scholarly journals [AU(DIEN)Cl]Cl2: Exchange Phenomena Observed by H1 and C13 NMR Spectroscopy

1999 ◽  
Vol 6 (4-5) ◽  
pp. 261-269 ◽  
Author(s):  
Sabine L. Best ◽  
Zijian Guo ◽  
Milos I. Djuran ◽  
Peter J. Sadler
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
Hydroxo Complex ◽  
Acidic Solutions ◽  
Exchange Effects ◽  
Square Planar ◽  
Ph Range ◽  
Solution Behaviour

The solution behaviour of the square-planar gold(III) complex [Au(dien)Cl]Cl2 (dien = 1,5- diamino-3-azapentane) was investigated by H1 and C13 NMR spectroscopy. We have found that H1 NMR spectra of [Au(dien)Cl]Cl2 are characterised by exchange behaviour over the whole pH range, and some exchange effects are also seen in C13 NMR spectra of the deprotonated hydroxo derivative of the complex in alkaline solution. An exchange rate of > 378 s-1 was determined from H1 NMR spectra at pH∗2 (coalescence temperature 40C° ). In slightly acidic solutions of the complex, H1 chemical shifts are in accordance with the known deprotonation of the central amine group of the complexed diethylenetriamine ligand. In C13 NMR spectra, two separate sets of resonances are observed for the chloro and the hydroxo complex of gold(III) diethylenetriamine. The hydroxo complex [Au(dien-H)OH]+ shows exchange effects in C13 NMR spectra. Variable temperature studies show the carbon atoms next to the central secondary amine to be inequivalent and each present in two different environments that are in intermediate to fast exchange on the NMR time-scale.

scholarly journals Spin State Behavior of A Spin-Crossover Iron(II) Complex with N,N′-Disubstituted 2,6-bis(pyrazol-3-yl)pyridine: A Combined Study by X-ray Diffraction and NMR Spectroscopy

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 793
Author(s):  
Elizaveta K. Melnikova ◽  
Dmitry Yu. Aleshin ◽  
Igor A. Nikovskiy ◽  
Gleb L. Denisov ◽  
Yulia V. Nelyubina
Keyword(s):  
Nmr Spectroscopy ◽  
Spin State ◽  
Metal Ion ◽  
Spin Crossover ◽  
Molecular Design ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
High Spin State ◽  
X Ray Diffraction ◽  
X Ray

A series of three different solvatomorphs of a new iron(II) complex with N,N′-disubstituted 2,6-bis(pyrazol-3-yl)pyridine, including those with the same lattice solvent, has been identified by X-ray diffraction under the same crystallization conditions with the metal ion trapped in the different spin states. A thermally induced switching between them, however, occurs in a solution, as unambiguously confirmed by the Evans technique and an analysis of paramagnetic chemical shifts, both based on variable-temperature NMR spectroscopy. The observed stabilization of the high-spin state by an electron-donating substituent contributes to the controversial results for the iron(II) complexes of 2,6-bis(pyrazol-3-yl)pyridines, preventing ‘molecular’ design of their spin-crossover activity; the synthesized complex being only the fourth of the spin-crossover (SCO)-active kind with an N,N′-disubstituted ligand.

13C-Chemische Verschiebungen von Aminosäuren und Peptiden / 13C-NMR Chemical Shifts of Amino Acids and Peptides

1971 ◽  
Vol 26 (3) ◽  
pp. 213-222 ◽  
Author(s):  
Wolfgang Voelter ◽  
Günther Jung ◽  
Eberhard Breitmaier ◽  
Ernst Bayer
Keyword(s):  
Amino Acids ◽  
Fourier Transform ◽  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Analytical Tool ◽  
Reasonable Time ◽  
C Isotopes ◽  
Direct Recording ◽  
C Nmr

Pulse - Fourier - Transform-13C-NMR spectroscopy allowed the direct recording of 13C-NMR spectra of amino acids and peptides with natural abundance of 13C isotopes within a reasonable time. The 13C-signals of more than 50 free and protected amino acids and several peptides were assigned. 13C-NMR spectroscopy gives valuable information about the carbon skeleton, thus offering a new analytical tool for the study of biopolymers and their constituents.

Chemical shift correlated two-dimensional nmr spectroscopy and its application to solving the proton nmr spectra of oligoribonucleotides

1980 ◽  
Vol 58 (18) ◽  
pp. 1947-1956 ◽  
Author(s):  
Alex D. Bain ◽  
Russell A. Bell ◽  
Jeremy R. Everett ◽  
Donald W. Hughes
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Nmr Spectra ◽  
Pulse Sequence ◽  
Chemical Shifts ◽  
Proton Nmr ◽  
Two Dimensional

An alternative two-dimensional nmr pulse sequence, (90°–t1/2–90°–t1/2–FID),correlates the chemical shifts of coupled nuclei. The application of this technique to the solution of the complicated proton nmr spectra of oligoribonucleotides is discussed.

Mechanism of the lithium–iodine exchange in an iodothiophene

2005 ◽  
Vol 83 (9) ◽  
pp. 1577-1587 ◽  
Author(s):  
Hans J Reich ◽  
Wesley L Whipple
Keyword(s):  
Nmr Spectroscopy ◽  
Exchange Reaction ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Activation Parameters ◽  
Kinetic Scheme ◽  
Hypervalent Iodine ◽  
Metal Exchange ◽  
Complex Lithium

Solutions of 2-lithio-5-methylthiophene (4) were characterized using DNMR techniques and shown to be a mixture of monomer and dimer in THF–Et2O (3:2). The hypervalent iodine ate complex 5 (Ar2I–Li+), a presumed intermediate in the Li–I exchange with 2-iodo-5-methylthiophene, was observed by 13C and 7Li NMR spectroscopy at low temperatures (–130 °C). At higher temperatures, the ate complex coalesced with 2-lithio-5-methylthiophene. A kinetic scheme was developed, which accounts for the exchange of the monomer 4M, dimer 4D, and 2-iodo-5-methylthiophene (6) with the ate complex 5. The rates of the various exchanges were obtained through a DNMR analysis of the variable temperature 13C and 7Li NMR spectra, and the thermodynamic and activation parameters were calculated. The monomer 4M and the ate complex 5 have similar reactivity as aryl donors in the Li–I exchange reaction, but 4M is at least 1000 times as reactive as the dimer 4D towards the iodide.Key words: halogen–metal exchange, lithium iodinate, iodine ate complex, lithium reagent, aggregate reactivity.

1H NMR Spectrum: A Team-Based Tabletop Game for Molecular Structure Elucidation

2020 ◽  
Author(s):  
Zachary Thammavongsy ◽  
Michael A. Morris ◽  
Renee Link
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
1H Nmr Spectra ◽  
Molecular Formula ◽  
College Level ◽  
Nmr Spectrum ◽  
Laboratory Course

The 1H NMR Spectrum game, the first example of a team-based tabletop game focused on elucidating the structures of organic small molecules using 1H NMR spectra, was developed and deployed in a college level organic chemistry lecture course and laboratory course. The tabletop game was designed as a collaborative and competitive group activity to encourage multiple rounds of play to help students reinforce their 1H NMR spectra interpretation skills. While playing in either team-based or free-for-all mode, students analyzed the provided chemical shifts, splitting patterns, integrations, and molecular formula within a designated time limit to correctly deduce the structure associated with the 1H NMR spectrum. After playing the game, students in a lecture course and a laboratory course self-reported that they felt more comfortable solving 1H NMR spectroscopy questions, found the game to be an appealing study aid, and were able to complete multiple rounds of play to strengthen their skills in interpreting 1H NMR spectra. The 1H NMR Spectrum tabletop game may serve as an engaging and competitive group learning tool to supplement teaching on 1H NMR spectroscopy.

1H NMR Spectrum: A Team-Based Tabletop Game for Molecular Structure Elucidation

2020 ◽  
Author(s):  
Zachary Thammavongsy ◽  
Michael A. Morris ◽  
Renee Link
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
1H Nmr Spectra ◽  
Molecular Formula ◽  
College Level ◽  
Nmr Spectrum ◽  
Laboratory Course

The 1H NMR Spectrum game, the first example of a team-based tabletop game focused on elucidating the structures of organic small molecules using 1H NMR spectra, was developed and deployed in a college level organic chemistry lecture course and laboratory course. The tabletop game was designed as a collaborative and competitive group activity to encourage multiple rounds of play to help students reinforce their 1H NMR spectra interpretation skills. While playing in either team-based or free-for-all mode, students analyzed the provided chemical shifts, splitting patterns, integrations, and molecular formula within a designated time limit to correctly deduce the structure associated with the 1H NMR spectrum. After playing the game, students in a lecture course and a laboratory course self-reported that they felt more comfortable solving 1H NMR spectroscopy questions, found the game to be an appealing study aid, and were able to complete multiple rounds of play to strengthen their skills in interpreting 1H NMR spectra. The 1H NMR Spectrum tabletop game may serve as an engaging and competitive group learning tool to supplement teaching on 1H NMR spectroscopy.

Some Applications of Ultrahigh Resolution 15N NMR Spectroscopy

1998 ◽  
Vol 53 (4) ◽  
pp. 411-415 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Ēriks Kupče
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Absolute Magnitude ◽  
Natural Abundance ◽  
Coupling Constants ◽  
15N Nmr ◽  
Ultrahigh Resolution ◽  
Tert Butyl ◽  
15N Nmr Spectroscopy

Abstract Ultrahigh resolution 15N NMR spectra were measured for two nitroalkanes (MeNO2 la, tBuNO2 1c), two isocyanates (tBuNCO 2c, Me3SiNCO 2d), four isothiocyanates (MeNCS 3a, EtNCS 3b, tBuNCS 3c, Me3SiNCS 3d), one carbodiimide (Me3SiNCNSiMe3 4d), one keteneimine [Me3SiNCC(SiMe3)2 5d], two sulphinyl imides (tBuNSO 6c, Me3SiNSO 6d), and N-tert-butyl-pyrrole 7c, in order to determine coupling constants J(15N ,I3C) and isotope induced chemical shifts 1∆12/13C (15N) at the natural abundance of the isotopes. The values 1∆12/13C (15N) can be separated into two groups, one dealing with NC single and another one with NC double bonds. In each group (with few exceptions), the values 1∆12/13C (15N) become more negative with a decrease in the absolute magnitude of l1J(l5N ,13C)l. The corresponding values 1∆14/15N (13C) show a sim ilar behaviour. However, N-substituted pyrroles appear to be exceptional in this respect.

Analysis of oligosaccharides. 29Si and 13C NMR spectra of pertrimethylsilylated oligosaccharides derived from xylopyranose

1987 ◽  
Vol 52 (6) ◽  
pp. 1501-1513 ◽  
Author(s):  
Eva Petráková ◽  
Jan Schraml ◽  
Ján Hirsch ◽  
Magdalena Kvíčalová ◽  
Jan Zelený ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Parent Compound ◽  
Hydroxyl Groups ◽  
13C Nmr Spectra ◽  
Polyfunctional Compounds

29Si and 13C chemical shifts are reported for a series of 30 pertrimethylsilylated oligosaccharides containing xylopyranosyl unit. The number of lines in 29Si NMR spectra is in all cases in agreement with the number of hydroxyl groups present in the parent compound prior to trimethylsilylation. The results demonstrate the usefulness of 29Si NMR spectroscopy for the analysis of oligosaccharides and other polyfunctional compounds. The validity of direct additivity of 13C chemical shifts is tested on some model trisaccharides.

Carbon-13 nuclear magnetic resonance spectra of E-silyl-alkenes

1980 ◽  
Vol 58 (4) ◽  
pp. 361-368 ◽  
Author(s):  
Constantinos A. Tsipis ◽  
Constantinos A. Tsoleridis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Quantitative Analysis ◽  
Nmr Spectroscopy ◽  
Carbon Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr

Carbon-13 nmr chemical shifts of a number of E-silyl-alkenes containing the silyl substituent at an sp2 carbon atom are presented. Assignments of the chemical shifts have been made by noting systematic variations in the spectra with changes in substituents and by comparison of the chemical shifts to those of the corresponding unsubstituted alkenes. The substituent effects observed were explained on the basis of the π-acceptor ability of the silyl substituents and the structure of the molecules. Comparing the 13C nmr spectra of the E-silyl-alkenes and those of the corresponding unsubstituted alkenes, differential chemical shifts have been obtained which can be used as empirical substituent parameters for the prediction of the 13C nmr spectra of other E-silyl-alkenes not yet studied. It was also demonstrated that 13C nmr spectroscopy can be used without resorting to special techniques (gated decoupling and the addition of paramagnetics) as an alternative method to the 1H nmr for the quantitative analysis of mixtures of regio-isomer E-silyl-alkenes.

Zinn(IV)-Verbindungen mit Ferrocenylchalkogenat- und Ferrocenylendichalkogenat-Liganden. Synthese und Multikern-NMR-Spektroskopie / Tin(IV) Compounds Containing Ferrocenyl Chalcogenate and Ferrocenylene Dichalcogenate Ligands. Synthesis and Multinuclear NMR Spectroscopy

1993 ◽  
Vol 48 (7) ◽  
pp. 940-950 ◽  
Author(s):  
Max Herberhold ◽  
Michaela Hübner ◽  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectroscopy ◽  
Systematic Study ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Spiro Compounds ◽  
Coupling Constants ◽  
Solution Nmr ◽  
Multinuclear Nmr Spectroscopy ◽  
Cp Mas Nmr ◽  
Sulfur Containing

A series of tin(IV) compounds containing ferrocenyl chalcogenate (FcE) and ferrocenylene dichalcogenate (fcE2) ligands (E = S, Se, Te) has been synthesized for a systematic study of the NMR spectra with particular emphasis on 13C, 119Sn, 77Se and 125Te NMR. All compounds are formally derived from tetramethylstannane, SnMe4, by stepwise replacement of methyl by either FcE or fcE2 ligands. Starting from lithioferrocene the products are tetrasubstituted stannanes Me4-nSn(EFc)n (n = 1 and 2, E = S, Se, Te; n = 3 and 4, E = S, Se). Starting from 1,1′dilithioferrocene, the products are 1,1′-disubstituted ferrocenes such as fc(E-SnMe3)2 (E = S, Se, Te), although 1,3-dichalcogena[3]ferrocenophane rings are formed whenever possible to give [3]ferrocenophanes fcE2SnMe2 (E = S, Se, Te) and fc[E-Sn(Me)E2fc]2 (E = S, Se) or tin spiro compounds Sn(E2fc)2 (E = S, Se, Te). Whereas all (8) possible sulfur-containing and all (8) selenium-containing products were accessible, some of the tellurium-rich compounds could not be isolated due to preferred formation of either Fc2Te2 or fcTe3.All compounds were characterized on the basis of their 1H, 13C, 119Sn and, if possible, 77Se and 125Te solution NMR spectra. In many cases, coupling constants such as 2J(119Sn1H), nJ(119Sn13C) (n = 1,2,3), 1J(119Sn77Se) and 1J(125Τe119Sn), 1J(77Se13C) and 1J(125Te13C) could be determined. The δ119Sn chemical shifts of analogous phenyl and ferrocenyl compounds, Me4-nSn(EPh) and Me4-nSn(EFc)n (n = 0-4, E = S, Se, Te), are discussed, and for a microcrystalline sample of tetrakis(ferrocenylselenolato)stannane, Sn(SeFc)4, the 119Sn and 77Se CP/MAS NMR spectra are reported and compared with the solution spectra.

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