g values of 2.0064, 2.0468 and 2.1320 and principal directions of g which lie close to bonds emanating from the Fe nucleus of the undamaged anion. Consideration of the principal g values and directions for this species leads to an assignment to a FeW(CO)9− radical in which the unpaired electron is principally located in a Fe 3d orbital directed along the FeH bond of the host anion. The other signal has principal g values (2.0229, 2.0425, 2.0950) close to those established for the singly bridged isomer of Fe2(CO)8−, but their directions do not correlate well with bond directions within the host anion. It is concluded that small amounts of the persistent Fe2(CO)8− radical generated in the preparative procedures substitute for the host anion in the crystals of PPN+HFeW(CO)9−.
1H and 13C NMR analyses of amiodarone, desethylamiodarone and desoxoamiodarone
Authors: Ribeiro Anthony A. , Jendrasiak Gordon L.
Published: May 2005

The 1H and 13C NMR spectra of amiodarone, a potent cardiac antiarrhythmic agent, desethylamiodarone, the main metabolite of amiodarone and desoxoamiodarone, a less toxic form of amiodarone, were assigned using a combination of NMR techniques. Methods applied include 1H‐1H COSY, homonuclear Hartmann–Hahn relayed spectroscopy (HOHAHA), broadband decoupled 1H–13C chemical shift correlation, long‐range 1H–13C chemical shift correlation and selective INEPT. This combination of NMR experiments has completed a molecular walk along the covalent framework of the cardiac drug molecules, and removed ambiguities in their 1H and 13C NMR assignments.
1H and 13C NMR studies of 1,8‐bis(dimethylamino)naphthalene salts in acetonitrile‐d3
Authors: Brycki Bogumil , Brzeziński Bogumil , Grech Eugeniusz , Malarski Zbigniew , Sobczyk Lucjan
Published: May 2005

1H and 13C NMR spectra were studied for a number of 1,8‐bis(dimethylamino)naphthalene (DMAN) salts in acetonitrile‐d3. In the case of strong acids no counter anion effect was observed on the protonated DMAN molecules. A splitting of the 1H signal of the CH3 groups was found which was caused by coupling with the bridge NHN+ proton. It was confirmed that the salt with pentachlorophenol (PCP) undergoes a transformation to a nearly equimolar solution of free DMAN, protonated DMAN and the homoconjugated anion of PCP. The formation of the NHN+ bridge with an equally shared proton between the two nitrogen atoms leads to a change in the charge distribution in the naphthalene ring which is analogous to, but much weaker than, that found on protonation of aniline.
Natural abundance nitrogen‐15 CP‐MAS NMR studies of copper(I) complexes
Authors: Kitagawa Susumu , Munakata Megumu , Deguchi Kenzou , Fujito Teruaki
Published: May 2005

Natural abundance 15N CP‐MAS NMR spectra of copper(I) complexes and their ligands, [Cu(biL)2]PF6 [biL = 1,10‐phenanthroline (phen) and 2,9‐dimethyl‐1,10‐phenanthroline (2,9‐Me2phen)], were measured. Coordination shifts of −45 and −44 (average) ppm were obtained for phen and 2,9‐Me2phen, respectively, which are attributed to the stabilization of the nitrogen lone‐pair orbital and the involvement of the metal d‐orbital via π‐back‐bonding.
Assignment of proton NMR resonances and conformational analysis of [Lys8]‐vasopressin homologues
Authors: Zieger G. , Andreae F. , Sterk H.
Published: May 2005

The assignment of proton NMR signals and the conformational analysis of N‐(Gly)–[Lys8]–vasopressin and N‐(GlyGlyGly)[Lys8]‐vasopressin in dimethyl sulfoxide solution by means of one‐ and two‐dimensional NMR techniques are presented. Dihedral angles obtained from 3J (HNCα‐H) vicinal couplings, intramolecular distances estimated from nuclear Overhauser enhancements (NOEs) and two‐dimensional experiments in the rotating frame (ROESY), as well as temperature dependences of the amide protons, suggest a more or less rigid ring conformation with an inverse γ‐turn for both cyclic peptides.
NMR spectra and stereochemistry of 5,5‐disubstituted‐1,3‐dioxans
Authors: Crabb Trevor A. , Porssa Manuchehr , Elmore Norman F.
Published: May 2005

The positions of conformational equilibria in a variety of 5,5‐disubstituted 1,3‐dioxans have been established by low‐temperature 1H and 13C NMR spectroscopy and by reference to the NMR spectra of anancomeric 2,5,5‐trisubstituted derivatives.
Solution and powder X‐ and Q‐band ESR spectra of the 1,3,5‐ trithia‐2,4, 6‐triazapentalenyl radical
Authors: Chung Y.‐L. , Sandall J. P. B. , Sutcliffe L. H. , Joly H. , Preston K. F. , Johann R. , Wolmershäuser G.
Published: May 2005

From the ESR spectra of the stable 1,3,5‐trithia‐2,4,6‐triazapentalenyl free radical, obtained at two microwave frequencies in both the solution and the solid state, it was shown to be a π radical. From the spectra and their computer simulations were derived an unpaired s‐spin population of 1.7% for the unique nitrogen and 0.1% for the two equivalent nitrogens. The corresponding px‐spin populations were found to be 43.5% and 1.8%, respectively. The unpaired s‐spin population of the two equivalent sulphurs was estimated to be 0.3%.
Proton and carbon‐13 NMR spectra of some 3,4‐fused pyranocoumarins and furocoumarins
Authors: Patra Amarendra , Panda Samir K. , Majumdar K. C. , Khan A. T. , Saha S.
Published: May 2005

Carbon‐13 spectral assignments of five pyrano [3,2‐c] [1] benzopyran‐5 (2H)—ones, five pyrano[2,3‐c][1] benzopyran‐5 (2H)—ones and five 2‐methylfuro[2,3‐c][1] benzopyran‐4‐ones and of 2‐methylfuro [3,2‐c][1]benzopyran‐4‐one and 4‐(2‐chloroallyl)‐3‐hydroxycoumarin were made from mutual correlations, 13C/1H coupling constant measurements and 2D X–H correlation analyses. High‐resolution proton resonance assignments of these compounds are reported.
13C CP‐MAS solid‐state NMR and multinuclear solution state magnetic resonance spectra of some sulphur amides and carboxamides
Authors: Häkkinen Anna‐Maija , Ruostesuo Pirkko A.
Published: May 2005

The 13C NMR chemical shifts in the solution and in the solid state and those of 15N and 17O and the line widths of the 14N and 17O resonance signals in the solution state were determined for carboxamides, aliphatic and aromatic sulphon‐ and sulphin‐amides and a thioamide (thioacetamide).
Complexation of potassium cations by tetraglyme and 18‐crown‐6 as evidenced by 39K NMR spectroscopy
Authors: Grobelny Janusz , Sokól Maria , Jedliński Zbigniew J.
Published: May 2005

39K NMR spectroscopy was used to study a blue potassium solution in tetraglyme containing 18‐crown‐6 and in a solution without the crown ether. Direct proof of the existence of potassium anions and complexed potassium cations in both solutions has been presented.
NMR/NOE elucidation of the stereostructure of cycloadducts of acetonitrile oxide with norbornane/ene‐fused dihydro‐oxazines
Authors: Sohár Pál , Stájer Géza , Szabó Angela E. , Bernáth Gábor
Published: May 2005

Norbornane‐di‐endo‐ and ‐di‐exo‐fused dihydro‐1,3‐oxazines underwent cycloaddition with in situ prepared acetonitrile oxide to yield tetracyclic 1,2,4‐oxadiazolines. Either the CC bond of the double dipolarophiles with the norbornene skeleton was saturated to give isoxazoline regioisomers, or a second molecule of the dipole added to the CN bond, resulting in the formation of a bis‐adduct. The structures of the products were confirmed by 1H and 13C NMR spectroscopy, making use of DNOE experiments.
Improved sensitivity for the 2D analogue of the 3D HOHAHACOSY experiment
Authors: Bircher Hansruedi , Müller Christian , Bigler Peter
Published: May 2005

An improved 2D sequence for the simplification of COSY spectra is described and demonstrated. It is based on the 3D HOHAHACOSY experiment, makes use of shaped selective pulses and takes advantage of simultaneous excitation and correspondingly more efficient data accumulation schemes. The method is particularly suitable for applications in the fields of peptides, carbohydrates and nucleotides.
ENDOR study of the intermolecular interactions of bis(O,O′‐dialkyldithiophosphate)copper(II) with diamagnetic matrices
Authors: Iliev V. I. , Macicek J.
Published: May 2005

Polycrystalline samples of dithiophosphate (dtp) complexes CuII[Cu(R2dtp)2], magnetically diluted in Ni (R2dtp)2, Pd(R2dtp)2 or Pt(R2dtp)2 matrices (R = CH3, C2H5 or i‐C3H7) were studied. ENDOR transitions for the 1H and 31P nuclei belonging to the copper(II) dithiophosphate molecules were recorded for the Cu/Ni(Me2dtp)2, Cu/Ni(Et2dtp)2, Cu/Pd(Et2dtp)2, Cu/Pt(Et2dtp)2 and Cu/Ni(i‐Pr · dtp)2 samples. In the case of Cu/Pd(Me2dtp)2, Cu/Pt(Me2dtp)2, Cu/Pd(i‐Pr · dtp)2 and Cu/Pt(i‐Pr · dtp)2, in addition to the above‐mentioned ENDOR transitions, 1H and 31P transitions were recorded for nuclei which belong to the dithiophosphate molecules of the diamagnetic matrix. It was established that the crystal packing of the molecules of the diamagnetic matrices favours intermolecular interactions. Spin density transfer for the molecules of the diamagnetic matrices was observed only in the case when Cu(R2dtp)2 is included in crystal lattices having only one molecule in the unit cell (Z = 1). The coplanar arrangement (for Z = 1) of the chelate rings from neighbouring paramagnetic and diamagnetic molecules favoured the transfer of the spin density on the 31P nuclei of the latter. The high value of the isotropic hyperfine splitting constant in the 31P nuclei from the diamagnetic molecule is explained by the weak overlapping of orbitals from neighbouring molecules. The intermolecular interactions leading to the occurrence of ENDOR transitions in the 1H nuclei which belong to the molecules of the diamagnetic matrix are also discussed.
Configuration and conformation derived from 1H and 13C NMR spectroscopy of a series of substituted penta‐1,3‐dien‐5‐ols
Authors: Sergeyev N. M. , Chertkov V. A. , Torocheshnikov V. N. , Roznyatovsky V. A. , Panosyan G. A. , Shakhatuni A. G. , Khrimian A.
Published: May 2005

Established NMR criteria from 1H, 13C and 2D J‐resolved 13C NMR spectra, and also 1H{1H} NOE experiments, were used to determine the constitution and configuration in a series of substituted penta‐1,3‐dien‐5‐ols.
Additivity scheme for 13C NMR chemical shifts in triangulanes
Authors: Lukin Kirill A. , Kozhushkov Sergei I. , Zefirov Nikolai S.
Published: May 2005

The 13C NMR spectra of triangulanes, the unique class of hydrocarbons constructed from spiroannulated cyclopropanes, were analysed, and correlations were revealed between their structures and 13C chemical shifts. The procedure for the configurational assignment in triangulanes based on the 13C NMR spectral data is described.
Carbon‐13 NMR relaxation studies of some dicyclohexyl compounds
Authors: Gillies Duncan G. , Matthews Stephen J. , Sutcliffe Leslie H.
Published: May 2005

Four dicyclohexyl compounds were studied, one of which is a traction fluid and the remainder have related structures in which the cyclohexane rings are separated by two or three carbon atoms. Carbon‐13 NMR T1 and NOE data were obtained for the four compounds at 22.50 and 100.62 MHz over a wide temperature range. The data were fitted simultaneously to either a reduced Lorentzian spectral density or to a ‘model‐free’ two‐correlation time spectral density. For the first time it has been possible to observe the tracking from the full ‘model‐free’ two‐correlation time spectral density to the reduced Lorentzian spectral density. From the correlation times and activation energies derived from these fittings, it can be concluded that all the compounds have semi‐rigid structures. Computer modelling of the structures and molecular mechanics calculations of the rotational barriers gave results in agreement with those from the NMR data. Similarly, it was found that the friction coefficients of the compounds correlate with the NMR and molecular mechanics conclusions, namely that the increased rigidity produced by the introduction of methyl groups into the linkage between the cyclohexane rings leads to a more effective traction fluids. Hence it seems to be feasible to design new traction fluids in the laboratory.
Monitoring site‐specific natural hydrogen isotope fractionation using a novel phosphorus‐containing chiral discriminating reagent
Authors: Hägele Gerhard , Boisnière Bruno , Helie Isabelle , Rabiller Claude , Martin Gérard J. , Martin Maryvonne L.
Published: May 2005

The synthesis of a novel chiral discriminating reagent, the ester resulting from the reaction of L‐menthylphenylphosphoryl chloride with ethanol, is reported. This reagent, C, is aimed to differentiate the R and S monodeuterated enantiomers of ethanol, which constitutes an important isotopic probe for mechanistic studies and origin inference of natural products. The proportions of the two P‐epimeric structures, CA and CB, which compose reagent C are directly accessible by 31P NMR. Analysis of 1D and 2D NMR spectra and theoretical simulations enable the 1H and 13C chemical shifts of CA and CB to be determined. The chemical shift differences exhibited by the methylenic hydrogens of the ethoxy moiety in CA and CB are of the order of 0.3 ppm. These large differences can be mainly attributed to ring current effects. Such effects have been estimated using two different methods on the basis of model conformations of the two epimers, CA and CB, deduced from energy minimization in a quantum mechanical approach. The relative signs of the chemical shift differences δR(C)—δS(C) associated with the pro‐R and pro‐S positions in the CA and CB isomers cannot be determined from the proton spectrum. The ring current calculations suggest that δR(C)—δS(C) are of opposite signs in the two P‐epimers. This interpretation, and consequently the conformational analysis, are supported by the 2H NMR study of a chiral discriminating ester prepared from ethanol selectively enriched in deuterium in the pro‐R position by stereospecific exchange reactions involving the enzymatic pair alcohol dehydrogenase–diaphorase. The chiral discriminating reagent, C, was then used for determining the enantiomeric imbalance in ethanol samples obtained from biosynthesis under different conditions, and site‐specific fractionation factors were calculated.
Conformational analysis of cembrenenol: Application of 1H and 13C NMR spectroscopy and of computational methods
Authors: Bigler P. , Bircher H. R. , Müller C. , Gerber P. R. , Gubernator K.
Published: May 2005

The solution structure of the cyclic diterpene cembrenenol was investigated. A strategy for conformational analysis is proposed which is based on computational methods and experiments to determine the structure‐relevant NMR parameters. Computed and experimentally determined steady‐state NOEs were compared in a first step, which served to sort out a few probable conformers. The detailed analysis of homo‐ and hetero‐nuclear coupling information together with NOE data defining local geometries allowed, in a second step, the selection of the most probable conformation. The structure corresponds to the lowest energy structure proposed by computational methods alone. Its ring structure is in excellent agreement with the x‐ray ring structure of the closely related cembrenene.
NMR of terminal oxygen. 6—17O NMR of the SO ‘double bond’: Derivatives of arylsulphinic and arylsulphonic acids
Authors: Dahn Hans , Van Toan Vien , Ung‐Truong My‐Ngoc
Published: May 2005

The 17O NMR spectra of terminal oxygen atoms in esters, anions and amides of substituted arenesulphinic acids and in esters and amides of substituted arenesulphonic acids were measured. The signals of the terminal O appear close to those of the bridge O. Compared with carbonyl O, terminal SO shows (a) a lower sensitivity to the electronic influences of geminal groups, (b) only a low sensitivity to arene ring substituents and (c) small solvent effects. The difference between C‐ and S‐bound O is discussed in terms of π‐bond character. Dy3+ complexation occurs with the terminal O in methyl arenesulphinates.
Synthesis and steric structure of cis‐ and trans‐alicycle‐fused dihydrothiazepines
Authors: Sohár P. , Újszászy K. , Szabó J. , Simon L. , Talpas G. S. , Fodor L. , Bernáth G.
Published: May 2005

β‐Lactam‐condensed saturated thiaazabicycles underwent ring transformation to give a new type of alicycle‐fused 3‐phenyl‐2‐methoxycarbonyl‐4,5‐dihydro‐1,4‐thiazepine. Oxidation of the cis and trans cyclohexane derivatives with perbenzoic acid furnished sulphones. The configurations and conformations of the new compounds were confirmed by 1H and 13C NMR spectroscopy, making use of DR, DNOE, DEPT and 2D HSC measurements.
A simple procedure for the determination of the quadrupole interaction parameters and isotropic chemical shifts from magic angle spinning NMR spectra of half‐integer spin nuclei in solids
Authors: Engelhardt Günter , Koller Hubert
Published: May 2005

A simple procedure is presented for the determination of the asymmetry parameter of the electric field gradient, the quadrupole coupling constant, the second‐order quadrupolar shift and the isotropic chemical shift of quadrupolar nuclei with half‐integer spin directly from the experimental magic angle spinning (MAS) NMR spectra of powder samples measured at a single magnetic field. General equations applicable to any half‐integer spin nucleus and the specific expressions for 23Na and 27 Al are given. The simple calculations can easily be performed with a pocket calculator and avoid any spectral simulation or lengthy computer work. The method was applied to a series of 23Na MAS NMR spectra of selected sodium compounds and the agreement of the results with those of computer simulations is demonstrated.
1H and 13C NMR study of some (E)‐3′‐and 4′substituted stilben‐4‐ols
Authors: Fisher Thomas H. , Schultz Tor P.
Published: May 2005

A series of ten (E)‐stilben‐4‐ols, HOPhCHCHPhX, with X = H, 4′‐Cl, 4′‐F, 4′‐Me, 4′;‐OMe, 3′‐Me, 3′‐OMe, 3′‐OH, 3′‐F and 3′,4‐diOMe, were studied using one‐ and two‐dimensional NMR techniques. Interpretation of these spectra led to definitive assignments of all carbon and hydrogen chemical shifts. 1H chemical shift increments were quantitatively determined for the five substituents studied, and the para Ai value of the styryl group was found to be more deshielding than those recorded in previous reports.
NMR spectroscopy of hexa‐ and octahydropyrazino [1′, 2′ : 1,2]pyrido [3,4‐b]indoles and 15‐azayohimbanes
Authors: Valls Nativitat , Segarra Victor M. , Bonjoch Josep
Published: May 2005

The 1H (200 MHz) and 13C (50.3 MHz) NMR spectra of some hexa‐ and octahydropyrazino[1′, 2′ : 1,2]pyrido‐[3,4‐b]indoles (1–13), 15‐azayohimbanes (15–18), and related compounds (14, 19, 20) are reported. The data have been analyzed in terms of the preferred conformation (9–13, 15–20) and configuration (15–20).
NMR investigations of forskolin. Complete assignment of proton and carbon NMR spectra and conformational analysis
Authors: Kogler Herbert , Fehlhaber Hans‐Wolfram
Published: May 2005

The 1H‐ and 13C NMR spectra of forskolin have been re‐investigated. Assignments are based exclusively on unambiguous carbon–carbon and carbon‐proton correlations derived from two‐dimensional NMR spectra. Stereo‐specific differentiations were deduced from selective proton NOE measurements and the interpretation of vicinal and long‐range proton‐proton scalar couplings. The proton‐proton distances calculated from proton NOE effects fit best with a flattened boat‐like conformation of ring C, which is different from the conformation of forskolin in the solid state.
Chemical modifications of phenoxy resin. Synthesis and 1H NMR study of model compounds
Authors: Fdez‐Berridi Maria J. , Iruin Juan J. , de Ilarduya Antton Martinez , de Gauna Asun Ruiz , Valero Miguel
Published: May 2005

The hydroxy group of phenoxy resin has been modified by etherification and esterification. The 1H NMR spectra of these products show large differences in the splitting patterns of the methylene protons according to the chemical nature of the substituent groups. Model compounds for phenoxy resin and derivatives, as well as some other glycerol derivatives, have been synthesized in order to study in more detail the signals of the CH2 group. The 1H NMR spectra of these compounds show two types of splitting. In some cases both protons absorb clearly as a doublet through accidental equivalence, while in other cases they are magnetically non‐equivalent. This behaviour can be explained by non uniform conformer populations (JAX ≠ JBX) in some cases, but where JAX ≈︁ JBX it could not be explained without taking into account the molecular asymmetry.
1H NMR spectroscopy of cycloadducts of 1,5‐ and 1,6‐diazaphenanthrene phenacylides
Authors: Śliwa Wanda , Bachowska Barbara , Postawka Anna
Published: May 2005

The 1H NMR spectra of cycloadducts of 1,5‐ and 1,6‐diazaphenanthrene phenacylides with acrylonitrile, ethyl acrylate, dimethyl acetylenedicarboxylate (DMAD), maleic anhydride and ethyl maleate, and those of cycloadducts of 1,5‐ and 1,6‐diazaphenanthrenes with DMAD, are presented.
Carbon‐13 NMR studies of some di‐and tetra‐substituted anthracene‐9,10‐dione derivatives related to the anti‐cancer drug mitoxantrone
Authors: Blanz Joachim , Mewes Kersten , Beth Meike , Zeller Klaus‐Peter , Ehninger Gerhard
Published: May 2005

Carbon‐13 NMR data of 18 di‐ and tetra‐substituted anthracene‐9,10‐dione derivatives related to the anticancer drug mitoxantrone.
1H and 13C NMR characterization of a new chiral porphyrin, meso‐Tetra(α, β, α, β‐o‐camphanylamidophenyl)porphyrin, and its rhodium(III) complex
Authors: Licoccia Silvia , Paci Maurizio , Tagliatesta Pietro , Paolesse Roberto , Antonaroli Simonetta , Boschi Tristano
Published: May 2005

The synthesis of a new chiral porphyrin, meso‐tetra(α, β, α, β‐o‐camphanylamidophenyl)porphyrin, and its Mn(III) and Rh(III) derivatives is reported. Complete resonance assignments of both the 1H and 13C spectra of the ligand has been achieved via homo‐ and hetero‐nuclear 2D NMR. Insertion of metal ions into the porphyrin ring was performed both in order to test the catalytic properties of the resulting complexes and to characterize the effect of of metal coordination on the spatial distribution of the bulky substituents. The Mn complex was then tested in catalytic chiral epoxidation reactions, giving low enantiomeric excesses (20%). The 2D NMR spectra of the Rh derivative indicate the existence of four molecular species generated by the interaction of the metal atom with the peripheral substituents of the porhyrin ring. In fact, a complex combination of axial coordination, together with the chirality of the camphanyl substituents, removed the symmetry of the porphyrin plane.
Studies of two‐dimensional 113Cd1H overhauser effect spectra
Authors: Yan Xin , Fan Jinsong , Xu Xiaolong , Wang Dehua , Nie Guojun , Qian Baogong
Published: May 2005

The two‐dimensional 113Cd1H Overhauser effect spectra of some cadmium compounds are reported. The results show that the two‐dimensional 113Cd1H Overhauser effect experiments can be used to investigate the intramolecular and intermolecular interactions and structures of cadium compounds.
Studies of tautomerism and protonation in 2‐aryl‐1H‐imidazo[1,2‐a]imidazole derivatives using 1H and 13C NMR
Authors: Liu Maili , Farrant R. Duncan , Glen Robert C. , Lindon John C. , Barraclough Paul , Smith Steven
Published: May 2005

The tautomerism and protonation of the putative inotropic 2‐(2′,4′‐dimethoxy)phenyl‐1H‐imidazo[1,2‐a]imidazole (2) has been studied in several solvents by comparing its 1H and 13C chemical shifts with those of its 1‐ and 7‐methyl derivatives 3 and 4, respectively, and acid salts. Tautomer and rotamer populations were also estimated from measurements of proton relaxation rates and NOE effects. Heterocycle 2 exists predominantly as the 1H‐tautomer in CDCl3, but as the 7H‐tautomer in DMSO‐d6 and methanol‐d4–D2O solutions. In CDCl3 solution, 2 appears to exist with the N‐1‐H and 2′‐OMe groups adjacent, but in DMSO‐d6 the conformation is the rotated form with N‐7‐H and H‐6′ adjacent; 3 exists as a mixture of rotamers in CDCl3 and in DMSO‐d6 whereas 4 is in the form with the N‐7‐Me and H‐6′ adjacent in both solvents. The observed conformational preferences have been compared with the results of semi‐empirical molecular orbital calculations and found to be in broad agreement. Protonation of 2 occurs mainly at N‐1 in DMSO‐d6 and at N‐7 in CDCl3, as expected from observed tautomeric ratios in the free base.
One‐bond 13C13C spin–spin coupling in cubanes
Authors: Axenrod T. , Liang B. , Bashir‐Hashemi A. , Dave P. R.
Published: May 2005

Endocyclic one‐bond 13C13C spin–spin coupling constants in a series of cubane derivatives were recorded. The values measured using the INADEQUATE pulse sequence were found to be insensitive to the nature of the substituent, fall in a narrow range (27–30 Hz) and are comparable to values reported for similar cyclobutane derivatives.
Two‐dimensional NMR and 13C spin—lattice relaxation study of methyl fluorene‐3‐carboxylate
Authors: Pissas D. , Dais Photis , Sauriol Francoise
Published: May 2005

13C nuclear magnetic relaxation rates were measured as a function of temperature for methyl fluorene‐3‐carboxylate and used to describe the dynamics of this molecule. The easiest reorientation is about the x principal diffusion axis, which is situated close to that inertial principal axis corresponding to the smallest moment of inertia. The reorientation of this planar asymmetric rotor is found to be anisotropic about the in‐plane x and y axes, as expected from unequal moments of inertia. The reorientation about the out‐of‐plane axis z is faster at the lowest temperature measured and it becomes comparable to the in‐plane motion at the remaining temperatures, showing decreased frictional forces for rotation in the molecular plane. Total assignment of the 1H and 13C NMR spectra of the fluorene derivative was achieved by employing 1D and 2D NMR techniques.
Yttrium(III) oxoisopropoxide: A new synthetic route and reinvestigation of the 1H, 13C and 89Y NMR of Y5(μ5‐O)(μ3‐OiPr)4(μ2‐OiPr)4(O iPr)5
Authors: Page Catherine J. , Sur Sandip K. , Lonergan Mark C. , Parashar Gyanendra K.
Published: May 2005

Yttrium(III) oxoisopropoxide, Y5O(OiPr)13, was synthesized via a new synthetic route and characterized by mass spectrometry and multinuclear magnetic resonance spectroscopic techniques. Extensive 1H, 13C and 89Y NMR studies with full assignments are reported.
13C NMR spectra of some 3‐substituted cycloalkanespirohydantoins and their 4‐hydroxy derivatives
Authors: Pedregal C. , Espada M. , Albert J. , Cruz E. , Virgili A.
Published: May 2005

13C NMR data for 21 cycloalkanespiro‐hydantoin derivatives, substituted at position 3, are reported and compared with those for the corresponding 4‐hydroxy derivatives.
Platinum‐phosphine cluster chemistry: New potentials from 195Pt‐31P{1H} triple‐resonance spectroscopy
Authors: Rüegger Heinz , Moskau Detlef
Published: May 2005

Platinum‐phosphorus heteronuclear multiple‐quantum coherence spectroscopy has been employed for the characterization of platinum‐phosphine cluster compounds. Rules are developed for the interpretation of these spectra, whose appearance depends on the chosen pulse‐sequence, phase‐cycling and whether direct or remote platinum‐phosphorus coupling constants have been selected. Spectral editing according to the different isotopomers (with respect to 195Pt) is possible when complete evolution of multiple‐quantum coherence is allowed. This method offers a substantial advantage in the characterization of larger cluster compounds.
EPR investigation of the second sphere coordination of [Cr(CN)5(NO)]3− with protonated polyethyleneimine
Authors: Chandramouli G. V. R. , Schläpfer C. W. , von Zelewsky A.
Published: May 2005

The second sphere coordination of protonated, branched polyethleneimine (PEI) with [Cr(CN)5(NO)]3− (CPN) was studied by EPR spectroscopy. The interaction between the CPN complex ion and protonated PEI is reported as a function of pH. Simulation of the spectra indicated that ca. 98% of the CPN is bound to the polymer at pH ≈︁ 7. The tumbling rate of this species was determined by simulation as 1/τc = 1 × 10−8 s−1. The binding of CPN by PEI was influenced by the addition of other salts. Exchange interaction between Cu2+ and CPN was observed on the simultaneous binding of these two paramagnetic species to PEI. The pH dependence of the exchange was measured. At an intermediate pH range (7–9), CPN binds in the second and Cu2+ in the first sphere. The exchange interaction increases with the ‘loading’ of the polymer with the two paramagnetic species. Based on these results, a model is proposed for the species in solution.
15N NMR study of the linkage isomerism of pentaammine(glycinato)rhodium(III)
Authors: Appleton Trevor G. , Cox Matthew R.
Published: May 2005

Refluxing a solution of [Rh(NH3)5(gly‐O)]2+ at pH 10 produces [Rh(NH3)5(gly‐N)]2+ (glyH = glycine, +NH3CH2CO2−). 15N NMR spectra of reaction mixtures obtained with either 14N or 15N isotopes present in the ammine or glycinate ligands are consistent only with the O‐ to N‐isomerization reaction being intramolecular. The analogous β‐alaninate complex does not isomerize under similar conditions.
Inverse two‐dimensional 31P, 103Rh{1H}NMR of cationic rhodium(I) complexes containing chelating diphosphines
Authors: Ernsting J. M. , Elsevier C. J. , De Lange W. G. J. , Timmer K.
Published: May 2005

A series of new and known Rh(I) complexes [Rh(R2P(CH2)nPR2)2]Y and [Rh(diene)(R2P(CH2)nPR2)]Y (R = Me, Et, Ph, C6F5, C6H4CF3; Y = Cl, ClO4, PF4, BF4, OSO2CF3; diene = norbornadiene, cyclooctadiene) were prepared and their 103Rh NMR spectra were recorded on a 100‐MHz spectrometer by using inverse two‐dimensional 31P, 103Rh{1H} NMR. This technique provides quick access to 103Rh NMR data (2–8 h for ca. 0.1 M samples) when dealing with Rh‐phosphine complexes. The 103Rh NMR data are discussed. All δ(103Rh) of the cationic Rh(I) complexes appear at the lower frequency end of the Rh(I) range, i.e. between −1350 and + 200 ppm, which is in agreement with the fact that the Rh shift is determined by σp and with a large ΔE in square‐planar d8 complexes. The relative change in ΔE between complexes is not large and the changes in paramagnetic shift for these complexes are essentially determined by their relative σ‐donor capacities. δ(103Rh) shows an inverse correlation with δ(31P), which was rationalized by invoking the chelate ring size containing the Rh centre and the bidentate phosphine ligands.
1H and 13C NMR spectra, 13C NMR relaxation times and molecular modelling studies of the narcotic agonist–antagonist α‐( − )‐N‐propynylnormetazocine
Authors: Amato Maria E. , Grassi Antonio , Pappalardo Giuseppe C. , Machytka Daisy , Radics Lajos
Published: May 2005

The analysis of high‐frequency 1H and 13C NMR spectra and both 1H1H homonuclear and 1H13C heteronuclear chemical shift correlation experiments indicate that N‐propynlnormetazocine (NPMH+) is configurationally heterogeneous in solution, with the N‐equatorial isomer being more populated than the N‐axial isomer. The experimental proton–proton coupling constants measured for both diastereoisomers were in agreement with the calculated values for a chair conformation of the piperidine ring. AM1 and MM2 theoretical calculations both indicated the chair conformation as that preferred by the piperidine ring, and the N‐equatorial isomer as being energetically favoured with respect to the N‐axial form. The best fit of the 13C T1 relaxation time data and the related motional analysis of NPMH+ was carried out using the anisotropic model of reorientation with superimposed internal motion. The results showed an increase of the rotational anisotropy of the molecule on passing from the gas phase to the solution state.
Solid‐state 2H NMR study of the dynamics of the methoxy groups in perdeuteriated bis(dimethoxythiophosphoryl) disulphide
Authors: Potrzebowski Marek J.
Published: May 2005

2H solid‐state NMR was employed to study the statio and dynamic properties of perdeuteriated bis(dimethoxythiophosphoryl) disulphide. It was found that sample preparation has a significant influence on the line shapes of the broad‐line solid‐state spectra. It was concluded from inversion–recovery experiments that the methyl groups are in the fast exchange regime, τc < 10−s s. The three‐site jump model, with reorientation of the methyl group about a C3 symmetry, was assumed as the best explanation of the T1 anisotropy. The apparent activation energy calculated from an Arrhenius plot was found to be 5.35 kJ mol−1.
Carbon‐13 NMR spectra of some 2‐ ethylthio‐4′‐substituted acetophenones and their mono‐ and di‐oxygenated derivatives
Authors: Olivato Paulo Roberto , Bonfada Élida , Rittner Roberto
Published: May 2005

The 13C NMR signals for some 2‐ethylthio‐, 2‐ethylsulphinyl‐ and 2‐ethylsulphonyl‐4′‐substituted acetophenones were assigned. The carbonyl carbons exhibit a progressive upfield shift on going from the ketosulphides to the ketosulphoxides and to the ketosulphones. The α‐methylene carbons fro the three classes of compounds are shielded by almost the same amount in relation to the corresponding calculated values. The chemical shifts of the aromatic ring carbons are in close agreement with those calculated using substituent chemical shifts.
1H and 13C high‐resolution NMR analysis of a siloxane polymer with phenyl benzoate side‐chains
Authors: Findeisen M. , Roth H.
Published: May 2005

The peaks have been assigned in the 1H NMR spectrum (250 MHz) and in the 13C NMR spectrum in solution of polysiloxane with phenyl benzoate side‐chains.
19F, 14N and 15N NMR spectroscopic studies on triazadienyl fluoride, N3F
Authors: Schatte Gabriele , Willner Helge , Willert‐Porada Monika
Published: May 2005

The results of 19F, 14N and 15N NMR measurements for all 14N/15N isotopomers of N3F in CD2Cl2 solution are reported. Substantial deshielding for the N‐α and N‐γ atoms, relative to other covalent azides XN3 (X  Cl, H, CF3, etc.), is observed. The coupling constants also indicate unusual bonding in N3F. 1J(15N‐α, F) and 3J(15N‐γ, F) are similar (58.2 and 58.6 Hz, respectively), very small for a 1J(15NF) but very large for a 3J(15NF) value. The observed value of 26.5 Hz for 1J(15N‐α 15N‐β) is the largest, and 2J(15N‐α 15N‐γ) (5.3 Hz) is the first reported coupling constant for an azide. The unusual N3F NMR data are discussed in terms of calculated atomic charges and the influence of the paramagnetic term which dominates the chemical shifts. This term expresses the deshielding due to the circulation of electrons in the magnetic field between the HOMOs and the LUMOs.
Magnetic field‐dependent nuclear spin–spin coupling
Authors: Raynes William Thomas , Stevens Sarah Jane
Published: May 2005

As the magnetic fields used in NMR spectrometers become greater, it is expected that a field dependence of nuclear spin–spin coupling will be observed. A part of this, which would be independent of temperature, is due to the contributions of higher terms in the Hamiltonian of the molecule in the external magnetic field and the two nuclear spin operators. Perturbation theory at second, third and fourth order is used to extract the general features of these higher order terms. Contributions are due (a) to diamagnetic and paramagnetic terms of each of the four familiar parts of the spin coupling— Fermi contact, spin–dipolar, and orbital paramagnetic and orbital diamagnetic, and (b) to cross‐terms determined by operators for the diamagnetic and paramagnetic shielding at the two coupled nuclei. Explicit expressions are presented for the more important contributions. It is estimated for strongly magnetic nuclei in large molecules that the coupling varies as 0.5 × 10−5 B2 Hz, so that a field of about 14 T should produce a change in the coupling of 0.001 Hz. These are, respectively, the field used in high‐field NMR spectrometers and the upper limit of precision in the measurement of spin–spin coupling constants at the present time.
ENDOR and EPR studies on polycyclic aromatic radical cations
Authors: Sang Hong , Wang Hanqing , Such K. P. , Jent F.
Published: May 2005

Several polycyclic aromatic radical cations produced in Friedel–Crafts alkylation reactions were studied by EPR and ENDOR methods, and the following were identified: 1,2,5,6‐tetramethylanthracene, 2,3,6,7,9,10‐hexamethylanthracene, 3,6,11,14‐tetramethyldibenzo [a,c]triphenylene and 2,6,9,10‐tetramethylanthracene radical cations.
31P Hyperfine interaction in a new type of phosphorus‐containing iminoxy free radicals. An ESR study
Authors: Siatecki Zdzislaw , Chmielewski Piotr J. , Jezierski Adam
Published: May 2005

Iminoxy radicals of a new type, having the general formula RC(NO˙)P(O)(OEt)2, were synthesized and characterized by means of ESR spectroscopy. The presence of two isomers due to the different position of the CNO˙ fragment with respect to the R substituent and the P atom, and the relative stability of the isomers, was established. The influence of the R substituent on the relative population of the isomers was found. The nitrogen hyperfine constants for the isomers differ by about 10%, while the phosphorus hyperfine constant for the less populated isomer is about six time greater, reaching a value of 60 G. A linear correlation was found between the values of this hyperfine constant and Dimroth–Reichardt ET(30)solvent parameters. The solvent dependence of the 31P hyperfine constant was shown to be stronger than the dependence found for the 14N hyperfine constant of nitroxides and iminoxyls.
13C NMR chemical shift assignments for substituted 2‐azabicyclo[3.3.1] nonan‐7‐ones
Authors: Casamitjana Núria , Bonjoch Josep , Gràcia Jordi , Bosch Joan
Published: May 2005

The 13C NMR spectra of 26 substituted 2‐azabicyclo[3.3.1]nonan‐7‐ones are reported, providing a diagnostic method for the stereochemical elucidation of the relative configuration of these products.
1H and 13C NMR spectra of the reverse transcriptase inhibitor (+)‐(S)‐4,5,6,7‐tetrahydroimidazo‐9‐chloro‐5‐methyl‐6‐(3‐methylbut‐2‐enyl)imidiazo[4,5,1‐jk] [1,4]benzodiazepin‐2(1H)‐thione (TIBO)
Authors: Leo Gregory C. , Gauthier A. Diane , Caldwell Gary W. , Kukla Michael J.
Published: May 2005

Proton and carbon NMR chemical shift assignments for (+)‐(S)‐4,5,6,7‐tetrahydroimidazo‐9‐chloro‐5‐methyl‐6‐(3‐methylbut‐2‐enyl)imidazo[4,5,1‐jk][1,4] benzodiazepin‐2(1H)‐thione (TIBO) were made based on 1D and 2D NMR measurements at 9.4 T.
NMR multinuclear study (13C, 14N, 17O) of indane‐1,3‐diones
Authors: Petrova M. V. , Liepiņš E. , Pauliņš J. , Gudriniece E.
Published: May 2005

13C, 17O and 14N NMR chemical shift data for a series of 1,3‐indandiones are reported. Linear correlations were established between some chemical shifts and the electron densities for the compounds in question. Chemical reactivity predictions were based on the results obtained.
1H, 13C and 17O NMR study of chlorovanillins and some related compounds
Authors: Kolehmainen Erkki , Laihia Katri , Knuutinen Juha , Hyötyläinen Juha
Published: May 2005

1H, 13C and 17O NMR chemical shifts and nJ(H,H), 1J(C,H) and 3J(C‐6, H‐formyl) spin—spin coupling constants of chlorinated vanillins (3‐methoxy‐4‐hydroxybenzaldehydes) were determined. The variation in the long‐range 4J(H,H) value between the formyl proton and an ortho‐proton suggests that the ortho‐substituent strongly forces the formyl group out of the aromatic plane. This can also be observed by considering the 3J(C‐6,H‐formyl) values and the 13C and 17O NMR chemical shifts. The 17O NMR chemical shifts show a linear correlation with the torsion angle of the formyl group calculated by molecular mechanics. The 13C and 17O NMR chemical shifts of the methoxyl group also possess strong predictive power in estimating the torsional characteristics of this group.