Double-bonded Oxygen Atom Research Articles

Pristine B40 fullerene as a potential gemcitabine drug carrier for anti-lung cancer properties: a DFT and QTAIM study

Novel biomedical applications of various nanomaterials are being extensively researched as drug delivery systems. These nanomaterials deliver various anticancer treatments into the specific tumor cell sites, which reduces their terrible side effects. In this study, we have used DFT/B3LYP/6-311++G(d,p) level of theory to examine the efficacy of the pristine B40 fullerene (Boron) as a drug delivery vehicle for gemcitabine an anti-lung cancer medication at various position. From our investigation the most stable adsorption orientation was observed between double bonded oxygen atom of the drug and six membered ring boron atoms of B40 fullerene both in gas and solvent phases. The frontier molecular orbitals and QTAIM studies further support the interaction of gemcitabine medication with the B40 fullerene. NBO and MEP methods show substantial charge transfer from gemcitabine drug molecules to the fullerene. Overall, the results suggest that the B40 fullerene effectively adsorbs the drug and hence can be used as a tool for drug delivery system.

Investigation of aluminum nitrate nanotube as the smart carriers for targeted delivery of gemcitabine anti-lung cancer drug

The potential of aluminum nitrate nanotube as a drug carrier for anti-lung cancer drug gemcitabine is examined based on the density functional theory (DFT) calculations. The adsorption geometries of gemcitabine drug onto the surface of nanotube are investigated for various orientation in order to attain the most stable configuration. Significant interaction is observed between the double bonded oxygen atom of the gemcitabine drug and aluminum atom of the nanocage. The charge transfer analysis indicates that there is significant interaction along with considerable charge transfer between gemcitabine and the aluminum nitrate nanotube. The electronic properties such as highest occupied molecular orbital, lowest unoccupied molecular orbitals energy levels, energy gap, chemical hardness, chemical potential, electrophilicity index, and dipole moment for the best three configurations of the complexation are examined. The recovery time calculations are also performed at 298.15 K temperature in order to study the drug desorption process on the targeted site. The stability of the complex is compared in both gas and aqueous medium. Eventually, this work interprets that aluminum nitrate nanotube can be considered to be suitable candidates for delivering gemcitabine anti-lung cancer drug in a biological system.

Nano- and microscale characterization for interfacial transition zone of geopolymer stabilized recycled aggregate of asphalt pavement

Geopolymer technology offers significant advantages in stabilizing recycled asphalt pavement (RAP), allowing its repurposing as road construction materials. This study employs a combination of molecular dynamics simulations and experimental characterization to investigate the properties of the interfacial transition zone (ITZ) in geopolymer-stabilized RAP. A composite model of geopolymer-aged asphalt-aggregate was established using molecular dynamics (MD) to access the effects of aging degrees of RAP on the interfacial bonding. The findings revealed that aging asphalt molecules on the RAP surface exhibit an affinity for Na+ present in geopolymers. Na+ ions migrate to the interfacial region, forming electrostatic interactions with double-bonded oxygen atoms in the aging asphalt molecules. The interfacial interaction energy and nanomechanical performance grow up and then reduced with the aging degree of RAP. SEM-EDS results verified these simulation findings, indicating that C(N)-A-S-H might grow at the interface, leading to a strong affinity and external chemical bonding.

Improved flotation of chalcopyrite from galena and pyrite by employing Cu-affinity phosphate collector

Sulfide minerals have similar flotation behavior using the commonly-used collectors such as xanthate due to its low selectivity to active metal ions on sulfide minerals, which leads to difficulties separating chalcopyrite from galena and pyrite. In this work, dibutyl phosphonate (HDBP) was investigated as a collector for chalcopyrite. Flotation tests confirmed that HDBP can selectively and effectively collect chalcopyrite at low concentrations and at environment-friendly pH. This was supported by the results of X-ray photoelectron spectrometry (XPS), electrochemical tests and Density Functional Theory (DFT) simulations. It can be inferred from the XPS results that single-bonded and double-bonded oxygen atoms in the HDBP structure undergo chemisorption with Cu atoms on the surface of chalcopyrite, while HDBP barely interacts with galena and pyrite. This was supported by the results of DFT simulations which showed that the stable adsorption of HDBP on the surface of chalcopyrite is formed by the four-member chelation ring with the P–O–Cu and P=O–Cu bonds with a higher adsorption energy of −133.01 kcal/mol. Electrochemical tests suggested that the corrosion potential and current of the chalcopyrite electrode increase significantly after using HDBP due to the formation of the new oxides. However, for galena and pyrite, there were no obvious changes, which further indicated that HDBP has a strong and selective reactivity to chalcopyrite. The strong affinity of HDBP for Cu atoms means that it has strong potential as a collector for the selective separation of copper-bearing minerals.

Boiling heat transfer of CO2/lubricant on structured surfaces using molecular dynamics simulations

In this paper, the molecular dynamics (MD) simulations are employed to investigate the effects of lubricant (PEC4) on the boiling heat transfer of CO2 on the structured surface. The results show that the structured surfaces can enhance the nucleation boiling of CO2 by providing effective bubble nucleation sites and larger heat transfer areas. However, with the increase of the mass fraction of PEC4, the nucleation boiling heat transfer efficiency decreases on the structured surface. The distribution characteristics of the CO2/PEC4 mixture during the boiling process show that parts of CO2 molecules in the liquid mixture are more likely to be adsorbed by the double-bonded oxygen atoms and carbon atoms of the ester groups of the PEC4 molecules, which hinders the movement and phase transition process of CO2 molecules. Therefore, the PEC4 molecules in the nucleation region first migrate to the top liquid region before bubble nucleation, and then bubble nuclei comes into being. When the mass fraction of PEC4 is higher than 7 wt%, the nucleation temperature is increased by 10 K to 20 K. The decrease of the CO2 nucleation boiling heat transfer performance caused by PEC4 istheconsequenceof thecoaction ofmanyfactors, including that the lubricant leads to a decrease in self-diffusion coefficient of CO2, an increase in liquid phase viscosity, an increase in bubble nucleation temperature of CO2, and a decrease in heat transfer resistance of the solid-liquid interface.

An atomic resolution description of folic acid using solid state NMR measurements.

The chemical shift anisotropy tensor and site-specific spin-lattice relaxation time of folic acid were determined by a 13C 2DPASS CP-MAS NMR experiment and Torchia CP experiment respectively. The molecular correlation time at various carbon nuclei sites of folic acid was evaluated by assuming that the 13C spin-lattice relaxation mechanism is mainly governed by chemical shift anisotropy interaction and hetero-nuclear dipole–dipole coupling. CSA parameters are larger for the carbon nuclei residing at the heteroaromatic ring and aromatic ring, and those attached to double-bonded electronegative oxygen atoms. It is comparatively low for C9, C19, C21, and C22. The molecular correlation time is of the order of 10−4/10−5 s for C9, C19, C21 and C22 carbon nuclei, whereas it is of the order of 10−3 s for the rest of the carbon nuclei sites. Spin lattice relaxation time varies from 416 s to 816 s. For C23 and C14, the value is 816 s, and it is 416 s for C7 nuclei. The correlation between structure and dynamics on an atomic scale of such an important drug as folic acid can be visualized by these types of extensive spectroscopic measurements, which will help to develop an advanced drug for DNA replication.

Vibrational and structural properties of P2O5 glass: Advances from a combined modeling approach

We present experimental measurements and ab initio simulations of the crystalline and amorphous phases of ${\mathrm{P}}_{2}{\mathrm{O}}_{5}$. The calculated Raman, infrared, and vibrational density of states (VDOS) spectra are in excellent agreement with experimental measurements and contain the signatures of all the peculiar local structures of the amorphous phase, namely, bridging and nonbridging (double-bonded or terminal) oxygens and tetrahedral ${\mathrm{PO}}_{4}$ units associated with ${Q}^{2}, {Q}^{3}$, and ${Q}^{4}$ species (${Q}^{n}$ denotes the various types of ${\mathrm{PO}}_{4}$ tetrahedra, with $n$ being the number of bridging oxygen atoms that connect the tetrahedra to the rest of the network). In order to reveal the internal structure of the vibrational spectrum, the characteristics of vibrational modes in different frequency ranges are investigated using a mode-projection approach at different symmetries based on the ${T}_{d}$ symmetry group. In particular, the VDOS spectrum in the range from $\ensuremath{\sim}600$ to 870 ${\mathrm{cm}}^{\ensuremath{-}1}$ is dominated by bending (${F}_{2b}$) motions related to bridging oxygen and phosphorus ($\ensuremath{\sim}800 {\mathrm{cm}}^{\ensuremath{-}1}$ band) atoms, while the high-frequency doublet zone ($\ensuremath{\sim}870$--1250 ${\mathrm{cm}}^{\ensuremath{-}1}$) is associated mostly with the asymmetric (${F}_{2s}$) and symmetric (${A}_{1}$) stretching modes, and most prominent peak around 1400 ${\mathrm{cm}}^{\ensuremath{-}1}$ (exp. 1380 ${\mathrm{cm}}^{\ensuremath{-}1}$) is mainly due to asymmetric stretching vibrations supported by double-bonded oxygen atoms. The lower-frequency range below 600 ${\mathrm{cm}}^{\ensuremath{-}1}$ is shown to arise from a mixture of bending ($E$ and ${F}_{2b}$) and rotation (${F}_{1}$) modes. The scissors bending ($E$) and rotation (${F}_{1}$) modes are well localized below 600 ${\mathrm{cm}}^{\ensuremath{-}1}$, whereas the ${F}_{2b}$ bending modes spread further into the range $\ensuremath{\sim}600$--870 ${\mathrm{cm}}^{\ensuremath{-}1}$. The projections of the eigenmodes onto ${Q}^{2}, {Q}^{3}$, and ${Q}^{4}$ species yield well-defined contributions at frequencies in striking correspondence with the positions of the Raman and infrared bands.

First-principles investigations on the contact electrification mechanism between metal and amorphous polymers for triboelectric nanogenerators

Chemical modification on contact pair materials is an important means to enhance the output of triboelectric nanogenerators (TENGs) as the electrification performance of contact materials depends critically on their molecular structures. However, limited understanding on the contact electrification mechanism between metal and amorphous polymer leads to the lack of theoretical basis on chemical modification ideas. On the basis of the typical amorphous polymers used in TENGs, polyethylene terephthalate (PET) and polyimide (Kapton), the method of first-principles research on amorphous polymers contact electrification is explored and the charge transfer mechanism between metal and amorphous polymer is studied. It is found that the electron acceptor in PET and Kapton is always the lowest unoccupied molecular orbital (LUMO) under different contact configurations and interface distances, which provides a clear direction for chemical modification on triboelectric materials. On the other hand, the major functional groups gaining electrons in PET and Kapton are found to be the carboxyl (-COOH) and the imide (-C(=O)NC(=O)-), respectively. Moreover, the contributions of double-bonded oxygen atoms in the carboxyl of PET and the imide of Kapton to contact electrification are significantly greater than that of single-bonded oxygen atoms in the carboxyl of PET and the ether of Kapton, respectively. This indicates that the contributions made by the same atomic species in different molecular groups to contact electrification are significantly different, which provides novel ideas for the chemical modification on triboelectric materials.

Superacidity of P(OH)3 and SO(OH)2 derivatives of cyclopentadiene and vinylcyclopentadiene in the gas phase: A computational DFT analysis

Strong Brønsted acids were designed using a simple strategy of replacing double-bonded oxygen atoms in mineral acids H3PO4 and H2SO4 with cyclopentadiene and vinylcyclopentadiene moieties, followed by a substitution with strong electron-withdrawing cyano groups. Their intrinsic gas-phase acidity was assessed by the B3LYP density functional theory calculations employing the 6-311++G(d,p) basis set, and many highly potent superacids were identified. The pronounced acidity of these conjugates is due to two predominant factors, namely, (i) an increase in the aromaticity of the five-membered ring on deprotonation, as evaluated through the NICS parameters, and (ii) an extension of the conjugated π-network enabled by the cyano groups that efficiently distribute an excess negative charge over a large number of atoms in conjugate bases. The SO(OH)2 derivatives are generally more acidic than the corresponding P(OH)3 counterparts so that the ΔHacid values for the SO(OH)2 and P(OH)3 derivatives with CN substituents evaluated here are 260-266 and 263-272 kcal mol−1, respectively. Given the growing interest in highly acidic molecules together with related acidic catalysts and metal complexing agents, the results presented here should direct the attention toward utilizing proposed systems as improved organic materials, and their synthesis is highly recommended.

DFT Studies on Interaction between Lanthanum and Hydroxyamide

Extraction and separation of individual rare earth elements has been a challenge as they are chemically very similar. Solvent extraction is the most suitable way for extraction of rare earth elements. Acidic, basic, neutral, chelating are the major classes of extractants for solvent extraction of rare earth elements. The coordination complex of chelating extractants is very selective with positively charged metal ion. Hence they are widely used. Hydroxyamide is capable of forming chelates with metal cations. In this present study interactions of hydroxyamide ligand with lanthanum have been investigated using density functional theory (DFT). Two different functional such as raB97XD and B3LYP are applied along with 6-31+G(d,p) basis set for carbon, nitrogen, hydrogen and SDD basis set for lanthanum. Stability of formed complexes has been evaluated based on calculated interaction energies and solvation energies. Frontier orbital (highest occupied molecular orbital or HOMO and lowest unoccupied molecular orbital or LUMO) energies of the molecule have also been calculated. Electronegativity, chemical hardness, chemical softness and chemical potential are also determined for these complexes to get an idea about the reactivity. From the partial charge distribution it is seen that oxygen atoms in hydroxyamide have higher negative charge. The double bonded oxygen atom present in the hydroxyamide structure has higher electron density and so it forms bond with lanthanum but the singly bonded oxygen atom in the hydroxyamide structure is weaker donor atom and so it is less available for interaction with lanthanum.

Interfacial Connection Mechanisms in Calcium-Silicate-Hydrates/Polymer Nanocomposites: A Molecular Dynamics Study.

Properties of organic/inorganic composites can be highly dependent on the interfacial connections. In this work, molecular dynamics, using pair-potential-based force fields, was employed to investigate the structure, dynamics, and stability of interfacial connections between calcium-silicate-hydrates (C-S-H) and organic functional groups of three different polymer species. The calculation results suggest that the affinity between C-S-H and polymers is influenced by the polarity of the functional groups and the diffusivity and aggregation tendency of the polymers. In the interfaces, the calcium counterions from C-S-H act as the coordination atoms in bridging the double-bonded oxygen atoms in the carboxyl groups (-COOH), and the Ca-O connection plays a dominant role in binding poly(acrylic acid) (PAA) due to the high bond strength defined by time-correlated function. The defective calcium-silicate chains provide significant numbers of nonbridging oxygen sites to accept H-bonds from -COOH groups. As compared with PAA, the interfacial interactions are much weaker between C-S-H and poly(vinyl alcohol) (PVA) or poly(ethylene glycol) (PEG). Predominate percentage of the -OH groups in the PVA form H-bonds with inter- and intramolecule, which results in the polymer intertwining and reduces the probability of H-bond connections between PVA and C-S-H. On the other hand, the inert functional groups (C-O-C) in poly(ethylene glycol) (PEG) make this polymer exhibit unfolded configurations and move freely with little restrictions. The interaction mechanisms interpreted in this organic-inorganic interface can give fundamental insights into the polymer modification of C-S-H and further implications to improving cement-based materials from the genetic level.

Ground state structure of high-energy-density polymeric carbon monoxide

Crystal structure prediction methods and first-principles calculations have been used to explore low-energy structures of carbon monoxide (CO). Contrary to the standard wisdom, the most stable structure of CO at ambient pressure was found to be a polymeric structure of $Pna{2}_{1}$ symmetry rather than a molecular solid. This phase is formed from six-membered (four carbon + two oxygen) rings connected by C=C double bonds with two double-bonded oxygen atoms attached to each ring. Interestingly, the polymeric $Pna{2}_{1}$ phase of CO has a much higher energy density than trinitrotoluene (TNT). On compression to about 7 GPa, $Pna{2}_{1}$ is found to transform into another chainlike phase of $Cc$ symmetry which has similar ring units to $Pna{2}_{1}$. On compression to 12 GPa, it is energetically favorable for CO to polymerize into a purely single bonded $Cmca$ phase, which is stable over a wide pressure range and transforms into the previously known $Cmcm$ phase at around 100 GPa. Thermodynamic stability of these structures was verified using calculations with different density functionals, including hybrid and van der Waals corrected functionals.

Molecular Dynamics Simulation of Methane Hydrate Growth in the Presence of the Natural Product Pectin

Molecular dynamics simulation was used to examine the growth of methane hydrate in the presence of natural product pectin at different concentrations, including the mass fractions 2.46% and 3.62%. Snapshots of the system configurations with time, radial distribution functions of the carbon atoms, and the total energy of the system were employed to characterize the effect of pectin on methane hydrate growth. Results indicated that pectin is a good inhibitor of methane hydrate. The higher the concentration of pectin is, the better the effect of inhibition is. The double-bonded oxygen atoms of pectin combine with hydrogen atoms of water, and the hydrogen atoms of hydroxyl in pectin combine with oxygen atoms of water through hydrogen bonds, which disturbed the further growth of the methane hydrate. The role of the pectin’s active groups in hydrogen bonds with water both as proton donor and as electron acceptor makes pectin have a better inhibitory effect on the growth of methane hydrate.

DFT studies of the interactions between the [Ca(H2O)5]2+ cation and monofunctional oxo, aza, sulfur and phosphorous ligands

Quantum chemical calculations using the B3LYP/6-311++G(d,p) method were performed to determine the affinity of the [Ca(H2O)5]2+ cation for several monofunctional ligands. Four sets of ligands were studied: with oxygen binding atom (phosphoryl, amide, carboxylic acid, ketone, aldehyde, ether, alcohol, enol), nitrogen (imine, thiocyanic acid, nitrile, amine and ammonia), sulfur (thiocarbonyl, thioether and thioalcohol) and phosphorous (phosphine) binding atom. Compounds that bind via a double bonded oxygen atom have the strongest metal–ligand interaction, followed by compounds binding via nitrogen, singly bonded oxygen atom, sulfur and phosphine. The ligand with the strongest interaction, phosphine oxide, has an ionic resonance form with a negative charge on the binding oxygen atom that highly contributes to the hybrid geometry, what favors the interaction. The Energy Decomposition Analysis (EDA) of the interaction energy between the [Ca(H2O)5]2+ cation and the ligand shows that the electrostatic term is the major component of the interaction and represents at least 43.66% of the total interaction energy. The covalent component represents at least 28.09% of the total interaction energy. Along the set of compounds studied, the electrostatic component varies more than twice the covalent term. The repulsive and the dispersion components are roughly constant in all complexes.

Solubility of Carbon Dioxide in Pentaerythritol Hexanoate: Molecular Dynamics Simulation of a Refrigerant-Lubricant Oil System.

We have investigated the solubility and the solvation structure between a refrigerant (carbon dioxide, CO2) and a lubricant oil (pentaerythritol hexanoate, PEC6) by molecular dynamics simulations. First, to investigate the solubility, we calculated the vapor-liquid equilibrium pressure. The chemical potential of the liquid phase and the gas phase were calculated, and the equilibrium state was obtained from the crossing point of these chemical potentials. The equilibrium pressures agreed well with experimental data over a wide range of temperatures and mole fractions of CO2. Second, the solvation structure was also investigated on a molecular scale. We found the following characteristics. First, the tails of the lubricant oil are relatively rigid inside the ester groups but flexible beyond. Second, CO2 molecules barely enter the lubricant core as delimited by the ester groups. Third, the double-bonded oxygen atoms of the ester groups are good sorption sites for CO2. Fourth, only a few CO2 molecules are attached to more than one carbonyl oxygen simultaneously. Finally, there is also significant unspecific sorption of CO2 in the alkane tail region. These results indicate that increasing the size of the rigid lubricant core would probably decrease the solubility, whereas increasing the number of polar groups would increase it.

Charge density analysis of paracetamol, acetotoluidine and methacetin

Paracetamol (p-hydroxyacetanilide, Pbca), acetotoluidine (p-methylacetanilide, P21/c) and methacetin (p-methoxyacetanilide, Pbca) contain acetamide group included in molecular fragments, which play an important role in many drugs and proteins. As all of them are derivatives of acetanilide used in medicine, and due to the presence of the amide bond, their charge density analysis is important for better understanding amide infinite peptide chains. Thus, comparing the data obtained for paracetamol with acetotoluidine and with methacetin charge density data can provide deeper insight into NH···O bonding. Another point of interest is the possibility of methyl group rotation that remains to be ambiguous in these acetanilide molecule based compounds. In the present study we have attempted to elucidate these problems using precise X-ray diffraction at 100K with subsequent charge density topological analysis. All charge density refinements were based on the Hansen and Coppens multipolar atom model. The topologies of the inter- and intramolecular interactions are carefully analyzed for compounds. The atomic charges, bond orders, and the electrostatic energy in molecules are discussed. The topological characteristics in the critical point of the NH···O bond of paracetamol, acetotoluidine and methacetin are shown in the table below. In contrast to similarity in NH···O bonds for all studied compounds, intermolecular interactions between the double bonded oxygen atom and the hydrogen of dimer's methyl group are different. In acetotoluidine and methacetin the (3, –1) critical points with the same topological characteristics were detected between these atoms. In comparison to them, paracetamol with disordered methyl group [1, 2] has no such point. That can be related to the absence of the methyl group disorder in acetotoluidine and methacetin.

Exciting hot carrier to a high energy state by impact excitation in low density nanocrystalline Si films

The carrier recombination processes in low density nanocrystalline (nc-) Si films have been studied by steady and time-resolved photoluminescence (PL) spectra, and the hot carriers have been excited to a high energy state by impact excitation. A yellow-green PL band locating at 580nm appears when the studied film is excited by two optical beams. The yellow-green PL band results from band-to-band transition in Si nanocrystals with double-bonded oxygen atoms, which is caused by impact excitation among the carriers in the nc-Si film. The decay time of the yellow-green PL band is 230ns, which is much longer than the hot carrier cooling. The results indicate that the lost energy in the solar cell may be collected from the new recombination center in the further structural design.

Piperidone synthesis using amino acid: A promising scope for green chemistry

Piperidone is a family of organic chemicals characterized by a 6-carbon ring substituted with nitrogen and a double-bonded oxygen atom. Piperidones are named by the location of the nitrogen or amine group on the ring. It differs from piperidine by the presence of oxygen molecule (from ketone). It is used in pharmaceutical companies and chemical manufacturers as intermediates having anti microbial activity. It is usually synthesized using ammonia both in laboratory and industry. In present study, amino acid namely aspartic acid is used instead of ammonia. The amino acid incorporated piperidones is purified and analyzed using NMR spectroscopy. It has antimicrobial activity against Pseudomonas aeruginosa and Salmonella aboni.

NMR Study of the [VO(O2)2F]2‐ Ion in Solution: Synthesis, Vibrational Spectra and Crystal Structure of [NH3CH2CH2NH3] [VO(O2)2F

AbstractFor Abstract see ChemInform Abstract in Full Text.

NMR study of the [VO(O 2) 2F] 2− ion in solution: Synthesis, vibrational spectra and crystal structure of [NH 3CH 2CH 2NH 3][VO(O 2) 2F

The presence of the [VO(O 2) 2F] 2− ion in an aqueous solution gives rise to a doublet ( δ = −714 ppm, J VF = 163 ± 3 Hz) in the 51V NMR, and a multiplet ( δ = −160 ppm, Δ ν 1/2 = 1163 Hz) in the 19F NMR spectrum. The formation of this species is enhanced in formamide solutions. The ethane-1,2-diammonium(2+) fluorooxodiperoxovanadate, [NH 3CH 2CH 2NH 3][VO(O 2) 2F], was prepared from aqueous solution and characterized by elemental analysis, and IR and Raman spectroscopies. The complex crystallizes in the orthorhombic space group Pbca with eight formula units in a cell of dimensions: a = 9.2690(4), b = 8.8321(5) and c = 16.7605(8) Å. The complex anion has a rare pentagonal pyramidal structure with a very weak intermolecular interaction d(V ⋯ O) = 2.8730(12) Å between the vanadium atom and the double-bonded oxygen atom from the adjacent anion.