scholarly journals Chemically Fueled Transient Geometry Changes in Diphenic Acids

2020 ◽  
Author(s):  
Isuru Jayalath ◽  
Hehe Wang ◽  
Georgia Mantel ◽  
Lasith S. Kariyawasam ◽  
Scott Hartley
Keyword(s):  
Quantitative Analysis ◽  
Kinetic Parameters ◽  
Dihedral Angle ◽  
Steric Hindrance ◽  
Molecular Geometry ◽  
Torsional Angle ◽  
Fuel Treatment ◽  
Simple Mechanism ◽  
Ethylcarbodiimide Hydrochloride ◽  
Biochemical Systems

Transient changes in molecular geometry are key to the function of many important biochemical systems. Here, we show that diphenic acids undergo out-of-equilibrium changes in dihedral angle when reacted with a carbodiimide chemical fuel. Treatment of appropriately functionalized diphenic acids with EDC (<i>N</i>-(3-dimethylaminopropyl)-<i>N</i>′-ethylcarbodiimide hydrochloride) yields the corresponding diphenic anhydrides, reducing the torsional angle about the biaryl bond by approximately 45°, regardless of substitution. In the absence of steric resistance, the reaction is well-described by a simple mechanism; the resulting kinetic parameters can be used to derive important properties of the system, such as yields and lifetimes. The reaction tolerates steric hindrance ortho to the biaryl bond, although the competing formation of (transient) byproducts complicates quantitative analysis.

scholarly journals Chemically Fueled Transient Geometry Changes in Diphenic Acids

2020 ◽  
Author(s):  
Isuru Jayalath ◽  
Hehe Wang ◽  
Georgia Mantel ◽  
Lasith S. Kariyawasam ◽  
Scott Hartley
Keyword(s):  
Quantitative Analysis ◽  
Kinetic Parameters ◽  
Dihedral Angle ◽  
Steric Hindrance ◽  
Molecular Geometry ◽  
Torsional Angle ◽  
Fuel Treatment ◽  
Simple Mechanism ◽  
Ethylcarbodiimide Hydrochloride ◽  
Biochemical Systems

Transient changes in molecular geometry are key to the function of many important biochemical systems. Here, we show that diphenic acids undergo out-of-equilibrium changes in dihedral angle when reacted with a carbodiimide chemical fuel. Treatment of appropriately functionalized diphenic acids with EDC (<i>N</i>-(3-dimethylaminopropyl)-<i>N</i>′-ethylcarbodiimide hydrochloride) yields the corresponding diphenic anhydrides, reducing the torsional angle about the biaryl bond by approximately 45°, regardless of substitution. In the absence of steric resistance, the reaction is well-described by a simple mechanism; the resulting kinetic parameters can be used to derive important properties of the system, such as yields and lifetimes. The reaction tolerates steric hindrance ortho to the biaryl bond, although the competing formation of (transient) byproducts complicates quantitative analysis.

scholarly journals Relation between photochromic properties and molecular structures in salicylideneaniline crystals

2012 ◽  
Vol 68 (3) ◽  
pp. 297-304 ◽  
Author(s):  
Kohei Johmoto ◽  
Takashi Ishida ◽  
Akiko Sekine ◽  
Hidehiro Uekusa ◽  
Yuji Ohashi
Keyword(s):  
Dihedral Angle ◽  
Steric Hindrance ◽  
Molecular Structures ◽  
Dihedral Angles ◽  
Clear Correlation ◽  
X Ray Diffraction ◽  
Photochromic Properties ◽  
X Ray ◽  
Benzene Rings ◽  
The Relationship

The crystal structures of the salicylideneaniline derivatives N-salicylidene-4-tert-butyl-aniline (1), N-3,5-di-tert-butyl-salicylidene-3-methoxyaniline (2), N-3,5-di-tert-butyl-salicylidene-3-bromoaniline (3), N-3,5-di-tert-butyl-salicylidene-3-chloroaniline (4), N-3,5-di-tert-butyl-salicylidene-4-bromoaniline (5), N-3,5-di-tert-butyl-salicylidene-aniline (6), N-3,5-di-tert-butyl-salicylidene-4-carboxyaniline (7) and N-salicylidene-2-chloroaniline (8) were analyzed by X-ray diffraction analysis at ambient temperature to investigate the relationship between their photochromic properties and molecular structures. A clear correlation between photochromism and the dihedral angle of the two benzene rings in the salicylideneaniline derivatives was observed. Crystals with dihedral angles less than 20° were non-photochromic, whereas those with dihedral angles greater than 30° were photochromic. Crystals with dihedral angles between 20 and 30° could be either photochromic or non-photochromic. Inhibition of the pedal motion by intra- or intermolecular steric hindrance, however, can result in non-photochromic behaviour even if the dihedral angle is larger than 30°.

The Molecular Geometry of Diastereoisomeric Bis[α-(9-anthryl)ethyl] Ethers

1985 ◽  
Vol 38 (9) ◽  
pp. 1417 ◽  
Author(s):  
H Becker ◽  
VA Patrick ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Dihedral Angle ◽  
Molecular Geometry ◽  
Dihedral Angles ◽  
Methyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Meso Form ◽  
Aromatic Systems

The crystal structures of racemic bis [α-(9-anthryl)] ether and its meso form have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by least squares to residuals of 0.053 and 0.041 for 1868 and 3568 independent 'observed' reflections respectively. Crystals of the racemate are orthorhombic, Pcab, a 23.07(1), b 19.85(2), c 10.241(8) Ǻ, Z 8. Crystals of the meso form are triclinic, Pī , a 19.032(12), b 14.207(11), c 9.451(8) Ǻ, α 79.46(6), β 89.68(6), γ 68.97(5)°, Z 4. In the racemate , the dihedral angle between the methyl groups along the ether bonds is 12°, and the short axes of the anthracene moieties lie at an angle of about 120°. In the meso compound, for the two molecules the dihedral angles between the methyl groups along the ether bonds are 90 and 93°, the angle between the two anthracene moieties is 90°, and the interplanar angles between the partly overlapping aromatic systems are 46 and 43°.

2,6-Di-tert-butyl-4-(phenyliminomethyl)phenol

2006 ◽  
Vol 62 (4) ◽  
pp. o1455-o1456
Author(s):  
Xi-Long Yan ◽  
Li-Gong Chen ◽  
Tao Zeng
Keyword(s):  
Molecular Structure ◽  
Hydrogen Bond ◽  
Benzene Ring ◽  
Dihedral Angle ◽  
Hydroxy Group ◽  
Steric Hindrance ◽  
Phenyl Ring ◽  
Tert Butyl

In the title molecular structure, C21H27NO, the dihedral angle between the phenyl ring and the benzene ring planes is 63.28 (9) Å. It appears that the hydroxy group is prevented from forming a hydrogen bond because of steric hindrance by the tert-butyl groups.

Structures of strontium diformate and strontium fumarate. A synchrotron powder diffraction study

2009 ◽  
Vol 65 (4) ◽  
pp. 481-487 ◽  
Author(s):  
Kenny Ståhl ◽  
Jens E. T. Andersen ◽  
Irene Shim ◽  
Stephan Christgau
Keyword(s):  
Diffraction Study ◽  
Dihedral Angle ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Steric Hindrance ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Space Groups ◽  
Synchrotron Powder Diffraction ◽  
Δ Phase

The crystal structures of strontium diformate in space groups P212121 (α form, 295 K), P41212 (β form, 334 and 540 K) and I41/amd (δ form, 605 K), and strontium fumarate in space groups Fddd (β form, 105 K) and I41/amd (α form, 293 K) have been determined from synchrotron X-ray powder diffraction data. Except for the α-strontium diformate, all the structures are based on a diamond-like Sr-ion arrangement, as in strontium acetylene dicarboxylate. The formate ions are disordered in the δ phase owing to steric hindrance. The fumarate ions are disordered over four (α) or two (β) symmetry-equivalent orientations. α-Strontium fumarate crystallizes with a unique 90° carboxylate dihedral angle, and is stable up to 773 K.

scholarly journals Comparison among Reconstruction Algorithms for Quantitative Analysis of 11C-Acetate Cardiac PET Imaging

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ximin Shi ◽  
Nan Li ◽  
Haiyan Ding ◽  
Yonghong Dang ◽  
Guilan Hu ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Image Quality ◽  
Kinetic Parameters ◽  
Kinetic Modeling ◽  
Pet Imaging ◽  
Cardiac Pet ◽  
Reconstruction Algorithms ◽  
Time Points ◽  
Reconstruction Methods ◽  
Cardiac Pet Imaging

Objective. Kinetic modeling of dynamic 11C-acetate PET imaging provides quantitative information for myocardium assessment. The quality and quantitation of PET images are known to be dependent on PET reconstruction methods. This study aims to investigate the impacts of reconstruction algorithms on the quantitative analysis of dynamic 11C-acetate cardiac PET imaging. Methods. Suspected alcoholic cardiomyopathy patients (N=24) underwent 11C-acetate dynamic PET imaging after low dose CT scan. PET images were reconstructed using four algorithms: filtered backprojection (FBP), ordered subsets expectation maximization (OSEM), OSEM with time-of-flight (TOF), and OSEM with both time-of-flight and point-spread-function (TPSF). Standardized uptake values (SUVs) at different time points were compared among images reconstructed using the four algorithms. Time-activity curves (TACs) in myocardium and blood pools of ventricles were generated from the dynamic image series. Kinetic parameters K1 and k2 were derived using a 1-tissue-compartment model for kinetic modeling of cardiac flow from 11C-acetate PET images. Results. Significant image quality improvement was found in the images reconstructed using iterative OSEM-type algorithms (OSME, TOF, and TPSF) compared with FBP. However, no statistical differences in SUVs were observed among the four reconstruction methods at the selected time points. Kinetic parameters K1 and k2 also exhibited no statistical difference among the four reconstruction algorithms in terms of mean value and standard deviation. However, for the correlation analysis, OSEM reconstruction presented relatively higher residual in correlation with FBP reconstruction compared with TOF and TPSF reconstruction, and TOF and TPSF reconstruction were highly correlated with each other. Conclusion. All the tested reconstruction algorithms performed similarly for quantitative analysis of 11C-acetate cardiac PET imaging. TOF and TPSF yielded highly consistent kinetic parameter results with superior image quality compared with FBP. OSEM was relatively less reliable. Both TOF and TPSF were recommended for cardiac 11C-acetate kinetic analysis.

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