Chemistry of zwitterionic penta-coordinate silicon compounds of the (ammoniomethyl)bis[glycolato(2–)-O1,O2]silicate type in aqueous and nonaqueous solution

2003 ◽  
Vol 81 (11) ◽  
pp. 1315-1325 ◽  
Author(s):  
Reinhold Tacke ◽  
Rüdiger Bertermann ◽  
Andreas Biller ◽  
Christian Burschka ◽  
Martin Penka
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Computational Chemistry ◽  
Experimental Investigations ◽  
Computational Studies ◽  
X Ray Diffraction ◽  
Model Species ◽  
Silicon Compounds ◽  
X Ray ◽  
H Nmr

The zwitterionic spirocyclic λ5Si-silicates bis[glycolato(2–)-O1,O2][(trimethylammonio)methyl]silicate ([OCH2C(O)O]2SiCH2NMe3, 3) and bis[2-methyllactato(2–)-O1,O2][(trimethylammonio)methyl]silicate ([OCMe2C(O)O]2SiCH2NMe3, 4) were synthesized by treatment of the zwitterionic λ5Si-silicate F4SiCH2NMe3 with 2 mol. equiv. of Me3SiOCR2C(O)OSiMe3 (R = H, Me) (formation of 4 mol. equiv. of Me3SiF). Compounds 3 (isolated as 3•2/3MeCN after drying in vacuo) and 4 were studied by solution 1H, 13C, and 29Si NMR spectroscopy and by solid-state VACP/MAS 13C, 15N, and 29Si NMR experiments, and the solvates 3•MeCN and 4•2MeCN were structurally characterized by single-crystal X-ray diffraction. These experimental investigations were complemented by computational studies of the zwitterions 3 and 4 and the anionic model species bis[2-methyllactato(2–)-O1,O2]hydridosilicate(1–) ([OCMe2C(O)O]2SiH–, 8). Compounds 3•2/3MeCN and 4 and their already known derivatives [OCH2C(O)O]2SiCH2NMe2H (1) and [OCMe2C(O)O]2SiCH2NMe2H (2) were studied for their dynamic behavior (Λ/Δ-enantiomerization) in solution by VT 1H NMR spectroscopy. In addition, compounds 1, 2, 3•2/3MeCN, and 4 were studied in CD3OD and D2O with 1H, 13C, and 29Si NMR experiments.Key words: penta-coordinate silicon, zwitterionic λ5Si-silicates, Λ/Δ-enantiomerism, NMR spectroscopy, computational chemistry.

Sila-Pharmaka, 26. Mitt. [1]. Darstellung und Eigenschaften potentiell curarewirksamer Silicium-Verbindungen, III / Sila-Pharmaca, 26th Communication [1]. Preparation and Properties of Silicon Compounds with Potential Curare-Like Activity, III

1982 ◽  
Vol 37 (11) ◽  
pp. 1461-1471 ◽  
Author(s):  
Reinhold Tacke ◽  
Haryanto Linoh ◽  
Moayad T. Attar-Bashi ◽  
William S. Sheldrick ◽  
Ludger Ernst ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Neuromuscular Blocking ◽  
Neuromuscular Blocking Agents ◽  
X Ray Diffraction ◽  
Silicon Compounds ◽  
X Ray ◽  
Structure Activity Relationships ◽  
H Nmr ◽  
Structure Activity

The potentially curare-like silicon compounds 8a-8f wore synthesized and investigated with respect to their structure-activity relationships. The conformations of the com­pounds in the solid state and in solution were studied by X-ray diffraction analysis (8a-8e) and 1H NMR spectroscopy (8a-8f), respectively. The muscle relaxing properties of 8a-8f were investigated on the mouse. The observed structure-activity relationships are not in accordance with the classical “14 Å model” for neuromuscular blocking agents.

Investigation of the disorder of dibromo- and dichloromethane in their tri-ortho-thymotide clathrates using X-ray diffraction and solid-state 2H NMR spectroscopy

2011 ◽  
Vol 89 (7) ◽  
pp. 854-862
Author(s):  
Glenn A. Facey ◽  
Ilia Korobkov
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Guest Molecule ◽  
Type B ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Twofold Axis ◽  
H Nmr ◽  
Heavy Atoms

The tri-ortho-thymotide (TOT) clathrates of dibromo- and dichloromethane were characterized by single crystal X-ray diffraction at 200 K and solid-state 2H NMR spectroscopy as a function of temperature. The host structure was found to be typical of other cage-type TOT clathrates. The X-ray results showed a substantial amount of disorder among the guest molecules. In both clathrates, multiple guest molecule positions could be modeled. The heavy atoms of all the guest molecule positions lie approximately in the same plane, with some out-of-plane distortion. The guest molecules were of two different types in positions symmetric about the crystallographic twofold rotation axis: type A guests, with carbon atoms well removed from the crystallographic twofold axis, and type B guests, with carbon atoms very close to the twofold axis. The 2H NMR spectra for the guests confirmed that the disorder was dynamic. The experimental results could be accounted for by the presence of three simultaneous types of molecular motion, all fast with respect to the 2H quadrupolar interaction: (i) twofold molecular flips about the molecular C2 symmetry axis, (ii) exchange between the type A and type B sites in a single plane, and (iii) a two-site libration of the plane containing the heavy atoms of the A and B guest sites with a temperature-dependent amplitude.

scholarly journals Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies

2018 ◽  
Vol 14 ◽  
pp. 1723-1733 ◽  
Author(s):  
Rakesh Puttreddy ◽  
Ngong Kodiah Beyeh ◽  
S Maryamdokht Taimoory ◽  
Daniel Meister ◽  
John F Trant ◽  
...  
Keyword(s):  
Solid State ◽  
Conformational Changes ◽  
Form Solution ◽  
Solution Phase ◽  
Computational Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Additional Stability ◽  
Electron Donating Groups

Host–guest complexes of C-hexyl-2-bromoresorcinarene (BrC6) with twelve potential aromatic N-oxide guests were studied using single crystal X-ray diffraction analysis and 1H NMR spectroscopy. In the solid state, of the nine obtained X-ray crystal structures, eight were consistent with the formation of BrC6-N-oxide endo complexes. The lone exception was from the association between 4-phenylpyridine N-oxide and BrC6, in that case the host forms a self-inclusion complex. BrC6, as opposed to more rigid previously studied C-ethyl-2-bromoresorcinarene and C-propyl-2-bromoresorcinarene, undergoes remarkable cavity conformational changes to host different N-oxide guests through C–H···π(host) interactions. In solution phase CD3OD/CDCl3 (1:1 v/v), all twelve N-oxide guests form endo complexes according to 1H NMR; however, in more polar CD3OD/DMSO-d 6 (9:1 v/v), only three N-oxides with electron-donating groups form solution-phase endo complexes with BrC6. In solid-state studies, 3-methylpyridine N-oxide+BrC6 crystallises with both the upper- and lower-rim BrC6 cavities occupied by N-oxide guests. Computational DFT-based studies support that lower-rim long hexyl chains provide the additional stability required for this ditopic behaviour. The lower-rim cavity, far from being a neutral hydrophobic environment, is a highly polarizable electrostatically positive surface, aiding in the binding of polar guests such as N-oxides.

scholarly journals Tautomerisation in 1-(4-Methylphenylazo)naphthalen-2-ol and 2-(4-Methylphenylazo)-4-methylphenol: A Crystallographic and 13C{1H}NMR Study

1999 ◽  
Vol 23 (3) ◽  
pp. 178-179
Author(s):  
Wendy I. Cross ◽  
Kevin R. Flower ◽  
Robin G. Pritchard
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Resonant Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Nmr Study ◽  
Acetic Acid Esters ◽  
Acid Esters ◽  
Equivalent Carbon

The acetic acid esters of 1-(4-methylphenylazo)naphthalen-2-ol 1 and 2-(4-methylphenylazo)-4-methylphenol 3 are prepared and characterised by single crystal X-ray diffraction studies and 13C{1H}NMR spectroscopy; the position of the C(2)13C resonance for the ester is used to predict the position of resonant frequency of the equivalent carbon in the parent alcohols and hence, calculate the position of the azo-hydrazone equilibrium in these compounds.

scholarly journals Synthesis, Structure, and Properties of a Dinuclear Cu(II) Coordination Polymer Based on Quinoxaline and 3,3-Thiodipropionic Acid Ligands

2021 ◽  
Author(s):  
Adedibu Clement Tella ◽  
Samson Owalude ◽  
Vincent Adimula ◽  
Adetola Oladipo ◽  
Victoria Olayemi ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Nitrogen Atom ◽  
Coordination Polymer ◽  
Elemental Analysis ◽  
Catalytic Reduction ◽  
Copper Acetate ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr

Abstract The coordination polymer [Cu2(TDPH)4(QNX)].DMF, (QNX = Quinoxaline; TDPH = 3,3-thiodipropionic acid), has been prepared by reaction of copper acetate, TDPH, and quinoxaline. The compound was characterized by elemental analysis, FTIR spectroscopy, and single-crystal X-ray diffraction. The crystal is monoclinic with a P21/n space group and dimensions of a = 12.889(3) Å, b = 14.983(4) Å, c = 14.091(3) Å, α = 90 °, β = 90.200(11) °, γ = 90 °, V = 2721.18 (2) Å3, Z = 4. The ligands are hexagonally coordinated to the Cu(II) centre in the form of Cu2O4N with one nitrogen atom from the quinoxaline ligand, and four oxygen atoms from four TDPH molecules in a monodentate fashion. The Cu-Cu bond length was 2.642(1) and 2.629(1) Å for the Cu1----Cu1 and Cu2----Cu2 bonds. The QNX ligand bridged the two copper atoms. The catalytic reduction of 4-nitrophenol to 4-aminophenol using NaBH4 in the presence of [Cu2(TDPH)4(QNX)].DMF, as catalyst was completed within 11 minutes. The 4-aminophenol product was confirmed using 1H NMR spectroscopy.

Imidazole-containing Bispidine Ligands: Synthesis, Structure and Cu(II) Complexation

2011 ◽  
Vol 66 (7) ◽  
pp. 721-728 ◽  
Author(s):  
Martin Walther ◽  
Madlen Matterna ◽  
Stefanie Juran ◽  
Silke Fähnemann ◽  
Holger Stephan ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Enol Form ◽  
Trans Configuration ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Impact ◽  
Configurational Isomerism

The preparation and characterization of tris-pyridyl bispidine (3,7-diazabicyclo[3.3.1]nonane) derivatives with benzimidazole and imidazole donor groups at the N-3 position of the bispidine skeleton and their copper(II) complexes are reported. The impact of the hetaryl substituents on the configurational isomerism of piperidones and their corresponding bispidones has been studied by NMR spectroscopy, revealing the exclusive appearance in the enol form for the piperidones in solution and the trans-configuration regarding the two pyridyl substituents, as well as the sole formation of the unsymmetric exo-endo isomers for the corresponding bispidones. Thus, the bispidones are preorganized ligands for building pentacoordinated complexes, confirmed by the preparation and characterization of the corresponding Cu(II) complexes. Of the di-pyridyl piperidones with benzimidazole and imidazole substituents, and of the Cu(II) complex of the benzimidazole-containing bispidone, crystals have become available for the analysis by X-ray diffraction, showing that the piperidones form the enol tautomers also in the solid state.

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