Optimization of molecular geometry of para-substituted benzoic acids and their anions by means of gradient CNDO/2 method

1982 ◽  
Vol 47 (12) ◽  
pp. 3393-3404 ◽  
Author(s):  
Stanislav Böhm ◽  
Josef Kuthan
Keyword(s):  
Diffraction Data ◽  
Molecular Geometry ◽  
Benzoic Acids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Substituted Benzoic Acids

21 conformers of benzoic acids I and corresponding anions II have been optimized by the title semiempirical MO approach. The calculated geometry characteristics are confronted systematically with X-ray diffraction data, and quality of the calculated parameters is critically evaluated.

Optimization of molecular geometry of meta-substituted benzoic acids and their anions by gradient CNDO/2 method

1983 ◽  
Vol 48 (4) ◽  
pp. 1019-1029 ◽  
Author(s):  
Stanislav Böhm ◽  
Josef Kuthan
Keyword(s):  
Degrees Of Freedom ◽  
Molecular Geometry ◽  
Published Data ◽  
Benzoic Acids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Substituted Benzoic Acids

32 conformers of meta-substituted benzoic acids I and the corresponding anions II have been optimized with respect to all geometrical degrees of freedom by the title semiempirical MO approach. The calculated geometry characteristics are compared with some published data obtained by means of X-ray diffraction.

Molecular Cocrystals of Carboxylic Acids. XXVI Adducts of the Amino-Substituted Benzoic Acids with Nitroaromatic Lewis Bases: the Influence of Associative Polyfunctional Substituents on Self-Assembly of Molecules in Cocrystallization Processes

1997 ◽  
Vol 50 (10) ◽  
pp. 977 ◽  
Author(s):  
Daniel E. Lynch ◽  
Graham Smith ◽  
Karl A. Byriel ◽  
Colin H. L. Kennard
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectroscopy ◽  
Self Assembly ◽  
Benzoic Acids ◽  
Aminobenzoic Acid ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lewis Bases ◽  
Aminobenzoic Acids ◽  
Substituted Benzoic Acids

A series of molecular adducts of the isomeric aminobenzoic acids with the nitro-substituted Lewis bases 2-chloro-5-nitropyridine, 5-nitroquinoline and 5-nitroisoquinoline has been prepared and characterized by using infrared spectroscopy and X-ray powder diffraction, and in four cases by single-crystal X-ray diffraction methods. These four compounds are the adducts of 3-aminobenzoic acid with 5-nitroquinoline [(C7H7NO2)(C9H6N2O2)], 4-aminobenzoic acid with 5-nitroquinoline [(C7H7NO2)2(C9H6N2O2)], 2-aminobenzoic acid with 5-nitroisoquinoline [(C7H7NO2)(C9H6N2O2)] and 4-aminobenzoic acid with 5-nitroisoquinoline [(C7H7N2O2)(C9H6N2O2)]. Other compounds described are the (1 : 1) adducts of 4-aminobenzoic acid with 2-chloro-5-nitropyridine, and 2-aminobenzoic acid with 5-nitroquinoline. All adducts involve hydrogen-bonding network associations while in none of the examples is any proton transfer involved.

Molecular Cocrystals of Carboxylic Acids. XIII. Spectral Characterization of the Adducts of Triphenylphosphine Oxide With Substituted Benzoic Acids and the Crystal Structures of the 1 : 1 Adducts With 2,4,6-Trinitrobenzoic Acid and 3,5-Dinitrobenzoic Acid

1993 ◽  
Vol 46 (10) ◽  
pp. 1535 ◽  
Author(s):  
DE Lynch ◽  
G Smith ◽  
NJ Calos ◽  
CHL Kennard ◽  
AK Whittaker ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Triphenylphosphine Oxide ◽  
Benzoic Acids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acid Proton ◽  
Phosphoryl Oxygen ◽  
Substituted Benzoic Acids ◽  
Convenient Technique

The 1:1 adducts of triphenylphosphine oxide with the 2-, 3- and 4-nitro-, 3,5-dinitro-, and 2,4,6-trinitro-substituted benzoic acids have been prepared, and characterized by infrared and 31P n.m.r. spectroscopy. The crystal structures of two of these adducts, (triphenylphosphine oxide-3,5-dinitrobenzoic acid) and ( triphenylphosphine oxide-2,4,6-trinitrobenzoic acid), have been determined by X-ray diffraction. In all examples, the presence of single directed hydrogen bonds between the phosphoryl oxygen and the carboxylic acid proton is confirmed. For the X-ray structures, the O…O distances are 2.54(4) and 2.55(1)Ǻ respectively. Solid-state 31P n.m.r. spectroscopy has also proved a convenient technique for the detection of the presence of a single conformational adduct type in cocrystals.

scholarly journals Diamonds in the rough: a strong case for the inclusion of weak-intensity X-ray diffraction data

2014 ◽  
Vol 70 (5) ◽  
pp. 1491-1497 ◽  
Author(s):  
Jimin Wang ◽  
Richard A. Wing
Keyword(s):  
Electron Density ◽  
Diffraction Data ◽  
Heavy Atom ◽  
Uniform Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Correlation ◽  
Atomic Models ◽  
Weak Intensity

Overwhelming evidence exists to show that the inclusion of weak-intensity, high-resolution X-ray diffraction data helps improve the refinement of atomic models by imposing strong constraints on individual and overall temperatureBfactors and thus the quality of crystal structures. Some researchers consider these data to be of little value and opt to discard them during data processing, particularly at medium and low resolution, at which individualBfactors of atomic models cannot be refined. Here, new evidence is provided to show that the inclusion of these data helps to improve the quality of experimental phases by imposing proper constraints on electron-density models during noncrystallographic symmetry (NCS) averaging. Using electron-density correlation coefficients as criteria, the resolution of data has successfully been extended from 3.1 to 2.5 Å resolution with redundancy-independent mergingRfactors from below 100% to about 310%. It is further demonstrated that phase information can be fully extracted from observed amplitudes throughde novoNCS averaging. Averaging starts with uniform density inside double-shelled spherical masks and NCS matrices that are derived from bound heavy-atom clusters at the vertices of cuboctahedrally symmetric protein particles.

XRD Instrument Sensitivity Results from a Round Robin Study

1991 ◽  
Vol 35 (A) ◽  
pp. 333-340 ◽  
Author(s):  
W.N. Schreiner ◽  
R. Jenkins ◽  
P.F. Dismore
Keyword(s):  
Diffraction Data ◽  
Round Robin ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Diffraction Intensity ◽  
Generic Type ◽  
X Ray ◽  
The Past ◽  
Instrument Sensitivity

During the course of the past ten years the International Centre for Diffraction Data has sponsored a number of “Round Robin” tests to evaluate the quality of experimental X-ray diffraction data [1-5]. The latest of this series, called the Instrument Parameter Round Robin, was designed to evaluate, among other things, relative angularly-dependent sensitivity differences between diffractometers. Previous experiments have indicated that even perfectly aligned diffractometers of the same generic type, do not necessarily give the same set of relative intensities. One objective of the round robin was to quantify the magnitude of the experimental differences between data sets, and to demonstrate a means for external calibration of diffractometers, so that digitized diffraction intensity data obtained from different instruments could be directly compared.

scholarly journals Comparison of the Quality of Protein Crystals Grown by CLPC Seeds Method

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 501 ◽  
Author(s):  
Li ◽  
Yan ◽  
Liu ◽  
Wu ◽  
Liu ◽  
...  
Keyword(s):  
Diffraction Data ◽  
Protein Crystal ◽  
Protein Crystals ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
High Quality Protein

We present a systematic quality comparison of protein crystals obtained with and without cross-linked protein crystal (CLPC) seeds. Four proteins were used to conduct the experiments, and the results showed that crystals obtained in the presence of CLPC seeds exhibited a better morphology. In addition, the X-ray diffraction data showed that the CLPC seeds method is a powerful tool to obtain high-quality protein crystals. Therefore, we recommend the use of CLPC seeds in preparing high-quality diffracting protein crystals.

Designing Linear Hydrogen-Bonded Arrays by Using Substituted Charge-Transfer Complexes. The Crystal Structure of the 1 : 1 Adduct of Indole-2-carboxylic Acid with 3,5-Dinitrobenzoic Acid

1998 ◽  
Vol 51 (11) ◽  
pp. 1019 ◽  
Author(s):  
Daniel E. Lynch ◽  
Graham Smith ◽  
Karl A. Byriel ◽  
Colin H. L. Kennard
Keyword(s):  
Crystal Structure ◽  
Carboxylic Acid ◽  
Second Harmonic ◽  
Charge Transfer Complexes ◽  
Benzoic Acids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Linear Optical Properties ◽  
Substituted Benzoic Acids ◽  
Indole 3 Acetic Acid

Five adducts consisting of carboxylic acid-substituted indoles with nitro-substituted benzoic acids have been synthesized and tested for second-order non-linear optical properties. These were indole-2-carboxylic acid with 2,4-dinitrobenzoic acid (1), 3,5-dinitrobenzoic acid (2), and 2,4,6-trinitrobenzoic acid (3), and indole-3-acetic acid with 3,5-dinitrobenzoic acid (4), and 2,4,6-trinitrobenzoic acid (5). Compound (2) produced clear, yellow crystals (space group P -1 with a 6·8400(7), b 15·150(2), c 16·097(2) Å, α 84·911(9), β 87·088(10), γ 77·865(9)°, Z 4) which allowed the structure to be determined by X-ray diffraction. Of the five adducts, compounds (3) and (5) gave second harmonic intensities of 0·15 and 0·16 times respectively that of a urea standard.

On the quality of the continuous rotation electron diffraction data for accurate atomic structure determination of inorganic compounds

2018 ◽  
Vol 51 (4) ◽  
pp. 1094-1101 ◽  
Author(s):  
Yunchen Wang ◽  
Taimin Yang ◽  
Hongyi Xu ◽  
Xiaodong Zou ◽  
Wei Wan
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structural Models ◽  
Electron Diffraction Data ◽  
Data Sets ◽  
X Ray Diffraction ◽  
X Ray ◽  
Continuous Rotation

The continuous rotation electron diffraction (cRED) method has the capability of providing fast three-dimensional electron diffraction data collection on existing and future transmission electron microscopes; unknown structures could be potentially solved and refined using cRED data collected from nano- and submicrometre-sized crystals. However, structure refinements of cRED data using SHELXL often lead to relatively high R1 values when compared with those refined against single-crystal X-ray diffraction data. It is therefore necessary to analyse the quality of the structural models refined against cRED data. In this work, multiple cRED data sets collected from different crystals of an oxofluoride (FeSeO3F) and a zeolite (ZSM-5) with known structures are used to assess the data consistency and quality and, more importantly, the accuracy of the structural models refined against these data sets. An evaluation of the precision and consistency of the cRED data by examination of the statistics obtained from the data processing software DIALS is presented. It is shown that, despite the high R1 values caused by dynamical scattering and other factors, the refined atomic positions obtained from the cRED data collected for different crystals are consistent with those of the reference models refined against single-crystal X-ray diffraction data. The results serve as a reference for the quality of the cRED data and the achievable accuracy of the structural parameters.

Single-crystal x-ray diffraction structures of covalent organic frameworks

Science ◽  
2018 ◽  
Vol 361 (6397) ◽  
pp. 48-52 ◽  
Author(s):  
Tianqiong Ma ◽  
Eugene A. Kapustin ◽  
Shawn X. Yin ◽  
Lin Liang ◽  
Zhengyang Zhou ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
General Procedure ◽  
Three Dimensional ◽  
Electron Diffraction Data ◽  
Covalent Organic Frameworks ◽  
X Ray Diffraction ◽  
X Ray

The crystallization problem is an outstanding challenge in the chemistry of porous covalent organic frameworks (COFs). Their structural characterization has been limited to modeling and solutions based on powder x-ray or electron diffraction data. Single crystals of COFs amenable to x-ray diffraction characterization have not been reported. Here, we developed a general procedure to grow large single crystals of three-dimensional imine-based COFs (COF-300, hydrated form of COF-300, COF-303, LZU-79, and LZU-111). The high quality of the crystals allowed collection of single-crystal x-ray diffraction data of up to 0.83-angstrom resolution, leading to unambiguous solution and precise anisotropic refinement. Characteristics such as degree of interpenetration, arrangement of water guests, the reversed imine connectivity, linker disorder, and uncommon topology were deciphered with atomic precision—aspects impossible to determine without single crystals.

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