NMR and X-ray Diffraction Study of the Conformational Structure of Poly[N5-(2-hydroxyethyl)-L-glutamine] and Poly[N5-(2-hydroxyethyl)-L-glutamine-co-γ-L-glutamylhydrazide]

1993 ◽  
Vol 58 (10) ◽  
pp. 2415-2427
Author(s):  
Drahomíra Hlavatá ◽  
Hana Pivcová ◽  
Jiří Spěváček ◽  
Dagmar Nosková ◽  
František Rypáček
Keyword(s):  
Solid State ◽  
Benzyl Ester ◽  
Dichloroacetic Acid ◽  
Random Coil ◽  
Conformational Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Nmr Spectrometry ◽  
Cp Mas Nmr

The conformation of poly[N5-(2-hydroxyethyl)L-glutamine] (P(HEG-GH)), in solid state was studied by 13C CP/MAS NMR spectrometry and X-ray diffraction. The association of copolymers in dichloroacetic acid was investigated by following the temperature dependence of their 1H NMR spectra, PHEG and P(HEG-GH) were prepared by the reaction of poly(benzyl γ-L-glutamate) with 2-aminoethanol and 2-aminoethanol-hydrazine mixtures, respectively. The conformation of the copolymers depends on the reaction conditions. While PHEG and the copolymers prepared with the mole ratio of hydrazine to the benzyl ester nH/nB = 0.25 were almost amorphous in solid state and had a random coil conformation and/or randomly oriented helices, at increased concentration of hydrazine (nH/nB = 0.5 and 1.0) P(HEG-GH) formed more or less ordered structure characterized by assemblies of α-helices. The copolymers prepared at nH/nB 3 2.0 showed features of β-sheets. The tendency of the copolymers to form associates in Cl2CHCOOH solutions correlated well with their tendency to form ordered structures in solid state.

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.

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.

Synthesis of Triferrocenylbenzenes by Tantalum(V)-Catalyzed Cyclotrimerization of Ethynylferrocene. The Crystal Structure of 1,3,5-Triferrocenylbenzene

1997 ◽  
Vol 62 (10) ◽  
pp. 1577-1584 ◽  
Author(s):  
Petr Štěpnička ◽  
Ivana Císařová ◽  
Jan Sedláček ◽  
Jiří Vohlídal ◽  
Miroslav Polášek
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Single Crystal ◽  
High Yield ◽  
Isomer Mixture ◽  
State Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Yield Formation

Exclusive, high-yield formation of the cyclotrimers of ethynylferrocene (1) was observed when TaCl5 in benzene was employed as catalyst. Analysis of the resulting isomer mixture by means of HPLC and 1H NMR revealed the presence of 1,3,5-triferrocenylbenzene (sym-2) and 1,2,4-triferrocenylbenzene (asym-2) in the ratio of 4 : 6. A small amount of pure sym-2 isomer was isolated, and its solid-state structure was established by single-crystal X-ray diffraction. The molecules of sym-2 possess a distorted up-up-down arrangement of the ferrocenyl groups attached to the benzene ring.

A bis-Au(III) [28]hexaphyrin triphenylphosphine adduct

2016 ◽  
Vol 20 (08n11) ◽  
pp. 997-1001 ◽  
Author(s):  
Koji Naoda ◽  
Atsuhiro Osuka
Keyword(s):  
Solid State ◽  
Structural Analysis ◽  
Trifluoroacetic Acid ◽  
X Ray Diffraction ◽  
Nmr Spectrum ◽  
X Ray ◽  
H Nmr ◽  
Detailed Structural Analysis ◽  
Nir Absorption ◽  
Plausible Mechanism

Triphenylphosphine was added regioselectively at the C(3) position of bis-Au(III) complex of [26]hexaphyrin 5 in the presence of trifluoroacetic acid to produce [28]hexaphyrin triphenylphosphine adduct 6 in 62% yield, which has been fully characterized by NMR, UV-vis/NIR absorption, and MS spectroscopies, and X-ray diffraction analysis. The rigid planar structure forces 6 to take Hückel antiaromaticity, which has been supported by its 1H NMR spectrum. Curiously, the detailed structural analysis elucidated that the triphenylphosphine moiety exists as a phosphorane form in the solid state. A plausible mechanism via a double protonated 5 is proposed, which can explain the observed regioselectivity.

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.

A solid state NMR and X-ray crystallographic investigation of dynamic disorder in solid tetrahydronaphthalene derivatives

1996 ◽  
Vol 74 (10) ◽  
pp. 1844-1851 ◽  
Author(s):  
Glenn A. Facey ◽  
Terrence J. Connolly ◽  
Corinne Bensimon ◽  
Tony Durst
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
X Ray Diffraction ◽  
Molecular Conformations ◽  
Dynamic Disorder ◽  
X Ray ◽  
H Nmr ◽  
Nmr Data ◽  
Deuterated Analog ◽  
Naphthoic Acid

The solid state disorder of two tetrahydronaphthalene derivatives, N-methyl-N-methoxy-5,6,7,8-tetrahydro-1-naphthamide and 5,6,7,8-tetrahydro-1-naphthoic acid, was studied by solid state NMR and single crystal X-ray diffraction. The X-ray crystal structure of N-methyl-N-methoxy-5,6,7,8-tetrahydro-1-naphthamide was obtained at 123 K. It indicated the presence of two distinct molecular conformations. Solid state 13C CP/MAS NMR data using the dipolar dephasing technique revealed that the two conformations of the molecule are dynamically disordered, while solid state 2H NMR data, collected on a specifically deuterated analog, were used to determine the populations of each conformation as well as an apparent activation energy. Solid state NMR experiments were also used to show that 5,6,7,8-tetrahydro-1-naphthoic acid possesses the same type of dynamic disorder. Key words: deuterium NMR, solid state NMR, dynamic disorder. X-ray, tetrahydronaphthalene derivatives

A new aspect of the “pseudo water” concept of bis(trimethylsilyl)carbodiimide – “pseudohydrates” of aluminum

2018 ◽  
Vol 73 (11) ◽  
pp. 911-918
Author(s):  
Katrin Krupinski ◽  
Erica Brendler ◽  
Robert Gericke ◽  
Jörg Wagler ◽  
Edwin Kroke
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
Quantum Chemical ◽  
Metal Salt ◽  
Similar Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Positional Disorder ◽  
Cp Mas Nmr

AbstractBis(trimethylsilyl)carbodiimide (BTSC), so-called “pseudo water” because of some analogies such as similar (group)electronegativities of Me3Si– vs. H– and –N=C=N– vs. –O–, may form two different kinds of “pseudo hydrates” of metals (M), i.e. M–N(SiMe3)=C=N(SiMe3) and M–N≡C–N(SiMe3)2, derived from its carbodiimide and cyanamide isomeric forms, respectively. With anhydrous AlCl3 in Me3SiCl solution BTSC was shown to be capable of forming both kinds of solvates, i.e. Cl3Al–N(SiMe3)–C≡N(SiMe3) (1) and ((Cl3Al)(Me3Si)NCN)3–Al–(N≡C–N(SiMe3)2)3 (2). Both compounds were isolated as crystalline solids, which undergo condensation reactions upon storage. By single-crystal X-ray diffraction analysis the constitution of 1 was confirmed unambiguously, and quantum chemical calculations (B3LYP/6-311++g(d,p)) confirmed that compound 1 is 6 kcal mol−1 more stable than its hypothetical N,N-bis(trimethylsilyl)cyanamide isomer Cl3Al–N≡C–N(SiMe3)2. Compound 1 represents the first crystallographically confirmed disilylcarbodiimide complex of a metal salt. The molecules of compound 2 are heavily disordered in the solid state (positional disorder of N≡C–N(SiMe3)2 vs. N≡C–N(SiMe3)(AlCl3) and positional disorder of SiMe3 vs. AlCl3 groups in the latter). Therefore, the identity of 2 was additionally confirmed by 13C, 15N, 27Al and 29Si CP/MAS NMR spectroscopy.

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