Spectroscopic conformational study of PMS 952, a specific imidazoline ligand. Experimental results

1999 ◽  
Vol 77 (12) ◽  
pp. 2015-2024 ◽  
Author(s):  
Marie-Hélène Baron ◽  
Sabine Halut-Desportes ◽  
Hai-Fen Ye ◽  
Jack Huet ◽  
Edith Favre
Keyword(s):  
Hydrogen Bonds ◽  
Tautomeric Form ◽  
Proton Donor ◽  
Coupling Constants ◽  
X Ray ◽  
H Nmr ◽  
Ftir Studies ◽  
Nmr Study ◽  
Imidazoline Ring ◽  
Imidazoline Derivative

X-ray analysis of PMS 952 displays two kinds of very strong hydrogen bonds, an intramolecular one stabilizing the conformer A and an intermolecular one that associates conformers A to form two infinite chains. The 1H NMR study of vicinal coupling constants based on dihedral angle values, evidences that PMS 952 takes up an eclipsed conformation, in CCl4 and CDCl3 solutions, closely related to the conformation in solid state. Deuterium exchange in methanol-d4 points out the presence of a tautomeric form. However, as there is spectral evidence neither from NMR nor from FTIR studies for such a tautomer, this specie cannot be taken into account to explain the complexity of the FTIR spectra. NMR data also reveal that the imidazoline ring freely rotates while FTIR analysis allows characterizing two conformers (A and B), with lifetime shorter than NMR time scale. These two conformers are stabilized by two different intramolecular H-bonds. Taking into account that conformer A could exist in two states (monomer A and (A)n-chains), an equilibrium between A, (A)n, and B entities allowed the assignment of all main bands of the IR spectra, assigned to vNH, vOH, vCH, and vCN modes. The strength of hydrogen bonds is solvent dependent. Polar solvents, either proton donor or acceptor stabilized the conformer A, while CCl4 favors the conformer B.Key words: hydrogen bonds, X-ray, NMR, FTIR, imidazoline derivative.

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.

Preliminary Results of a 20 K X-Ray Study of Citrinin

1993 ◽  
Vol 48 (1-2) ◽  
pp. 99-104 ◽  
Author(s):  
R. Destro ◽  
F. Merati
Keyword(s):  
Dipole Moment ◽  
Hydrogen Bonds ◽  
Charge Density ◽  
Topological Analysis ◽  
Coupling Constants ◽  
Molecular Dipole ◽  
X Ray ◽  
A Value ◽  
Quadrupole Coupling ◽  
Asymmetry Parameters

Abstract A total of about 37 000 diffracted intensities has been measured at 20 K for a spherical single crystal of citrinin. Using a multipole formalism to interpret the X-ray data, maps of the charge density and of its Laplacian, as well as for the electrostatic potential have been derived. A value of 7(2) D has been obtained for the magnitude of the molecular dipole moment. A study of the electric field gradient (EFG) at the nuclei has yielded the atomic quadrupole coupling constants (QCC) and asymmetry parameters (η). A topological analysis of the charge density has been performed to characterize the intramolecular covalent and hydrogen bonds.

1H NMR study of the solvolysis of the paramagnetic tetrachloro-bis(imidazole)ruthenium(III) anion in water, methanol, and dimethyl sulfoxide

1995 ◽  
Vol 73 (4) ◽  
pp. 471-482 ◽  
Author(s):  
Craig Anderson ◽  
André L. Beauchamp
Keyword(s):  
Dimethyl Sulfoxide ◽  
1H Nmr ◽  
Room Temperature ◽  
Single Species ◽  
X Ray Diffraction ◽  
Chloro Complexes ◽  
X Ray ◽  
H Nmr ◽  
Nmr Study ◽  
Nmr Signals

The 1H NMR signals of the Ru(III) species present in solution are considerably broadened and shifted by paramagnetism, but they can be used to follow chloride displacement in the trans-[RuCl4Im2]− ion. This anion remains predominant for several hours at room temperature in D2O, but its signals are progressively replaced by those of a monoaqua [RuCl3(D2O)Im2] complex. Over a period of days, two new sets of peaks appear, corresponding to two isomers of [RuCl2(D2O)2Im2]+. The same behaviour is observed for the 1-methyl-and 4-methylimidazole analogues. These reactions can be driven backwards by addition of KCl, but [RuCl4Im2]− is not quantitatively regenerated in solution even for 6 M NaCl. Within several months, the [RuCl2(D2O)2Im2]+ isomers further aquate to a single species [RuCl(D2O)3Im2]2+. In CD3OD, displacement of the first chloride of [RuCl4Im2]− takes place faster, over several hours, but substitution stops at the [RuCl3(CD3OD)Im2] stage. In DMSO, substitution occurs very slowly. The [RuCl3(DMSO)Im2]:[RuCl4Im2]−mixture (1:2) obtained after 12 days starts to show very slow reduction to two Ru(II) species, one of which precipitates as yellow crystals. From X-ray diffraction work (monoclinic, P21/n, a = 9.951, b = 8.564, c = 10.527 Å, β = 92.95°, R = 0.033), the compound was identified as [RuCl2(DMSO-d6)2Im2], where the metal has a trans-trans-trans coordination and the DMSO ligands are S-bonded. Keywords: paramagnetic ruthenium anion, solvolysis, chloro complexes.

Preparation and Crystal Structure of Genistein Benzenesulfonate Prodrugs

2008 ◽  
Vol 2008 (10) ◽  
pp. 555-558 ◽  
Author(s):  
You Peng ◽  
Zeyuan Deng ◽  
Shaojie Lang ◽  
Yawei Fan
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Sulfonic Acid ◽  
Nmr Spectra ◽  
High Yield ◽  
X Ray Diffraction ◽  
Aromatic Rings ◽  
X Ray ◽  
H Nmr ◽  
Ester Prodrugs

In order to improve bioavailability and anticancer activity of genistein, a series of novel sulfonic acid ester prodrugs of the isoflavone genistein were synthesised in high yield with excellent regioselectivity. Their structures were characterised by IR, MS, elemental analysis and 1H NMR spectra. The crystal structure was examined by X-ray diffraction. X-ray structure determination revealed that all the aromatic rings in the compound are not coplanar. In the crystal structure, molecules are linked through intermolecular C-H···O hydrogen bonds, forming layers parallel to the ab plane.

(3E)-5-Hydroxy-3-[5-(hydroxymethyl)furan-2-ylmethylene]-1-benzofuran-2(3H)-one

2007 ◽  
Vol 63 (11) ◽  
pp. o4354-o4354
Author(s):  
Hong-Yan Ma ◽  
Ji Shi ◽  
Chang-Hong Wang ◽  
Zheng-Tao Wang
Keyword(s):  
Hydrogen Bonds ◽  
Spectroscopic Data ◽  
Furan Ring ◽  
Crystallographic Analysis ◽  
Relative Configuration ◽  
X Ray ◽  
H Nmr ◽  
Compound C ◽  
A Chain ◽  
C Nmr

The title compound, C14H10O5, was isolated from Senecio cannabifolius Less var. integrifolius aqueous extract. The structure was elucidated on the basis of spectroscopic data, including MS, 1H NMR and 13C NMR, and the relative configuration was confirmed by X-ray crystallographic analysis. The benzofuran ring is almost coplanar with the furan ring [dihedral angle = 10.47 (15)°]. A chain is formed through supramolecular R 2 2(10) synthons and three-centre hydrogen bonds.

Tizanidine and tizanidine hydrochloride: on the correct tautomeric form of tizanidine

2011 ◽  
Vol 68 (1) ◽  
pp. o28-o32 ◽  
Author(s):  
Sándor L. Bekö ◽  
Silke D. Thoms ◽  
Martin U. Schmidt ◽  
Michael Bolte
Keyword(s):  
Hydrogen Bonds ◽  
Structure Determination ◽  
Tautomeric Form ◽  
Asymmetric Unit ◽  
Free Base ◽  
Adrenergic Agonist ◽  
Acta Cryst ◽  
Hydrochloride Salt ◽  
H Nmr

A crystallization series of tizanidine hydrochloride, used as a muscle relaxant for spasticity acting centrally as an α2-adrenergic agonist, yielded single crystals of the free base and the hydrochloride salt. The crystal structures of tizanidine [systematic name: 5-chloro-N-(imidazolidin-2-ylidene)-2,1,3-benzothiadiazol-4-amine], C9H8ClN5S, (I), and tizanidine hydrochloride {systematic name: 2-[(5-chloro-2,1,3-benzothiadiazol-4-yl)amino]imidazolidinium chloride}, C9H9ClN5S+·Cl−, (II), have been determined. Tizanidine crystallizes with two almost identical molecules in the asymmetric unit (r.m.s. deviation = 0.179 Å for all non-H atoms). The molecules are connected by N—H...N hydrogen bonds forming chains running along [2\overline{1}1]. The present structure determination corrects the structure determination of tizanidine by Johnet al.[Acta Cryst.(2011), E67, o838–o839], which shows an incorrect tautomeric form. Tizanidine does not crystallize as the usually drawn 2-amino–imidazoline tautomer, but as the 2-imino–imidazolidine tautomer. This tautomer is present in solution as well, as shown by1H NMR analysis. In tizanidine hydrochloride, cations and anions are connected by N—H...Cl hydrogen bonds to form layers parallel to (100).

Synthesis and X-Ray Crystal Structure of Two Novel Ester Ferrocenophanes

2007 ◽  
Vol 62 (4) ◽  
pp. 605-609 ◽  
Author(s):  
Li Tao ◽  
Yang Bingqin ◽  
Gao Bo
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Elemental Analysis ◽  
3D Structure ◽  
Spectroscopic Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Carbonyl Chloride ◽  
Tof Ms

Two novel ester ferrocenophanes have been prepared by esterification of 1,1′-ferrocenedi(carbonyl chloride) with glycol and 1,4-butanediol, respectively. Both of them have been characterized by IR, elemental analysis, MALDI-TOF MS and 1H NMR spectroscopic methods, and their structures have been elucidated by X-ray diffraction. The intermolecular associations based on C-H···O hydrogen bonds have also been discussed. These molecules are assembled into chains, and the chains are further assembled into a 3D structure through several hydrogen bonds.

Structure and Dynamics of Crystal Solvates Hexaphenylditin • 2X, X=Benzene , Toluene, Fluorobenzene , Chlorobenzene , and Aniline. An X-Ray, P(VAPOR)=ƒ(T)> and 2H NMR Study

1995 ◽  
Vol 50 (8) ◽  
pp. 758-769
Author(s):  
Karin Eckardt ◽  
Hartmut Fuess ◽  
Masakazu Hattori ◽  
Ryuichi Ikeda ◽  
Hiroshi Ohki ◽  
...  
Keyword(s):  
Benzene Molecule ◽  
Threefold Axis ◽  
X Ray ◽  
Lattice Constants ◽  
H Nmr ◽  
Structure And Dynamics ◽  
Nmr Study ◽  
Benzene Toluene ◽  
Vapor Pressure Measurements

Abstract The crystal structures of the hexaphenylditin (hpdt) solvate compounds, (C6H5)3Sn-Sn (C6H5)3 • 2X, solvent X = aniline (an), chlorobenzene (cb), fluorobenzene (fb), and toluene (to), were determined. They are isomorphous with the known benzene (be) crystal solvate compound hpdt • 2be, crystallizing in the trigonal space group R3̅, with Z=3 formula units per unit cell. The lattice constants (in pm), from X-ray powder diffraction, are: hpdt • 2an (1): a= 1170.01 (9), c = 2641.49 (20), c/a = 2.2577; hpdt • 2be (2): a = 1165.45 (5), c = 2641.30 (9), c/a = 2.2663; hpdt • 2cb (3): 0=1175.88(5), c = 2661.66(10), c/a = 2.2635; hpdt • 2fb (4): 0 = 1167.69(5), c = 2643.21 (9), c/a = 2.2636; hpdt • 2to (5): a=1182.24 (7), c = 2649.13(11), c/a = 2.2408. The single crystal structure determination of 5 leads to a = 1180.2(2), c = 2651.4 (5). The decomposition of 5 results in the monoclinic phase of hexaphenylditin. Vapor pressure measurements p=ƒ(T), 260 <̲ T/K <̲350, of the compounds have been performed and the heats of vaporization ΔHv/kJmole-1 were determined: 52.44 (1), 46.65 (2), 34.52 (3), 43.08 (4), 55.30 (5). The dynamics of the host molecules C6D6, C6D5CD3 and C6H5ND2 were studied by 2H NMR in the range 295 <̲ T/K <̲ 118. The rotation of the benzene molecule about its threefold axis is maintained till 118 K; in the case of toluene the rotation of the phenyl ring about the pseudo-threefold axis freezes in below 180 K, while the methyl group still rotates about its threefold axis till 123 K.

A novel tubular hydrogen-bond pattern in a new diazaphosphole oxide: a combination of X-ray crystallography and theoretical study of hydrogen bonds

2017 ◽  
Vol 73 (7) ◽  
pp. 508-516 ◽  
Author(s):  
Fahimeh Sabbaghi ◽  
Mehrdad Pourayoubi ◽  
Abolghasem Farhadipour ◽  
Nazila Ghorbanian ◽  
Pavel V. Andreev
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Coupling Constant ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Hydrogen Bond Pattern ◽  
Orbital Analysis ◽  
Tubular Array ◽  
Hydrogen Bonded

In the structure of 2-(4-chloroanilino)-1,3,2λ4-diazaphosphol-2-one, C12H11ClN3OP, each molecule is connected with four neighbouring molecules through (N—H)2...O hydrogen bonds. These hydrogen bonds form a tubular arrangement along the [001] direction built from R 3 3(12) and R 4 3(14) hydrogen-bond ring motifs, combined with a C(4) chain motif. The hole constructed in the tubular architecture includes a 12-atom arrangement (three P, three N, three O and three H atoms) belonging to three adjacent molecules hydrogen bonded to each other. One of the N—H groups of the diazaphosphole ring, not co-operating in classical hydrogen bonding, takes part in an N—H...π interaction. This interaction occurs within the tubular array and does not change the dimension of the hydrogen-bond pattern. The energies of the N—H...O and N—H...π hydrogen bonds were studied by NBO (natural bond orbital) analysis, using the experimental hydrogen-bonded cluster of molecules as the input file for the chemical calculations. In the 1H NMR experiment, the nitrogen-bound proton of the diazaphosphole ring has a high value of 17.2 Hz for the 2 J H–P coupling constant.

Refinement of labile hydrogen positions based on DFT calculations of 1H NMR chemical shifts: comparison with X-ray and neutron diffraction methods

2017 ◽  
Vol 15 (21) ◽  
pp. 4655-4666 ◽  
Author(s):  
Michael G. Siskos ◽  
M. Iqbal Choudhary ◽  
Ioannis P. Gerothanassis
Keyword(s):  
High Resolution ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Dft Calculations ◽  
Energy Minimization ◽  
Chemical Shifts ◽  
Labile Hydrogen ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
H Nmr

High resolution structures of hydrogen bonds: experimental (δexp) and GIAO calculated 1H NMR chemical shifts, δcalc, in combination with DFT energy minimization, are an excellent means for obtaining high resolution structures of labile protons.

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