The chemistry of pyrrolic compounds. XLII. The synthesis of some diacetyldeuteroporphyrins as intermediates in the preparation of the isomeric protoporphyrins: a comparative spectroscopic study of the diacetyldeuteroporphyrins

1980 ◽  
Vol 33 (3) ◽  
pp. 545 ◽  
Author(s):  
PS Clezy ◽  
CJR Fookes
Keyword(s):  
Chemical Shift ◽  
Spectroscopic Study ◽  
Electronic Spectrum ◽  
Relative Position ◽  
Visible Spectrum ◽  
Oxidative Cyclization ◽  
Relative Distribution ◽  
Absorption Pattern ◽  
The One ◽  
Carbonyl Function

A range of isomeric diacetyldeuteroporphyrins has been synthesized by the oxidative cyclization of appropriately substituted bilenes-b, and the electronic and n.m.r. spectra of these porphyrins have been studied. As a result it has been shown that the relative position of the two acetyl groups influences the absorption pattern of the visible spectrum more precisely than was previously appreciated. In consequence, it is possible to recognize the 1,4, 2,3 and 2,4 relative distribution of the acetyl groups by an examination of the electronic spectrum. In addition, it is clear that the acetyl groups present in this series of porphyrins affect the chemical shift of all the methine protons and not only the one which is directly adjacent to the carbonyl function.

Intermolecular Interactions of Xe Atoms Confined in One-dimensional Nanochannels of Tris(o-phenylenedioxy)cyclotriphosphazene as Studied by High-pressure 129Xe NMR

2003 ◽  
Vol 58 (12) ◽  
pp. 727-734 ◽  
Author(s):  
Hirokazu Kobayashi ◽  
Takahiro Ueda ◽  
Keisuke Miyakubo ◽  
Taro Eguchi
Keyword(s):  
High Pressure ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Pressure Dependence ◽  
Average Distance ◽  
Chemical Shift Tensor ◽  
Axially Symmetric ◽  
One Dimensional ◽  
129Xe Nmr ◽  
The One

The pressure dependence of the 129Xe chemical shift tensor confined in the Tris(o-phenylenedioxy) cyclotriphosphazene (TPP) nanochannel was investigated by high-pressure 129Xe NMR spectroscopy. The observed 129Xe spectrum in the one-dimensional TPP nanochannel (0.45 nm in diameter) exhibits a powder pattern broadened by an axially symmetric chemical shift tensor. As the pressure increases from 0.02 to 7.0 MPa, a deshielding of 90 ppm is observed for the perpendicularcomponent of the chemical shift tensor δ⊥, whereas a deshielding of about 30 ppm is observed for the parallel one, δ‖. This suggests that the components of the chemical shift tensor, δ‖ and δ⊥, are mainly dominated by the Xe-wall and Xe-Xe interaction, respectively. Furthermore, the effect of helium, which is present along with xenon gas, on the 129Xe chemical shift is examined in detail. The average distance between the Xe atoms in the nanochannel is estimated to be 0.54 nm. This was found by using δ⊥ at the saturated pressure of xenon, and comparing the increment of the chemicalshift value in δ⊥ to that of a β -phenol/Xe compound.

A Surprising Formation of Novel Bridged Bis-Benzimidazoles by Oxidation of Diaminoquinoxalines

2012 ◽  
Vol 67 (4) ◽  
pp. 367-372 ◽  
Author(s):  
Jens Preßler ◽  
Rainer Beckert ◽  
Sven Rau ◽  
Roberto Menzel ◽  
Eckhard Birckner ◽  
...  
Keyword(s):  
Visible Spectrum ◽  
Oxidative Cyclization ◽  
Cyclization Reaction ◽  
High Melting ◽  
Strong Fluorescence ◽  
Blue Region ◽  
Derivatives Of

A synthesis of novel hexacyclic bis-benzimidazoles 6 starting from 2,3-diarylamino-quinoxalines via an oxidative cyclization cascade is described. These very stable and high-melting derivatives are featured by their strong fluorescence in the blue region of the visible spectrum. The cyclization reaction between 2,3-dichloroquinoxaline and 1,2-phenylenediamine did not lead to derivatives of type 6. In this case, only fluoflavine 7 was isolated quantitatively.

1H chemical shifts in nonaxial, paramagnetic chromium(III) complexes — Application of novel pNMR shift theory

2009 ◽  
Vol 87 (7) ◽  
pp. 954-964 ◽  
Author(s):  
Helmi Liimatainen ◽  
Teemu O. Pennanen ◽  
Juha Vaara
Keyword(s):  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Spin Symmetry ◽  
Nonrelativistic Limit ◽  
Chemical Application ◽  
Electronic Spin ◽  
Organic Complexes ◽  
Shielding Tensor ◽  
The One

We present the first chemical application of the recent, general theory of the nuclear magnetic resonance shielding and chemical shift in paramagnetic compounds, to a set of nonaxial high-spin metallo-organic complexes. The theory is for the first time rigorous for systems of arbitrary spatial and spin symmetry, and introduces new structure to the isotropic, anisotropic but symmetric, and anisotropic and antisymmetric parts of the shielding tensor. We apply the theory using density functional calculations of the proton chemical shift in a family of nonaxial chromium(III) complexes possessing a quartet ground electronic spin state. We discuss the various contributions to the isotropic chemical shift, and compare the full theory to approximate forms appropriate to the doublet case on the one hand, and to the doublet case at the nonrelativistic limit, on the other hand. The performance of various exchange-correlation functionals in reproducing the recently measured experimental chemical shifts is evaluated.

In Vivo 19F Mr Spectroscopic Study of Metabolism of 5-Fluorotryptophan in Rat Liver

1992 ◽  
Vol 33 (3) ◽  
pp. 258-261 ◽  
Author(s):  
M. Harada ◽  
H. Nishitani ◽  
K. Koga ◽  
I. Miura ◽  
R. Kido
Keyword(s):  
Chemical Shift ◽  
Liver Injury ◽  
Spectroscopic Study ◽  
Rat Liver ◽  
Mr Spectroscopy ◽  
Renal Excretion ◽  
Normal Liver ◽  
Injury Group ◽  
Injured Liver

The metabolism of 5-fluorotryptophan in rat liver was examined by in vivo 19F MR spectroscopy. After i.v. injection of 200 mg/kg b.w. of 5-fluorotryptophan the substance was noted immediately as a strong peak, which decreased gradually. Another peak appeared about 40 min after the injection. The chemical shift value of this peak was 1.6 ppm from that of 5-fluorotryptophan. Kynurenine is known to be a major metabolite of tryptophan in the liver. We synthesized 5-fluorokynurenine from 5-fluorotryptophan by ozonolysis. The chemical shift value of 5-fluorokynurenine was confirmed to be coincident with that of the metabolite peak. This strongly suggests that the metabolite peak of 5-fluorotryptophan observed in this study was the 5-fluorokyrurenine signal. We also applied this method for the CCl4-injured liver. In the liver injury group, the metabolite peak appeared slowly and the intensity was low compared to that of the normal group, though the peak of 5-fluorotryptophan decreased similarly as in the normal liver. These results suggest that the decrease of 5-fluorotryptophan is due mainly to the renal excretion, as the injured liver could not metabolize 5-fluorotryptophan.

scholarly journals NMR spectroscopic study of inclusion complexes of cetirizine dihydrochloride and β-cyclodextrin in solution

2007 ◽  
Vol 21 (3) ◽  
pp. 177-182 ◽  
Author(s):  
Syed Mashhood Ali ◽  
Santosh Kumar Upadhyay ◽  
Arti Maheshwari
Keyword(s):  
Aqueous Solution ◽  
Chemical Shift ◽  
Spectroscopic Study ◽  
Inclusion Complexes ◽  
Binding Constant ◽  
Spectroscopic Studies ◽  
Chemical Shift Change ◽  
Nmr Chemical Shift ◽  
H Nmr ◽  
Shift Change

Cetirizine dihydrochloride (CTZ), an antihistamine, forms two 1:1 inclusion complexes with β-cyclodextrin (β-CD) in aqueous solution as confirmed by detailed1H NMR, COSY and ROESY spectroscopic studies. The stoichiometry and overall binding constant of the complexes were determined by the treatment of1H NMR chemical shift change (Δδ) data. Most of the CTZ protons exhibited splitting in the presence of β-CD.

scholarly journals The locations of SNe Ib/c and their comparison to those of WR stars and GRBs

2011 ◽  
Vol 7 (S279) ◽  
pp. 191-198
Author(s):  
Giorgos Leloudas
Keyword(s):  
Star Formation ◽  
Spectroscopic Study ◽  
Massive Stars ◽  
Lower Mass ◽  
The Difference ◽  
The One

AbstractThe locations of long GRBs and stripped supernovae are compared to those of their favored progenitors, WR stars, and their sub-classes. Compared to Leloudas et al. (2010), we have doubled the number of galaxies with suitable WR data. In the combined sample, WC stars are found, on average, in brighter locations than WN stars. The WN distribution is fully consistent with the one of SNe Ib, while it is inconsistent with those of SNe II, Ic and GRBs. The WC distribution is both consistent with SNe Ib and Ic. It is inconsistent with SNe II, and marginally consistent with GRBs. Furthermore, we present a spectroscopic study of the locations of SNe Ib/c. The average metallicity in the environments of SNe Ic is found to be a little higher than for SNe Ib, but the difference is small and not significant within our sample. Under the assumption that the SN regions were formed in an instantaneous burst of star formation, we find that a fraction of them appear older than what is allowed in order to host SNe Ib/c from single massive stars. Within this framework, these SNe must come from lower mass binaries.

77Se NMR spectroscopic study of the molecular composition of sulfur–selenium melts

1992 ◽  
Vol 70 (3) ◽  
pp. 719-725 ◽  
Author(s):  
Tristram Chivers ◽  
Risto S. Laitinen ◽  
Kenneth J. Schmidt
Keyword(s):  
Nmr Spectroscopy ◽  
Spectroscopic Study ◽  
Polymeric Material ◽  
Nmr Spectra ◽  
Random Distribution ◽  
Relative Distribution ◽  
Selenium Content ◽  
Polymeric Chains ◽  
Melt Composition ◽  
Selenium Sulfide

A series of six sulfur–selenium mixtures containing 0.4, 5, 15, 25, 35, and 45 mol% of selenium were heated in evacuated ampoules at 430 °C for 4 h and, keeping the material molten at 135 °C, their natural-abundance 77Se NMR spectra were recorded. The equilibrium melt in each case was found to contain both heterocyclic SenS8−n species and polymeric material. The most abundant eight-membered selenium sulfide rings were SeS7, which was the main cyclic component in all melts studied in this work, and 1,2-Se2S6, the quantity of which increased with increasing selenium content of the melt. In addition the melts contained smaller amounts of 1,3, 1,4, and 1,5 isomers of Se2S6, 1,2,3, 1,2,4, and 1,2,5 isomers of Se3S5, 1,2,3,4, 1,2,3,5, and 1,2,5,6 isomers of Se4S4, 1,2,3,4,5-Se5S3, 1,2,3,4,5,6-Se6S2, and Se8. The relative distribution of the cyclic products as a function of the selenium content in the melt was virtually identical with that obtained earlier in the CS2 solutions of the quenched melts, implying that the extracted quenched melts actually represent the original melt composition as far as the SenS8−n species are concerned. The resonances due to the polymeric material in the melts could best be interpreted by the statistical random distribution of selenium and sulfur in the polymeric chains, the probability of occurrence of the different fragments being governed by the overall composition of the melt. As the selenium content increases, the relative amount of selenium bound in the polymer seems to increase at the expense of heterocyclic selenium sulfides. Keywords: selenium sulfides, sulfur–selenium melt, 77Se NMR spectroscopy.

ChemInform Abstract: Domino Oxidative Cyclization of 2-Aminoacetophenones for the One-Pot Synthesis of Tryptanthrin Derivatives.

ChemInform ◽  
2016 ◽  
Vol 47 (17) ◽  
Author(s):  
B. V. Subba Reddy ◽  
D. Maheswara Reddy ◽  
G. Niranjan Reddy ◽  
M. Ramana Reddy ◽  
V. Krishna Reddy
Keyword(s):  
Oxidative Cyclization ◽  
One Pot ◽  
One Pot Synthesis ◽  
The One

Bezier Curve Based Programmed Trajectory for Coordinated Motion of Two Robots in Cartesian Space

2014 ◽  
Vol 555 ◽  
pp. 192-198 ◽  
Author(s):  
Adam Slota
Keyword(s):  
Relative Position ◽  
Bézier Curve ◽  
Bezier Curve ◽  
Current Position ◽  
Coordinated Motion ◽  
Simulation Experiments ◽  
Cartesian Space ◽  
Position Errors ◽  
Different Shapes ◽  
The One

Coordinated motion of two robots in Cartesian space is considered in the paper. The goal is to generate trajectories for which change of distance between points on trajectories during motion is minimal. To minimize relative position errors along trajectories an idea of corrective motion is introduced. Trajectory coordinates are calculated as the sum of programmed and corrective motions. To calculate the speed vector of the programmed motion at the current position, the speed at the closest point on the programmed trajectory is used. The closest point is defined as the one to which the distance from the current position is minimal or the programmed position at given time. In order to attract the generated trajectory to the programmed one a modification of the programmed speed vector is proposed. The described approach is verified in simulation. For simulation experiments programmed trajectories defined by Bezier curve segments are used. Simulations for different shapes of programmed trajectories and different programmed velocity rates are presented.

Sign in / Sign up

Export Citation Format

Share Document