A Series of Diamagnetic Pyridine Monoimine Rhenium Complexes with Different Degrees of Metal-to-Ligand Charge Transfer: Correlating 13 C NMR Chemical Shifts with Bond Lengths in Redox-Active Ligands

2016 ◽  
Vol 22 (30) ◽  
pp. 10638-10650 ◽  
Author(s):  
Daniel Sieh ◽  
Clifford P. Kubiak
Keyword(s):  
Charge Transfer ◽  
Chemical Shifts ◽  
Rhenium Complexes ◽  
Redox Active Ligands ◽  
Nmr Chemical Shifts ◽  
Bond Lengths ◽  
Redox Active ◽  
Ligand Charge Transfer ◽  
C Nmr

Correlations between carbon-13 nuclear magnetic resonance and X-ray crystallography for pyrroles containing electron-withdrawing groups

1985 ◽  
Vol 63 (10) ◽  
pp. 2683-2690 ◽  
Author(s):  
J. B. Paine III ◽  
D. Dolphin ◽  
J. Trotter ◽  
T. J. Greenhough
Keyword(s):  
Chemical Shifts ◽  
Direct Methods ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
Competitive Effects ◽  
Bond Lengths ◽  
X Ray Crystallography ◽  
Phenyl Rings ◽  
Crystallographic Structures ◽  
C Nmr

The 13C nmr chemical shifts of benzyl 4-ethyl-3,5-dimethylpyrrole-2-carboxylate (1), methyl E-3-(3-ethyl-4,5-dimethylpyrrol-2-yl)-2-cyanopropenoate (2), and methyl E-3-(5-(benzyloxy)carbonyl-3-ethyl-4-methylpyrrol-2-yl)-2-cyanopropenoate (3) have been compared to their X-ray crystallographic structures. The 13C nmr chemical shifts were determined by direct comparison of a series of closely related homologs.Crystal data for 1, 2, and 3 are as follows: 1, monoclinic, P21/c, a = 14.934(2), b = 6.674(2), c = 15.269(2) Å, β = 101.96(1)°, Z = 4; 2, monoclinic, P21/n, a = 7.3030(3), b = 13.478(1), c = 12.985(1) Å, β = 97.48(1)°, Z = 4; 3, monoclinic, P21/c, a = 11.157(2), b = 13.109(2), c = 14.068(1) Å, β = 115.47(1)°, Z = 4. The structures were determined with diffractometer data by direct methods, and refined by full-matrix least-squares techniques to R = 0.052, 0.040, 0.038 for 862, 2032, 1483 reflexions, respectively. The molecules are approximately planar, except for deviations of the phenyl rings and of the terminal carbon atoms of the C3-ethyl groups from the molecular planes. The bond lengths in the pyrrole rings differ from those in pyrrole itself, as a result of the presence of the strongly electron-withdrawing sustituents; exocyclic bond lengths also exhibit differences from normal values.The competitive effects of the various electron withdrawing groups have been correlated to change in bond lengths, 13C chemical shifts, and the chemical reactions of the pyrrolic nucleus.

Synthesis, Characterization and Photophysical Properties of Rhenium(I) Complexes Containing 4,5-Diazafluorene Ligan

2011 ◽  
Vol 239-242 ◽  
pp. 2612-2615
Author(s):  
Jie Xiu Wang ◽  
Feng Zhao
Keyword(s):  
Charge Transfer ◽  
Fluorescence Spectra ◽  
Photophysical Properties ◽  
Absorption And Fluorescence Spectra ◽  
Rhenium Complexes ◽  
H Nmr ◽  
Ligand Charge Transfer

Two related tricarbonyl rhenium complexes with the formula of [Re(CO)3(L)Cl], where L=4,5-diazafluoren-9-one (Dafo-Re) and 9-(phenylamino)-4,5-diazafluoren (PADF-Re) were successfully synthesized with the aim to explore the effect of the geometry of Dafo on Rhenium(I) coordination, and characterized by1H NMR. Photophysical behaviors are investigated by UV–vis absorption and Fluorescence spectra. The two complexes Dafo-Re and PADF-Re show metal-to-ligand charge transfer absorptions at ca.391nm, ca.394 nm and emissions at ca.492nm, ca.470nm, respectively.

Synthesis, X-ray structure determination, and formation of 3,4,5-trichloroguaiacol occurring in kraft pulp spent bleach liquors

1980 ◽  
Vol 58 (8) ◽  
pp. 815-822 ◽  
Author(s):  
K. Lindström ◽  
F. Österberg
Keyword(s):  
Reaction Mechanism ◽  
Melting Point ◽  
Structure Determination ◽  
Kraft Pulp ◽  
Chemical Shifts ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
Chemical Pulp ◽  
C Nmr

3,4,5-Trichloroguaiacol, which is formed during bleaching of chemical pulp and shown to bioaccumulate in fish, has been synthesized. The structure of the compound has been determined by means of X-ray analysis. The values of the 13C nmr chemical shifts and melting point differ from those previously reported. A reaction mechanism is suggested for the formation of 3,4,5- and 4,5,6-trichloroguaiacol.

Preparation, 1H and 13C NMR, and ab initio/IGLO study of mono-O-protonated deltic acid and theoretical investigation of di-, tri-, and tetra-O-protonated deltic acids

1999 ◽  
Vol 77 (5-6) ◽  
pp. 525-529 ◽  
Author(s):  
GK Surya Prakash ◽  
Golam Rasul ◽  
George A Olah ◽  
Ronghua Liu ◽  
Thomas T Tidwell
Keyword(s):  
Nmr Spectroscopy ◽  
Ab Initio ◽  
Theoretical Investigation ◽  
13C Nmr ◽  
Chemical Shifts ◽  
1H And 13C Nmr ◽  
Nmr Chemical Shifts ◽  
Molar Solution ◽  
Protonated Species ◽  
C Nmr

The hitherto elusive mono-O-protonated deltic acid C3O3H3+ was prepared by protolysis of di-tert-butoxy deltate in FSO3H-SO2ClF and in FSO3H:SbF5 (Magic Acid; 1:1 molar solution) in SO2ClF as solvent at -78°C and was characterized by 1H and 13C NMR spectroscopy. The structure and NMR chemical shifts were also calculated by the ab initio/IGLO method. No NMR evidence was found for persistent di-O-protonated deltic acid under these conditions, although a limited equilibrium with the mono-O-protonated species can be involved. Di-, tri-, and tetra-O-protonated deltic acids were also studied by ab initio/IGLO method.Key words: protonated deltic acid, aromaticity, superacids, NMR spectroscopy, ab initio and IGLO calculations.

scholarly journals Substituenteneinflüsse auf die 13C–NMR-chemischen Verschiebungen cis- und trans-konfigurierter Trimethincyanine / Substituent Effects on the 13C NMR Chemical Shifts of Trimethincyanines with cis and trans Configuration

1976 ◽  
Vol 31 (12) ◽  
pp. 1641-1645 ◽  
Author(s):  
Walter Grahn
Keyword(s):  
13C Nmr ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron Systems ◽  
Coupling Constant ◽  
Electronic Effects ◽  
Nmr Chemical Shifts ◽  
Monosubstituted Benzenes ◽  
Cis And Trans ◽  
C Nmr

The 13C NMR chemical shifts of fifteen 6 substituted 2,3-dihydro-1,4-diazepinium salts (cis trimethincyanines) (1) and twelve 2 substituted bis(dimethylamino)trimethinium salts (trans trimethincyanines) (2) have been determined. A comparison of the substituentinduced shifts (13C SCS) of 1 and 2 allows no distinction between steric and electronic effects. In the three 6 п-electron systems 1, 2 and monosubstituted benzenes the 13C SCS are similar for the substituent bearing carbon atoms. A surprisingly large 4JFCCNC coupling constant has been observed.

scholarly journals Bridge effect of the C=C, C=N and N=N bonds on the long distance electronic charge transfer ofpara‒substituted stilbenoid compounds

2000 ◽  
Vol 14 (4) ◽  
pp. 259-267 ◽  
Author(s):  
Manuel A. Leiva ◽  
Raul G. E. Morales
Keyword(s):  
Charge Transfer ◽  
Double Bond ◽  
Molecular System ◽  
Chemical Shifts ◽  
Phenyl Group ◽  
Point Of View ◽  
Electronic Charge ◽  
Orbital Theory ◽  
Long Distance ◽  
C Nmr

By means of13C‒NMR spectroscopy and ab initio molecular orbital theory calculations, we have analyzed the bridge effect of the C=C, C=N and N=N bonds on the long distance charge transfer of4‒dimethylamino‒4'‒nitrostilbenoid compounds in the ground electronic state.After a complete spectral assignment of the13C‒NMR signals in these molecular compounds, we have characterized the effect of the nitrogen centres on the molecular bridge by means of the chemical shifts of the carbon centres, the theoretical charge densities and the dipolar moments.From an electronic molecular point of view, our results describe two main properties of the double bond bridge. The first is related to the local charge accumulation capacity given by the type of the atomic centres and the structural orientation of the double bond bridge, and the second property is related to the modulation of the electronic charge distribution through the molecular system by the electrical polarization of the bridge.Other complementary experimental evidences have permit us to establish new local molecular domains of the bridge effect in these stilbenoid compounds by means of linear correlations between13C‒NMR chemical shifts of the aromatic carbon centres of the acceptor‒phenyl group and the molecular polarity of the species under study.

Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2/3/4-Substituted Phenyl)-2,4-Disubstituted Benzenesulphonamides, 2,4-(CH3)2/2-CH3-4-Cl/2,4-Cl2C6H3SO2NH(i-XC6H4) (i-X = H, 2-CH3, 3-CH3, 4-CH3, 2-Cl, 3-Cl, 4-Cl, 4-F, 4-Br)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 600-606
Author(s):  
Savitha M. Basappa ◽  
Basavalinganadoddy Thimme Gowda
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Spectral Studies ◽  
1H And 13C Nmr ◽  
Nmr Chemical Shifts ◽  
Benzene Rings ◽  
Stretching Vibrations ◽  
Absorption Frequencies ◽  
C Nmr

Twenty six N-(2/3/4-substituted phenyl)-2,4-disubstituted benzenesulphonamides of the general formulae 2,4-(CH3)2C6H3SO2NH(i-XC6H4), 2-CH3-4-ClC6H3SO2NH(i-XC6H4) and 2,4- Cl2C6H3SO2NH(i-XC6H4), where i-X = H, 2-CH3, 3-CH3, 4-CH3, 2-Cl, 3-Cl, 4-Cl, 4-F or 4-Br, have been prepared, characterized and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution studied. The infrared N-H stretching vibrational frequencies vary in the range 3298 - 3233 cm−1. Asymmetric and symmetric SO stretching vibrations appear in the ranges 1373 - 1311 cm−1 and 1177 - 1140 cm−1, respectively, while C-S, S-N and C-N stretching absorptions vary in the ranges 840 - 812 cm−1, 972 - 908 cm−1 and 1295 - 1209 cm−1, respectively. The various 1H and 13C NMR chemical shifts are assigned to the protons and carbon atoms of the two benzene rings in line with those for similar compounds. The incremental shifts due to the groups in the parent compounds have been computed by comparing the chemical shifts of the protons or carbon atoms in these compounds with those of benzene or aniline, respectively. The computed incremental shifts and other data were used to calculate the 1H and 13C NMR chemical shifts of the substituted compounds in three different ways. The calculated chemical shifts by the three methods compared well with each other and with the observed chemical shifts. It is observed that there are no particular trends in the variation of either the infrared absorption frequencies or the chemical shifts with the nature or site of substitution.

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