bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multinuclear magnetic resonance study of Li2OSiO2 SolGel glasses
Authors: Dupree Raymond , Holland Diane , Mortuza Mohamed Golam , Smith Mark Edmund , Chen Aihu , James Peter F. 
Published: May 2005

AbstractA multinuclear magnetic resonance study of some solgel prepared Li2OSiO2 glasses and of their crystallization is presented. The glasses, all of which have been heated to 400°C, are found to contain a large amount (ca. 20 mol‐%) of H2O, mostly in the form of OH. The local structure is very different from melt‐formed glasses in that the major modifier is H2O rather than Li2O, with the formation of Si(OSi)3OH units. The glasses start to crystallize at a lower temperature than melt‐formed glasses, with the first crystalline product being lithium metasilicate even for very silica rich sol‐gel compositions.
A pulse sequence for the measurement of short spin‐lattice relaxation times for carbon‐13 in solid polymers
Authors: Findlay Anita , Harris Robin K. 
Published: May 2005

AbstractA pulse sequence is presented which allows measurement of short T1 values (< 1 s) in solids, avoiding probe damage by the use of saturating sequences of 90° pulses. The use of the sequence is illustrated for a cross‐linked polymeric system which contains composite peaks having both short‐T1 and long‐T1 components.
Complete proton and carbon spectral assignments of acrihellin and hellebrigenin
Authors: Müller Arndt , Nonnenmacher Gerhard , Kutscher Bernhard , Engel Jürgen 
Published: May 2005

AbstractThe complete assignment of all 1H and 13C NMR signals of acrihellin in chloroform solution is presented. The analysis of the 1H and 13C NMR spectra was performed using the heteronuclear 2D NMR techniques H,C‐COSY and H,C‐COLOC. For an unambiguous assignment of the 13C NMR spectrum the elucidation of carbon–carbon connectivities via 2D‐INADEQUATE was most important. The INADEQUATE experiment was also applied to hellebrigenin in DMSO‐d6 solution. This experiment confirmed a recently published carbon assignment.
Assignment of quaternary carbon resonances in lambertellin by soft heteronuclear multiple bond correlation
Authors: Keniry Max A. , Poulton Gerald A. 
Published: May 2005

AbstractA one‐dimensional version of the heteronuclear multiple bond correlation experiment (HMBC) is shown to be an excellent alternative to the full two‐dimensional experiment when the carbon resonances are well resolved. The quaternary resonances of lambertellin, a metabolite of Ciboria gordonii Funk, are correlated to the previously assigned proton resonances by selective transfer of zero and double quantum coherence to observable proton magnetization by a frequency‐selective carbon decoupler pulse.
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

AbstractTwo‐ 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

Abstract77Se–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

AbstractCoherence 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

AbstractThe 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

AbstractThe 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

AbstractSolid‐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

AbstractThe 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

AbstractThe 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

AbstractDuring 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

AbstractNitrogen‐15 chemical shifts of 1,2‐diaminobenzenes, 1,8‐diaminonaphthalenes and their monoprotonated species are reported.
NMR examination of tricyclo[4.2.0.01,3]octane
Authors: Smith William B. , Brinker Udo H. 
Published: May 2005

AbstractThe 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

AbstractSingle 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

AbstractThe 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

Abstract1H 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

AbstractNatural 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

AbstractThe 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

AbstractThe 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

AbstractFrom 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

AbstractCarbon‐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

AbstractThe 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

Abstract39K 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

AbstractNorbornane‐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

AbstractAn 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

AbstractPolycrystalline 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

AbstractEstablished 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

AbstractThe 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

AbstractFour 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.