scholarly journals Crystalline Peroxosolvates: Nature of the Coformer, Hydrogen-Bonded Networks and Clusters, Intermolecular Interactions

Molecules ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 26
Author(s):  
Alexander G. Medvedev ◽  
Andrei V. Churakov ◽  
Petr V. Prikhodchenko ◽  
Ovadia Lev ◽  
Mikhail V. Vener
Keyword(s):  
Density Functional ◽  
High Energy ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Functional Theory ◽  
Sodium Percarbonate ◽  
Analgesic Effects ◽  
1D Chain ◽  
The Stability ◽  
Insight Into

Despite the technological importance of urea perhydrate (percarbamide) and sodium percarbonate, and the growing technological attention to solid forms of peroxide, fewer than 45 peroxosolvates were known by 2000. However, recent advances in X-ray diffractometers more than tripled the number of structurally characterized peroxosolvates over the last 20 years, and even more so, allowed energetic interpretation and gleaning deeper insight into peroxosolvate stability. To date, 134 crystalline peroxosolvates have been structurally resolved providing sufficient insight to justify a first review article on the subject. In the first chapter of the review, a comprehensive analysis of the structural databases is carried out revealing the nature of the co-former in crystalline peroxosolvates. In the majority of cases, the coformers can be classified into three groups: (1) salts of inorganic and carboxylic acids; (2) amino acids, peptides, and related zwitterions; and (3) molecular compounds with a lone electron pair on nitrogen and/or oxygen atoms. The second chapter of the review is devoted to H-bonding in peroxosolvates. The database search and energy statistics revealed the importance of intermolecular hydrogen bonds (H-bonds) which play a structure-directing role in the considered crystals. H2O2 always forms two H-bonds as a proton donor, the energy of which is higher than the energy of analogous H-bonds existing in isostructural crystalline hydrates. This phenomenon is due to the higher acidity of H2O2 compared to water and the conformational mobility of H2O2. The dihedral angle H-O-O-H varies from 20 to 180° in crystalline peroxosolvates. As a result, infinite H-bonded 1D chain clusters are formed, consisting of H2O2 molecules, H2O2 and water molecules, and H2O2 and halogen anions. H2O2 can form up to four H-bonds as a proton acceptor. The third chapter of the review is devoted to energetic computations and in particular density functional theory with periodic boundary conditions. The approaches are considered in detail, allowing one to obtain the H-bond energies in crystals. DFT computations provide deeper insight into the stability of peroxosolvates and explain why percarbamide and sodium percarbonate are stable to H2O2/H2O isomorphic transformations. The review ends with a description of the main modern trends in the synthesis of crystalline peroxosolvates, in particular, the production of peroxosolvates of high-energy compounds and mixed pharmaceutical forms with antiseptic and analgesic effects.

Mechanistic Insights into Protonated Diamines-catalyzed Decarboxylation of Oxaloacetate

2019 ◽  
Vol 16 (3) ◽  
pp. 202-208
Author(s):  
Chuangang Fan ◽  
Mingzhi Song
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Density Functional ◽  
Catalytic Mechanism ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Chemical Mechanisms ◽  
Insight Into

The chemical mechanisms of protonated diamines-catalyzed decarboxylation of oxaloacetic acid anions in water solutions have been studied by using density functional theory. The calculated results show that the activated Gibbs free energy of the decarboxylation step is the highest in the whole diamine-catalytic processes for OA2-, and protonated ethylenediamine (ENH+) is the best catalyst of the five diamines, which is consistent with the study of Thalji et al. However, for OA-, different with OA2-, the dehydration step is the rate-determining one except 1,3-diaminopropane, and protonated 1,4- diaminobutane is the best catalyst of the five catalysts. The results also indicate that the second amino group participates in the reaction as the proton acceptor or proton donor, and it assists in decarboxylation by hydrogen bonds, decreasing the active Gibbs free energy barrier of the whole catalytic process. These results provide insight into the precise catalytic mechanism of several enzymes whose reactions are known to proceed via an imine intermediate.

scholarly journals New Rod-Like H-Bonded Assembly Systems: Mesomorphic and Geometrical Aspects

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 795
Author(s):  
Laila A. Al-Mutabagani ◽  
Latifah Abdullah Alshabanah ◽  
Hoda A. Ahmed ◽  
Khulood A. Abu Al-Ola ◽  
Mohamed Hagar
Keyword(s):  
Density Functional ◽  
Polarized Light ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Scanning Calorimetry ◽  
Functional Theory ◽  
Ft Ir ◽  
Ir Spectroscopic ◽  
Thermal Stability Of ◽  
Bonded Complexes

Experimental and geometrical approaches of new systems of mesomorphic 1:1 supramolecular H-bonded complexes (SMHBCs) of five rings are discussed. The H-bonding between 4-alkoxyphenylimino benzoic acids (An, as proton acceptor) and 4-(4′–pyridylazophenyl) 4′′-alkoxybenzoates (Bm, as proton donor) were investigated. Mesomorphic behaviors were analyzed by differential scanning calorimetry (DSC) and mesophase textures were identified by polarized light microscopy (POM). H-bonded assembly was established by FT-IR spectroscopic measurements via Fermi band discussion. Thermal and theoretical factors were predicted for all synthesized complexes by density functional theory (DFT) predictions. The results revealed that all prepared complexes were monomorphic, with a broad range of smectic A phases with a high thermal stability of enantiotropic mesophase. Furthermore, DFT stimulations illustrated the experimental results in terms of the influence of the chain length either of the acid or the base component. Many parameters, such as the calculated stability, the dipole moment and the polarizability of the H-bonded complexes, illustrate how these parameters work together to enhance the smectic mesophases with the obtained stability and range.

A theoretical study of 3,5-diazido-1,2,4-triazole: the role of the hydrogen bonding interaction in stabilizing the molecular system

2014 ◽  
Vol 92 (9) ◽  
pp. 896-903 ◽  
Author(s):  
Junqing Yang ◽  
Xuedong Gong ◽  
Guixiang Wang
Keyword(s):  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Density Functional ◽  
Molecular System ◽  
Polarizable Continuum Model ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Good Thermal Stability ◽  
The Stability ◽  
Dynamics Simulations

3,5-Diazido-1, 2, 4-triazole (DATZ) is a compound that has a good thermal stability and can be used to produce high energetic ionic salts. The conformations of DATZ were searched by the molecular dynamics simulations and optimized by the molecular mechanics and dispersion-corrected density functional theory methods. The dimer and trimer of DATZ were constructed from the most stable monomer. The hydrogen bonding interactions, which were found to be critically important in increasing the stability of the dimer and trimer, were investigated with the help of the natural bond orbital and the quantum theory of atoms in molecules analyses. The changes in thermodynamic functions, stabilization interaction energies, and hydrogen-bonding energies show that the trimer is most likely the existing form of DATZ. The intramolecular, intermolecular, and water catalytic proton transfer processes were simulated to investigate the proton transfer mechanism. The intermolecular transfer process requires the lowest activation energy (42.56 kJ mol−1) and is the most likely process of proton transfer. DATZ is not only a proton acceptor but also a proton donor. Its weak acidity was quantified as pKa = 10.16. The solvation energy estimated using the conductor-like polarizable continuum model in water is the largest (−99.96 kJ mol−1), revealing that DATZ is more stable in water than in another seven solvents.

Theoretical study on six-fold coordinated silicon in silicophosphate compounds

2006 ◽  
Vol 84 (8) ◽  
pp. 1024-1030 ◽  
Author(s):  
Hassan Rabaâ ◽  
Fatima Bkiri
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
High Energy ◽  
Functional Theory ◽  
Model Cluster ◽  
Hartree Fock ◽  
Ir Frequencies ◽  
The Stability ◽  
Remarkable Agreement ◽  
Cluster 2

Extended Hückel tight-binding (EHTB) calculations were performed on silicophosphate compounds with six-coordinated silicon. Speculative structures related to silicon coordination in SiP2O7 are reported. To account for the particular structural distortion caused by the presence of SiO6 in the silicon pyrophosphate, it is important to examine how the stability and the band gap of the extended structure of SiP2O7 are affected. Different theoretical tools are used (EHTB, ab initio Hartree–Fock, and density functional theory DFT-B3LYP). To obtain detailed descriptions of the incorporation of hexacoordinated silicon in this material, the band structures in SiP2O7 and [P2O7]4– were analyzed. It seems that the diffuse orbitals of silicon and the high energy of the Si 3p orbital lead to higher energy coordination and contribute to the breaking of the P-O-P bridge and the forming of a Si-O-P entity in this material. In addition, to provide more evidence of the existence of the octahedral silicon coordination in SiP2O7 (1), two model clusters [P4Si2O23H18] (2) and [P4Si2O19H10] (3) involving silicon atoms in octahedral and tetrahedral sites were investigated using Hartree–Fock and DFT theories. A remarkable agreement between calculated and experimental bond lengths for Si—O and P—O is obtained using the DFT calculation. The model cluster 2 corroborates the structural change in the Si-O-P and P-O-P fragments seen in 1. The IR vibrational frequencies are calculated for both model clusters and are predicted to shift towards lower frequencies in the octahedral Si sites, which is consistent with experimental data.Key words: silicophosphate, SiO6, band structure, tight-binding calculations, Hartree-Fock, DFT, B3LYP, model cluster, IR frequencies.

scholarly journals Computational Investigation and Screening of High-Energy-Density Materials: Based on Nitrogen-Rich 1,2,4,5-tetrazine Energetic Derivatives

2021 ◽  
Author(s):  
Lian Zeng ◽  
Yuhe Jiang ◽  
Jinting Wu ◽  
Hongbo Li ◽  
Jianguo Zhang
Keyword(s):  
Enthalpy Of Formation ◽  
Density Functional ◽  
High Energy ◽  
High Energy Density ◽  
Detonation Performance ◽  
Detonation Properties ◽  
Functional Theory ◽  
High Energy Density Materials ◽  
The Stability ◽  
The Enthalpy Of Formation

Abstract: In the present work, the geometric structures, the frontier molecular orbitals and the enthalpy of formation (HOF) of thirty six 1, 2, 4, 5-tetrazine derivatives (FTT) were systematically studied by using the B3LYP/6-311+G* method of density functional theory. Meanwhile, we also predicted the stability, detonation properties and thermodynamic properties of all FTT compounds. Results showed that all compounds have superior enthalpy of formation far exceeding that of common explosives RDX and HMX, ranging from 859kJ·mol-1-1532kJ·mol-1. In addition, the detonation performance (Q = 1426cal·g-1 -1804cal·g-1; P = 29.54GPa - 41.84GPa; D = 8.02km·s-1 - 9.53km·s-1), which is superior to TATB and TNT. It is also concluded that the introduction of coordination oxygen on the tetrazine ring can improve the HOF, density and detonation performance of the title compound, and -NH-NH- bridge and -NHNO2 group are also the perfect combination to increase these values. In view of stability, because of the fascinating performance of D3 (ρ =1.89g·cm-3; D = 9.38km·s-1; P = 40.13GPa)，E3(ρ = 1.87g·cm-3; D = 9.19km·s-1; P = 38.35GPa), F1 (ρ = 1.87g·cm-3; D = 9.42km·s-1; P = 40.23GPa) and F3 (ρ= 1.92g·cm-3; D = 9.53km·s-1; P = 41.84GPa), makes them very attractive to be chosen as HEDMs.

Effect of the alloying element titanium on the stability and trapping of hydrogen in pure vanadium: A first-principles study

2014 ◽  
Vol 28 (29) ◽  
pp. 1450207 ◽  
Author(s):  
Juan Hua ◽  
Yue-Lin Liu ◽  
Heng-Shuai Li ◽  
Ming-Wen Zhao ◽  
Xiang-Dong Liu
Keyword(s):  
Binary Alloy ◽  
First Principles ◽  
Density Functional ◽  
Interstitial Site ◽  
Alloying Element ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Tetrahedral Interstitial Site ◽  
The Stability ◽  
Insight Into

With a first-principles method based on density functional theory, the effect of the alloying element titanium ( Ti ) on the thermodynamic stability and electronic structure of hydrogen ( H ) in pure vanadium ( V ) is investigated. The interactions between H and the vacancy and the defect solution energies in a dilute V – Ti binary alloy are calculated. The results show that: (i) a single H atom prefers to reside in a tetrahedral interstitial site in dilute V – Ti binary alloy systems; (ii) H atoms tend to bond at the vacancy sites; a mono-vacancy is shown to be capable of trapping three H atoms; and (iii) the presence of Ti in pure V can increase the H trapping energy and reduce the H trapping capability of the vacancy defects. This indicates that doping with Ti to form dilute V – Ti binary alloys can inhibit the solution for H , and thus suppress the retention of H . These results provide useful insight into V -based alloys as a candidate structural material in fusion reactors.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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