scholarly journals The syntheses and NMR studies of hexadeca- and octaneopentoxyphthalocyanines

2002 ◽  
Vol 80 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Namrta Bhardwaj ◽  
John Andraos ◽  
Clifford C Leznoff
Keyword(s):  
Nmr Spectra ◽  
Variable Temperature ◽  
Nickel Chloride ◽  
Nmr Studies ◽  
Restricted Rotation ◽  
H Nmr

The syntheses of 3,6-dineopentoxyphthalonitrile and 3,4,5,6-tetraneopentoxyphthalonitrile are described. Condensation of these phthalonitriles with nickel chloride in N,N-dimethylaminoethanol yielded 1,4,8,11,15,18,22,25-octaneopentoxyphthalocyaninato nickel(II) (3) and 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecaneopentoxyphthalocyaninato nickel(II) (7). The 1H NMR spectra of these phthalocyanines and the related 2,3,9,10,16,17,23,24-octaneopentoxyphthalocyaninato nickel(II) (8) at temperatures from 205 to 330 K in toluene-d8 exhibited various degrees of restriction of rotation of the neopentoxy groups. Compound 7 exhibited a single atropisomer at 235 K.Key words: neopentoxy substituted phthalocyanines, variable temperature NMR, restricted rotation.

Rotationsbarriere der Endgruppen bei Poly- methinoxonolen verschiedener Kettenlänge / Rotation Barrier of the End Groups of Polymethine Oxonols with Different Chain Lengths

1976 ◽  
Vol 31 (8) ◽  
pp. 1017-1018 ◽  
Author(s):  
H. Oehling ◽  
F. Baer
Keyword(s):  
Nmr Spectra ◽  
Rotation Barrier ◽  
Free Enthalpy ◽  
Temperature Dependent ◽  
Restricted Rotation ◽  
H Nmr ◽  
Enthalpy Of Activation ◽  
End Groups ◽  
Electron Contribution ◽  
Chain Lengths

Abstract Polymethine oxonols show temperature dependent 1H-NMR-spectra because of restricted rotation of the end groups. The dependence of the value of the corresponding free enthalpy of activation AGt on the length of the poly-methine chain can be explained by the change of the π-electron contribution to ⊿G≠.

Chiral "basket handle" binaphthyl porphyrins: synthesis, catalytic epoxidation and NMR conformational studies

2010 ◽  
Vol 14 (07) ◽  
pp. 646-659 ◽  
Author(s):  
Eric Rose ◽  
Emma Gallo ◽  
Nicolas Raoul ◽  
Léa Bouché ◽  
Ariane Pille ◽  
...  
Keyword(s):  
Time Scale ◽  
Room Temperature ◽  
Conformational Equilibrium ◽  
Variable Temperature ◽  
Conformational Exchange ◽  
Iron Catalysts ◽  
Nmr Studies ◽  
Conformational Studies ◽  
H Nmr ◽  
Catalytic Epoxidation

Three "basket handle" porphyrins have been prepared by condensation of tetrakis-(α,β,α,β-2-aminophenyl)porphyrin atropoisomer with 1,1′-binaphthyl, 2,2′-dimethoxy, -3,3′-dicarbonylchloride, -3,3′-diacetylchloride and -3,3′-dipropanoylchloride. The epoxidation of styrene with the three iron catalysts, obtained after metalation of the free porphyrins, occurs with good yields and moderate ee up to 54%. These porphyrins showed unexpected conformational differences, as revealed by NMR spectroscopy. In particular, variable temperature NMR studies showed that the methoxy group in one of them undergoes intermediate conformational exchange on the 1H NMR time scale at room temperature. Lowering the temperature to -50 °C revealed the presence of four states in slow exchange on the NMR time scale. These results evidence a dynamic conformational equilibrium of the binaphthyl handles that adopt different, asymmetric positions with respect to the porphyrin plane.

Nuclear magnetic resonance studies of the methylammonium hexahalotellurates

1992 ◽  
Vol 70 (3) ◽  
pp. 849-855 ◽  
Author(s):  
Mark R. MacIntosh ◽  
Marco L. H. Gruwel ◽  
Katherine N. Robertson ◽  
Roderick E. Wasylishen
Keyword(s):  
Line Shape ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Solid Phase ◽  
Variable Temperature ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
H Nmr ◽  
Nmr Study ◽  
Correlated Motion

A 2H and 14N NMR study of the solid methylammonium hexahalotellurates, (MA)2TeX6 (MA = CH3ND3+ or CD3NH3+, X = Cl, Br, and I), has been undertaken to characterize the dynamics of the methylammonium (MA) ion as a function of temperature. At room temperature, the MA ion in the hexachlorotellurate (solid II) is confined to C3 jumps about the C—N axis while a small angle libration of the C—N axis is occurring. In the room temperature phase, solid I, of (MA)2TeBr6 and (MA)2TeI6 the MA ions are performing overall reorientations on the ps time scale, averaging the 2H nuclear quadrupolar interactions to zero. Variable temperature 2H NMR spin-lattice relaxation times, T1, indicate an activation energy, EA, for "isotropic" reorientations of the CH3ND3+ ion of 5.2 ± 0.5 and 2.6 ± 0.3 kJ mol−1 for X = Br and I, respectively. Deuterium T1 values for C-deuterated MA ion in the hexaiodotellurate indicate an EA for whole-ion reorientation of 3.1 ± 0.3 kJ mol−1. At any given temperature, the correlation time, τc, derived from the T1 results was found to be the same for the two deuterium-labelled hexaiodotellurates. The similarity of both the EA and the τc values implies correlated motion of the methyl and ammonium groups. The 14N T1 results for solid I of (MA)2TeI6 indicate that C—N axis motions, with an EA = 5.6 ± 0.6 kJ mol−1, are more hindered than N—D or C—D bond dynamics. The 2H NMR spectra for (MA)2TeI6 (solid II) and (MA)2TeBr6 (solids II, III, and IV) are characterized by a Pake doublet line shape. The measured peak-to-peak splittings are less than what is predicted by C3 motion about the molecular symmetry axis. It is possible to model these line shapes by postulating that C3 rotations of the methyl and ammonium groups occur as the C—N axis librates in an effective cone about the position of the static molecular axis. For (CH3ND3)2TeBr6 and (CD3NH3)3TeBr6 the peak-to-peak splittings in the 2H NMR spectra were measured as a function of temperature in solid phases II, III, and IV and were found to be similar. Finally, the 2H NMR line shape relaxation for (MA)2TeBr6 (solid III) displays an orientation dependence indicating that rotations about the C—N axis are discrete rather than diffusive in nature. For solid phase II of (MA)2TeCl6, the line shape is observed to relax isotropically, implying that continuous C3 rotations are taking place. Keywords: 2H and 14N NMR, methylammonium hexahalotellurates, molecular motion.

A simple 1H nmr conformational study of some heterocyclic azomethines

1981 ◽  
Vol 59 (8) ◽  
pp. 1205-1207 ◽  
Author(s):  
Francesco A. Bottino ◽  
Maria L. Longo ◽  
Domenico Sciotto ◽  
Michele Torre
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shift ◽  
Intramolecular Hydrogen Bond ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Rotational Isomerism ◽  
Conformational Study ◽  
Pyrrole Derivatives ◽  
H Nmr ◽  
Intramolecular Hydrogen

The variable temperature 60 MHz 1H nmr spectra of some heterocyclic azomethines exclude the presence of rotational isomerism. Chemical shift values and stereospecific long-range couplings are used to establish that s-trans is the existing conformation. In the case of the pyrrole derivatives a chelated s-trans rotamer is indicated, depending on the presence of an intramolecular hydrogen bond.

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1057-1065
Author(s):  
John T Edward ◽  
Francis L Chubb ◽  
Denis FR Gilson ◽  
Rosemary C Hynes ◽  
Françoise Sauriol ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Acidic Solution ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
Cage Compounds ◽  
Amine Nitrogen ◽  
X Ray ◽  
Bridgehead Nitrogen ◽  
C Nmr

Three new cage peroxides, 1,6-diaza-3,4,8,9-tetraoxabicyclo[4.4.2]dodecane (3a),1,6-diaza-3,4,8,9-tetraoxa-11-methylbicyclo[4.4.2]dodecane (3b), and 1,6-diaza-3,4,8,9-tetraoxatricyclo[4.4.2.411,12]hexadecane (4), have been prepared by reaction of 1,2-diaminoethane, 1,2-diaminopropane, and trans-1,2-diaminocyclohexane, respectively, with formaldehyde and hydrogen peroxide in aqueous acidic solution. Their structures have been established by X-ray diffraction, and show the bridgehead nitrogen atoms to be predominantly sp2 hybridized. The structures accord with 1H and 13C NMR spectra. Variable temperature NMR studies show that the diperoxide 3a begins to undergo rapid inversion (on the NMR time scale) at about 303 K; up to 370 K the diperoxides 3b and 4 show no conformational change.Key words: cage compounds, formaldehyde, peroxides, amine nitrogen, hybridization.

Purine Nucleoside Analogues. 11. An Alternative Synthesis of N- and O-Alkyl Derivatives of 9- and 7-[(2-Acetoxyethoxy)methyl]-N2-acetylguanine

1999 ◽  
Vol 64 (4) ◽  
pp. 685-695 ◽  
Author(s):  
Marina Madre ◽  
Natella Panchenko ◽  
Alexander Golbraikh ◽  
Regina Zhuk ◽  
Upendra K. Pandit ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Room Temperature ◽  
Purine Nucleoside ◽  
Nucleoside Analogues ◽  
Alternative Synthesis ◽  
Restricted Rotation ◽  
H Nmr ◽  
Alkyl Derivatives ◽  
Derivatives Of ◽  
Conformational Calculations

Alkylations of 9- and 7-[(2-acetoxyethoxy)methyl]-N2-acetylguanine with alkyl halogenides in the presence of base have been investigated affording a new route to the preparation of 1,N2-dimethyl- as well as O6-benzyl-9(7)-alkoxyalkylguanines. 1H NMR spectra revealed that the 1,N2-dimethyl derivatives exist as mixtures of two conformers at room temperature due to the restricted rotation about the C2-N2 bond. These findings agreed with conformational calculations.

Synthesis and conformational analysis of porphyrin derivatives substituted with calix[4]arene subunits

2011 ◽  
Vol 15 (11n12) ◽  
pp. 1183-1188 ◽  
Author(s):  
Michel Holler ◽  
Michel Schmitt ◽  
Jean-François Nierengarten
Keyword(s):  
Conformational Analysis ◽  
Variable Temperature ◽  
Restricted Rotation ◽  
H Nmr ◽  
Porphyrin Derivatives ◽  
Complete Series ◽  
Dynamic Phenomena

The synthesis of a complete series of calix[4]arene-substituted porphyrins is described. A detailed conformational analysis based on variable-temperature 1H NMR experiments revealed dynamic phenomena arising from the restricted rotation around the calix[4]arene-porphyrin bond.

Lewis acidic titanium species: the synthesis, structure, bonding and molecular modelling considerations of the complexes Ti(NR2)3Cl (R = Me, Et)

1991 ◽  
Vol 69 (2) ◽  
pp. 357-362 ◽  
Author(s):  
David G. Dick ◽  
Roger Rousseau ◽  
Douglas W. Stephan
Keyword(s):  
Molecular Modelling ◽  
Energy Minimization ◽  
Variable Temperature ◽  
Structural Data ◽  
Steric Effects ◽  
Monoclinic Space Group ◽  
Nmr Studies ◽  
Space Group ◽  
H Nmr ◽  
Multiple Bonding

Reaction of simple amides with TiCl4 affords mixed amido-chloride species Ti(NR2)4−nCln. The trisamide-chloride species Ti(NR2)3Cl can be prepared directly employing three equivalents of amide or by reaction Ti(NR2)4 with TiCl4. The compound Ti(NMe2)3Cl, 1, crystallizes in the trigonal space group [Formula: see text] with a = 11.525(5), c = 14.939(3) Å, Z = 6, and V = 1718(1) Å3. The compound Ti(NEt2)3Cl, 2, crystallizes in the monoclinic space group P21/c, with a = 8.385(2) Å, b = 15.958(2) Å, c = 14.230(4) Å, β = 107.79(1)°, Z = 4, and V = 1813(1) Å3. The geometry of the Ti coordination sphere in these complexes is best described as pseudo-tetrahedral. The structural data are consistent with Ti—N multiple bonding. Preliminary results of EHMO calculations are consistent with dπ—pπ Ti—N bonding. Attempts to replace the halides with phosphides (LiPR2, R = Me, Et, Ph) led not to the Ti(IV) phosphido species, but rather to redox chemistry yielding Ti(III) amides and P2R4. The barrier to rotation about the Ti—N bonds has been considered. Variable temperature 1H NMR studies reveal that the barrier is small. Extended Hückel total energy minimization calculations have been performed. In addition, MMX calculations of the barrier to Ti—N rotation are reported. The results of these calculations imply that the rotational barrier is dominated by steric effects. Key words: titanium amides, structures, Ti—N bonding

Phenylsilane dehydrocoupling and addition to styrene catalyzed by (R-indenyl)Ni(phosphine)(methyl) complexes

2009 ◽  
Vol 87 (1) ◽  
pp. 280-287 ◽  
Author(s):  
Yaofeng Chen ◽  
Davit Zargarian
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Structural Parameters ◽  
Catalytic Cycle ◽  
Synthesis And Characterization ◽  
H Nmr ◽  
Solid State Structures ◽  
Indenyl Complexes

This report describes the synthesis and characterization of the Ni–Me complexes (R-indenyl)Ni(PR′3)Me (R = 1-i-Pr, 1-SiMe3, and 1,3-(SiMe3)2; R′= Me, Ph) and outlines their catalytic reactivities in the dehydrogenative oligomerization of PhSiH3 and its addition to styrene in the absence of initiators/activators. Observation of higher hydrosilylation activities for PPh3-based compounds featuring bulky substituents on the indenyl ligand confirms earlier suggestions that phosphine dissociation is an important component of the catalytic cycle for this reaction. In contrast, oligomerization of PhSiH3 is more facile with PMe3-based precursors and independent of the steric bulk of the indenyl ligand, implying that this reaction does not involve phosphine dissociation. These conclusions are consistent with the variable-temperature 1H NMR spectra of {1,3,-(SiMe3)2-indenyl}Ni(PR′3)Me and various structural parameters observed in the solid-state structures of {1,3,-(SiMe3)2-indenyl}Ni(PPh3)Me, {1,3,-(SiMe3)2-indenyl}Ni(PMe3)Cl, and {1-SiMe3-indenyl}Ni(PMe3)Me.Key words: nickel-indenyl complexes, hydrosilylation, hydrosilane oligomerization.

Trihapto cycloheptatrienyl molybdenum and tungsten dicarbonyl compounds incorporating tridentate chelating dimethyl(1-pyrazolyl)(ethanolamine)gallate ligands

1980 ◽  
Vol 58 (21) ◽  
pp. 2278-2285 ◽  
Author(s):  
Kenneth S. Chong ◽  
Alan Storr
Keyword(s):  
Nitrogen Atom ◽  
Low Temperature ◽  
Physical Properties ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Amino Nitrogen ◽  
Nmr Studies ◽  
Dicarbonyl Compounds ◽  
H Nmr ◽  
And Tungsten

The synthesis and physical properties of a series of cycloheptatrienyl molybdenum and tungsten dicarbonyl compounds incorporating dimethyl(1-pyrazolyl)(ethanolamine)gallate ligands have been investigated. The monomeric, pseudo octahedral, complexes have the organogallate ligand occupying a set of facial positions with the cycloheptatrienyl ring situated opposite to the amino nitrogen atom. Proton nmr studies have shown the η3-C7H7 ligand of the complexes to be fluxional in solution at room temperature. In the low temperature limiting 1H nmr spectra of the complexes in solution, however, it is possible to distinguish ail seven protons of the static η3-C7H7 ring owing to the asymmetric nature of the octahedral molecules.

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