scholarly journals 1H,13C, and15N NMR Studies of Au(III) and Pd(II) Chloride Complexes and Organometallics with 2-Acetylpyridine and 2-Benzoylpyridine

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Daria Niedzielska ◽  
Tomasz Pawlak ◽  
Tomasz Czubachowski ◽  
Leszek Pazderski
Keyword(s):  
Chemical Shifts ◽  
Molecular Structures ◽  
Nmr Studies ◽  
Chloride Complexes ◽  
Coordination Modes ◽  
Nuclear Shielding

Au(III) and Pd(II) chloride complexes with N(1),O-chelating 2-acetylpyridine (2apy) and N(1)- monodentately binding 2-benzoylpyridine (2bz′py)-[Pd(2apy)Cl2], [Au(2bz′py)Cl3],trans-[Pd(2bz′py)2Cl2], as well as Au(III) chloride organometallics with monoanionic forms of 2apy or 2bz′py, deprotonated at the acetyl or benzyl side groups (2apy*, 2bz′py*)-[Au(2apy*)Cl2], [Au(2bz′py*)Cl2], were studied by1H,13C, and15N NMR.1H,13C, and15N coordination shifts (i.e., differences between the respective , , and chemical shifts of the same atom in the complex and ligand molecules: , , ) were discussed in relation to the molecular structures and coordination modes, as well as to the factors potentially influencing nuclear shielding. Analogous NMR measurements were performed for the new (2bz′pyH)[AuCl4] salt.

14N-NMR-Untersuchungen an Aminophosphinen / 14N NMR Studies on Aminophosphines

1978 ◽  
Vol 33 (5) ◽  
pp. 515-520 ◽  
Author(s):  
K. Barlos ◽  
H. Nöth ◽  
B. Wrackmeyer
Keyword(s):  
Chemical Shifts ◽  
Steric Effects ◽  
Nmr Studies ◽  
Π Interactions ◽  
Nuclear Shielding ◽  
14N Nmr

Abstract14N chemical shifts of a series of cyclic and noncyclic aminophosphines are reported. The nuclear shielding of nitrogen decreases with increasing number of halogen substituents at phosphorus as well as with increasing number of phosphinyl groups attached to nitrogen. In addition to the influence of electronegativity PN(π)-interactions may account for the observed shielding. Steric effects are discussed.

scholarly journals Resolving Entangled JH-H-Coupling Patterns for Steroidal Structure Determinations by NMR Spectroscopy

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2643
Author(s):  
Danni Wu ◽  
Kathleen Joyce Carillo ◽  
Jiun-Jie Shie ◽  
Steve S.-F. Yu ◽  
Der-Lii M. Tzou
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr Spectroscopy ◽  
Chemical Shifts ◽  
Atomic Level ◽  
Molecular Structures ◽  
Naturally Occurring ◽  
Structure Determinations ◽  
Ligand Interactions ◽  
Synthetic Steroids ◽  
The Individual

For decades, high-resolution 1H NMR spectroscopy has been routinely utilized to analyze both naturally occurring steroid hormones and synthetic steroids, which play important roles in regulating physiological functions in humans. Because the 1H signals are inevitably superimposed and entangled with various JH–H splitting patterns, such that the individual 1H chemical shift and associated JH–H coupling identities are hardly resolved. Given this, applications of thess information for elucidating steroidal molecular structures and steroid/ligand interactions at the atomic level were largely restricted. To overcome, we devoted to unraveling the entangled JH–H splitting patterns of two similar steroidal compounds having fully unsaturated protons, i.e., androstanolone and epiandrosterone (denoted as 1 and 2, respectively), in which only hydroxyl and ketone substituents attached to C3 and C17 were interchanged. Here we demonstrated that the JH–H values deduced from 1 and 2 are universal and applicable to other steroids, such as testosterone, 3β, 21-dihydroxygregna-5-en-20-one, prednisolone, and estradiol. On the other hand, the 1H chemical shifts may deviate substantially from sample to sample. In this communication, we propose a simple but novel scheme for resolving the complicate JH–H splitting patterns and 1H chemical shifts, aiming for steroidal structure determinations.

Synthesis and characterization of 19F NMR chelators for measurement of cytosolic free Ca

1987 ◽  
Vol 252 (4) ◽  
pp. C441-C449 ◽  
Author(s):  
L. A. Levy ◽  
E. Murphy ◽  
R. E. London
Keyword(s):  
Chemical Shifts ◽  
Cell Types ◽  
Free Calcium ◽  
Tetraacetic Acid ◽  
Nmr Studies ◽  
Cytosolic Free Calcium ◽  
Fluorine Nmr ◽  
Dissociation Constant Kd

Fluorine 19 nuclear magnetic resonance (NMR) studies of intracellular fluorinated calcium chelators provide a useful strategy for the determination of cytosolic free calcium levels in cells and perfused organs. However, the fluorinated chelator with the highest affinity for calcium ions which has been described to date. 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), exhibits a dissociation constant (Kd) value 5- to 10-fold greater than the intracellular calcium concentration levels in most cell types, thus limiting the ability of fluorine NMR to report these concentrations reliably. We have consequently designed and synthesized several fluorinated calcium chelators with higher affinity for calcium. The best of these, 2-(2-amino-4-methyl-5-fluorophenoxy)-methyl-8 aminoquinidine-N,N,N',N'-tetraacetic acid (quinMF), has a Kd value approximately 10 times lower than that of 5FBAPTA. Several of the newly synthesized indicators have different chemical shifts for the calcium complexed and uncomplexed chelators to allow the simultaneous use of two indicators. In addition to providing information about the level of cytosolic free calcium, chelators containing a quinoline ring exhibit considerable sensitivity to magnesium levels and hence have potential application for the determination of cytosolic-magnesium concentrations. Application of these chelators is illustrated by determination of the cytosolic-free calcium level in erythrocytes. Use of quinMF, the chelator with the lowest Kd value, gives a calcium value of 25-30 nM.

NMR studies of tandem WW domains of Nedd4 in complex with a PY motif-containing region of the epithelial sodium channel

1998 ◽  
Vol 76 (2-3) ◽  
pp. 341-350 ◽  
Author(s):  
Voula Kanelis ◽  
Neil A Farrow ◽  
Lewis E Kay ◽  
Daniela Rotin ◽  
Julie D Forman-Kay
Keyword(s):  
Chemical Shift ◽  
Sodium Channel ◽  
Chemical Shifts ◽  
Epithelial Sodium Channel ◽  
Chemical Shift Assignment ◽  
Nmr Studies ◽  
Ww Domains ◽  
Ww Ii ◽  
Py Motif ◽  
Shift Assignment

Nedd4 (neuronal precursor cell-expressed developmentally down-regulated 4) is a ubiquitin-protein ligase containing multiple WW domains. We have previously demonstrated the association between the WW domains of Nedd4 and PPxY (PY) motifs of the epithelial sodium channel (ENaC). In this paper, we report the assignment of backbone 1Hα, 1HN, 15N, 13C', 13Cα, and aliphatic 13C resonances of a fragment of rat Nedd4 (rNedd4) containing the two C-terminal WW domains, WW(II+III), complexed to a PY motif-containing peptide derived from the β subunit of rat ENaC, the βP2 peptide. The secondary structures of these two WW domains, determined from chemical shifts of 13Cα and 13Cβ resonances, are virtually identical to those of the WW domains of the Yes-associated protein YAP65 and the peptidyl-prolyl isomerase Pin1. Triple resonance experiments that detect the 1Hα chemical shift were necessary to complete the chemical shift assignment, owing to the large number of proline residues in this fragment of rNedd4. A new experiment, which correlates sequential residues via their 15N nuclei and also detects 1Hα chemical shifts, is introduced and its utility for the chemical shift assignment of sequential proline residues is discussed. Data collected on the WW(II+III)-βP2 complex indicate that these WW domains have different affinities for the βP2 peptide.Key words: WW domain, PY motif, Nedd4, ENaC, NMR.

scholarly journals NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

2011 ◽  
Vol 7 ◽  
pp. 1205-1214 ◽  
Author(s):  
Damjan Makuc ◽  
Jennifer R Hiscock ◽  
Mark E Light ◽  
Philip A Gale ◽  
Janez Plavec
Keyword(s):  
Conformational Changes ◽  
Chemical Shifts ◽  
Dihydrogen Phosphate ◽  
Nmr Studies ◽  
Receptor Complexes ◽  
Hydrogen Bond Interactions ◽  
Weak Binding ◽  
Oxo Anions ◽  
Induced Changes ◽  
Good Agreement

The conformational properties of 1,3-diindolylureas and thioureas were studied by a combination of heteronuclear NMR spectroscopy and quantum mechanics calculations. NOE experiments showed that the anti–anti conformer along the C7–N7α bonds was predominant in DMSO-d 6 solution in the absence of anions. Anion-induced changes in the 1H and 15N chemical shifts confirm the weak binding of chloride anions with negligible conformational changes. Strong deshielding of ureido protons and moderate deshielding of indole NH was observed upon the addition of acetate, benzoate, bicarbonate and dihydrogen phosphate, which indicated that the predominant hydrogen bond interactions occurred at the urea donor groups. Binding of oxo-anions caused conformational changes along the C7–N7α bonds and the syn–syn conformer was preferred for anion–receptor complexes. The conformational changes upon anion binding are in good agreement with energetic preferences established by ab initio calculations.

scholarly journals Silylated gallium and indium chalcogenide ring systems as potential precursors to ME (E=O, S) materials

2013 ◽  
Vol 11 (7) ◽  
pp. 1225-1238
Author(s):  
Iliana Medina-Ramírez ◽  
Cynthia Floyd ◽  
Joel Mague ◽  
Mark Fink
Keyword(s):  
Thermal Decomposition ◽  
Room Temperature ◽  
Membered Ring ◽  
Molecular Structures ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
High Yields ◽  
Vt Nmr ◽  
State 1

AbstractThe reaction of R3M (M=Ga, In) with HESiR′3 (E=O, S; R′3=Ph3, iPr3, Et3, tBuMe2) leads to the formation of (Me2GaOSiPh3)2(1); (Me2GaOSitBuMe2)2(2); (Me2GaOSiEt3)2(3); (Me2InOSiPh3)2(4); (Me2InOSitBuMe2)2(5); (Me2InOSiEt3)2(6); (Me2GaSSiPh3)2(7); (Et2GaSSiPh3)2(8); (Me2GaSSiiPr3)2(9); (Et2GaSSiiPr3)2(10); (Me2InSSiPh3)3(11); (Me2InSSiiPr3)n(12), in high yields at room temperature. The compounds have been characterized by multinuclear NMR and in most cases by X-ray crystallography. The molecular structures of (1), (4), (7) and (8) have been determined. Compounds (3), (6) and (10) are liquids at room temperature. In the solid state, (1), (4), (7) and (9) are dimers with central core of the dimer being composed of a M2E2 four-membered ring. VT-NMR studies of (7) show facile redistribution between four- and six-membered rings in solution. The thermal decomposition of (1)–(12) was examined by TGA and range from 200 to 350°C. Bulk pyrolysis of (1) and (2) led to the formation of Ga2O3; (4) and (5) In metal; (7)–(10) GaS and (11)–(12) InS powders, respectively.

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