scholarly journals Structure and Properties of 1,3-Phenylenediboronic Acid: Combined Experimental and Theoretical Investigations

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 109 ◽  
Author(s):  
Agnieszka Adamczyk-Woźniak ◽  
Michał Cyrański ◽  
Krzysztof Durka ◽  
Jan Gozdalik ◽  
Paulina Klimentowska ◽  
...  
Keyword(s):  
Intermolecular Interaction ◽  
Molecular Conformation ◽  
Phenylboronic Acid ◽  
Topological Analysis ◽  
Intermolecular Forces ◽  
Hydroxyl Groups ◽  
Acidity Constant ◽  
Structure And Properties ◽  
Acid Base Equilibrium ◽  
Nmr Characterization

The structure and properties of 1,3-phenylenediboronic acid are reported. Molecular and crystal structures were determined by single crystal as well as by powder X-ray diffraction methods. Acidity constant, thermal behavior, and NMR characterization of the title compound were also investigated. In addition to the experimental data, calculations of rotational barrier and intermolecular interaction energies were performed. The compound reveals a two-step acid–base equilibrium with different pKa values. TGA and DSC measurements show a typical dehydration reaction with formation of boroxine. In crystals, hydrogen-bonded dimers with syn-anti conformation of hydroxyl groups form large numbers of ribbon motifs. The 2D potential energy surface scan of rotation of two boronic groups with respect to phenyl ring reveals that the rotation barrier is close to 37 kJ⋅mol−1, which is higher than the double value for the rotation of the boronic group in phenylboronic acid. This effect was ascribed to intermolecular interaction with C–H hydrogen atom located between boronic groups. Furthermore, the molecules in the crystal lattice adopt a less stable molecular conformation most likely resulting from intermolecular forces. These were further investigated by periodic DFT calculations supported by an estimation of dimer interaction energy, and also by topological analysis of electron density in the framework of AIM theory.

scholarly journals Structure and Properties of Oxidized Chitosan Grafted Cashmere Fiber by Amide Covalent Modification

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3812
Author(s):  
Jifeng Li ◽  
Ting Fang ◽  
Wenjing Yan ◽  
Fei Zhang ◽  
Yunhui Xu ◽  
...  
Keyword(s):  
Magic Angle Spinning ◽  
Covalent Modification ◽  
Primary Amines ◽  
Carboxyl Groups ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Structure And Properties ◽  
Carboxyl Content ◽  
Moisture Regain ◽  
Degree Structure

In this study, oxidized chitosan grafted cashmere fibers (OCGCFs) were obtained by crosslinking the oxidized chitosan onto cashmere fibers by amide covalent modification. A novel method was developed for the selective oxidation of the C6 primary hydroxyls into carboxyl groups for chitosan. The effect of oxidization reaction parameters of HNO3/H3PO4–NaNO2 mediated oxidation system on the oxidation degree, structure, and properties of chitosan were investigated. The chemical structure of the oxidized chitosan was characterized by solid-state cross-polarization magic angle spinning carbon-13 Nuclear Magnetic Resonance (CP/MAS 13C-NMR), Fourier transform infrared spectroscopy (FT-IR), and its morphology was investigated by scanning electron microscopy (SEM). Subsequently, the effect of the oxidized chitosan grafting on OCGCF was examined, and the physical properties, moisture regain, and antibacterial activity of OCGCFs were also evaluated. The results showed that oxidation of chitosan mostly occurred at the C6 primary hydroxyl groups. Moreover, an oxidized chitosan with 43.5–56.8% carboxyl content was realized by ranging the oxidation time from 30 to 180 min. The resulting OCGCF had a C–N amido bond, formed as a result of the reaction between the primary amines in the cashmere fibers and the carboxyl groups in the oxidized chitosan through the amide reaction. The OCGCF exhibited good moisture regain and remarkable bacteriostasis against both Staphylococcus aureus and Escherichia coli bacteria with its durability.

scholarly journals Charge Density Analysis and Transport Properties of TTF Based Molecular Nanowires: A DFT Approach

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Karuppannan Selvaraju ◽  
Poomani Kumaradhas
Keyword(s):  
Density Distribution ◽  
Charge Density ◽  
Electron Density ◽  
Quantum Chemical ◽  
Molecular Conformation ◽  
Topological Analysis ◽  
Basis Set ◽  
Bond Critical Point ◽  
Chemical Calculation ◽  
Energy Density Distribution

The present study has been performed to understand the charge density distribution and the electrical characteristics of Au and thiol substituted tetrathiafulvalene (TTF) based molecular nanowire. A quantum chemical calculation has been carried out using DFT method (B3LYP) with the LANL2DZ basis set under various applied electric fields (EFs). The bond topological analysis characterizes the terminal Au–S and S–C bonds as well as all the bonds of central TTF unit of the molecule. The variation of electron density and Laplacian of electron density at the bond critical point of bonds for zero and different applied fields reveal the electron density distribution of the molecule. The molecular conformation, the variation of atomic charges and energy density distribution of the molecule have been analyzed for the various levels of applied EFs. The HOMO-LUMO gap calculated from quantum chemical calculations has been compared with the value calculated from the density of states. The variation of dipole moment due to the polarization effect and the I-V characteristics of the molecule for the various applied EFs have been well discussed.

Synthesis of 24-phenyl-24-oxo steroids derived from bile acids by palladium-catalyzed cross coupling with phenylboronic acid. NMR characterization and X-ray structures

Steroids ◽  
2013 ◽  
Vol 78 (11) ◽  
pp. 1092-1097 ◽  
Author(s):  
Martha C. Mayorquín-Torres ◽  
Margarita Romero-Ávila ◽  
Marcos Flores-Álamo ◽  
Martin A. Iglesias-Arteaga
Keyword(s):  
Bile Acids ◽  
Phenylboronic Acid ◽  
Cross Coupling ◽  
X Ray ◽  
Nmr Characterization ◽  
Palladium Catalyzed

scholarly journals Revisiting the Thermodynamic Stability of Indomethacin Polymorphs with Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations

2018 ◽  
Author(s):  
Michael Ruggiero ◽  
Joshua J. Sutton ◽  
Sara J. Fraser-Miller ◽  
Adam J. Zaczek ◽  
Timothy M. Korter ◽  
...  
Keyword(s):  
Density Functional ◽  
Molecular Conformation ◽  
Low Frequency ◽  
Active Pharmaceutical Ingredient ◽  
Intermolecular Forces ◽  
State Density ◽  
Ab Initio Molecular Dynamics ◽  
Ambient Conditions ◽  
Molecular Dynamics Calculations ◽  
Vibrational Spectroscopies

<pre>The two major polymorphs of the active pharmaceutical ingredient indomethacin were studied using a combination of experimental low-frequency vibrational spectroscopies, theoretical solid-state density functional theory and \textit{ab initio} molecular dynamics calculations. The results enable a complete spectral assignment of the low-frequency IR and Raman spectra, and yield new insight into the energetic and dynamical factors present within the solids to be understood. Ultimately, these results are used to rationalize the thermodynamic properties of the two crystals, which result in a contradiction to the long-held belief that the $\gamma$-form is the more stable polymorph at ambient conditions due to its predominant abundance. Overall, the study highlights the combined role that molecular conformation, bulk packing arrangement, and intermolecular forces have on the ultimate properties of pharmaceutical crystals, and the need for detailed analyses into all of these effects in order to predict the properties of materials. </pre>

Synthesis of a doubly SO2-fused phlorin: Tuning the structure and properties by the SO2 groups

2018 ◽  
Vol 22 (09n10) ◽  
pp. 799-806
Author(s):  
Chengjie Li ◽  
Xiujun Liu ◽  
Jiewei Shao ◽  
Guangxian Su ◽  
Yongshu Xie
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectroscopy ◽  
Nmr Spectra ◽  
Molecular Conformation ◽  
Structure And Properties ◽  
X Ray ◽  
Ddq Oxidation

A doubly SO2-fused phlorin 4 has been synthesized by the [2 + 2] condensation of dipyrromethanecarbinol 2 and SO2-fused dipyrromenthane 3 in the presence of TFA, followed by DDQ oxidation. The SO2-fused phlorin 4 has been characterized by absorption, fluorescence, mass and NMR spectra, as well as X-ray analysis. Compared to the [Formula: see text]-unsubstituted phlorin 5, the SO2-fused phlorin 4 exhibits a red-shifted absorption spectrum (around 12 nm), a more distorted molecular conformation, as well as nice photostability even with an electron-donating meso-3,5-di-tert-butylphenyl group. The titration of 4 and 5 with TBAF has been monitored by absorption spectroscopy. The deprotonated phlorin 4 shows a peak at 870 nm which is red shifted by 26 nm compared to that of deprotonated 5.

Sign in / Sign up

Export Citation Format

Share Document