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1.
The constant-volume combustion energy, △cU (DADE, s, 298.15 K), the thermal behavior, and kinetics and mechanism of the exothermic decomposition reaction of 1,1-diamino-2,2-dinitroethylene (DADE) have been investigated by a precise rotating bomb calorimeter, TG-DTG, DSC, rapid-scan fourier transform infrared (RSFT-IR) spectroscopy and T-jump/FTIR, respectively. The value of △cHm (DADE, s, 298.15 K) was determined as (-8518.09±4.59) j·g^-1. Its standard enthalpy of combustion, △cU (DADE, s, 298.15 K), and standard enthalpy of formation, △fHm (DADE, s, 298.15 K) were calculated to be (-1254.00±0.68) and (- 103.98±0.73) kJ·mol^-1, respectively The kinetic parameters (the apparent activation energy Ea and pre-exponential factor A) of the first exothermic decomposition reaction in a temperature-programmed mode obtained by Kissinger's method and Ozawa's method, were Ek=344.35 kJ·mol^-1, AR= 1034.50 S^-1 and Eo=335.32 kJ·mol^-1, respectively. The critical temperatures of thermal explosion of DADE were 206.98 and 207.08 ℃ by different methods. Information was obtained on its thermolysis detected by RSFT-IR and T-jump/FTIR.  相似文献   

2.
Nitrogen‐rich heterocyclic bases and oxygen‐rich acids react to produce energetic salts with potential application in the field of composite explosives and propellants. In this study, 12 salts formed by the reaction of the bases 4‐amino‐1,2,4‐trizole (A), 1‐amino‐1,2,4‐trizole (B), and 5‐aminotetrazole (C), upon reaction with the acids HNO3 (I), HN(NO2)2 (II), HClO4 (III), and HC(NO2)3 (IV), are studied using DFT calculations at the B97‐D/6‐311++G** level of theory. For the reactions with the same base, those of HClO4 are the most exothermic and spontaneous, and the most negative ΔrGm in the formation reaction also corresponds to the highest decomposition temperature of the resulting salt. The ability of anions and cations to form hydrogen bonds decreases in the order NO3?>N(NO2)2?>ClO4?>C(NO2)3?, and C+>B+>A+. In particular, those different cation abilities are mainly due to their different conformations and charge distributions. For the salts with the same anion, the larger total hydrogen‐bond energy (EH,tot) leads to a higher melting point. The order of cations and anions on charge transfer (q), second‐order perturbation energy (E2), and binding energy (Eb) are the same to that of EH,tot, so larger q leads to larger E2, Eb, and EH,tot. All salts have similar frontier orbitals distributions, and their HOMO and LUMO are derived from the anion and the cation, respectively. The molecular orbital shapes are kept as the ions form a salt. To produce energetic salts, 5‐aminotetrazole and HClO4 are the preferred base and acid, respectively.  相似文献   

3.
Ab initio calculations at the unrestricted Hartree–Fock (UHF) level have been performed to investigate the hydrogen abstraction reactions of ? OH radicals with methane and nine halogen‐substituted methanes (F, Cl). Geometry optimization and vibrational frequency calculations have been performed on all reactants, adducts, products, and transition states at the UHF/6‐31G* level. Single‐point energy calculations at the MP2/6‐31++G* level using the UHF/6‐31G* optimized geometries have also been carried out on all species. Pre‐ and postreaction adducts have been detected on the UHF/6‐31G* potential energy surfaces of the studied reactions. Energy barriers, ΔE?, reaction energies, ΔEr, reaction enthalpies, ΔHr, and activation energies, Ea, have been determined for all reactions and corrected for zero‐point energy effects. Both Ea and ΔHr come into reasonable agreement with the experiment when correlation energy is taken into account and when more polarized and diffuse basis sets are used. The Ea values, estimated at the PMP2/6‐31++G* level, are found to be in good agreement with the experimental ones and correctly reproduce the experimentally observed trends in fluorine and chlorine substitution effects. A linear correlation between Ea and ΔHr is obtained, suggesting the presence of an Evans–Polanyi type of relationship. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 426–440, 2001  相似文献   

4.
The adsorption of six electron donor–acceptor (D/A) organic molecules on various sizes of graphene nanoflakes (GNFs) containing two common defects, double‐vacancy (5‐8‐5) and Stone–Wales (55‐77), are investigated by means of ab initio DFT [M06‐2X(‐D3)/cc‐pVDZ]. Different D/A molecules adsorb on a defect graphene (DG) surface with binding energies (ΔEb) of about ?12 to ?28 kcal mol?1. The ΔEb values for adsorption of molecules on the Stone–Wales GNF surface are higher than those on the double vacancy GNF surface. Moreover, binding energies increase by about 10 % with an increase in surface size. The nature of cooperative weak interactions is analyzed based on quantum theory of atoms in molecules, noncovalent interactions plot, and natural bond order analyses, and the dominant interaction is compared for different molecules. Electron density population analysis is used to explain the n‐ and p‐type character of defect graphene nanoflakes (DGNFs) and also the change in electronic properties and reactivity parameters of DGNFs upon adsorption of different molecules and with increasing DGNF size. Results indicate that the HOMO–LUMO energy gap (Eg) of DGNFs decreases upon adsorption of molecules. However, by increasing the size of DGNFs, the Eg and chemical hardness of all complexes decrease and the electrophilicity index increases. Furthermore, the values of the chemical potential of acceptor–DGNF complexes decrease with increasing size, whereas those of donor–DGNF complexes increase.  相似文献   

5.
We have studied the structure and geometry of neutral and charged atomic clusters consisting of Ga and As atoms via ab initio Hartree–Fock (HF) and second‐order Møller–Plesset methods. The GamAsn cluster with mn composition prefers a nontetrahedral geometry in the charge neutral (q=0) state. These clusters tend to be stable in tetrahedral geometry when appropriately charged. The GamAsn cluster with m=n composition (1:1 ratio of Ga to As atoms) tends to be stable in a tetrahedral geometry in the charge neutral (q=0) state. With increasing size of the cluster, the geometry of GanAsn cluster approaches the zinc‐belende‐type crystalline structure. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 563–573, 2000  相似文献   

6.
We report the time‐resolved supramolecular assembly of a series of nanoscale polyoxometalate clusters (from the same one‐pot reaction) of the form: [H(10+m)Ag18Cl(Te3W38O134)2]n, where n=1 and m=0 for compound 1 (after 4 days), n=2 and m=3 for compound 2 (after 10 days), and n=∞ and m=5 for compound 3 (after 14 days). The reaction is based upon the self‐organization of two {Te3W38} units around a single chloride template and the formation of a {Ag12} cluster, giving a {Ag12}‐in‐{W76} cluster‐in‐cluster in compound 1 , which further aggregates to cluster compounds 2 and 3 by supramolecular Ag‐POM interactions. The proposed mechanism for the formation of the clusters has been studied by ESI‐MS. Further, control experiments demonstrate the crucial role that TeO32?, Cl?, and Ag+ play in the self‐assembly of compounds 1 – 3 .  相似文献   

7.
X‐ray fluorescence measurements for O‐containing [polyethylene oxide, polyvinyl alcohol, polyvinyl methyl ether], CO‐containing [polyvinyl methyl ketone, polyethylene terephthalate], N‐containing [poly‐4‐vinylpyridine (P4VP), polyaniline oligomer (PAO)], and S‐containing [polyphenylene sulfide] substances are presented. Carbon Kα X‐ray emission spectra (XES) and X‐ray photoelectron spectra (XPS) are compared with our DFT calculations performed with the Amsterdam density functional (ADF) program. The combined analysis of valence XPS and carbon Kα XES allows us to determine the individual contributions from pσ‐ and pπ‐bonding molecular orbitals of the polymers. The ΔSCF calculations yield the accurate C1s core‐electron binding energies (CEBEs) for all carbon sites of the organic compound. We calculate all CEBEs of the model molecules using the ΔE KS approach. Our simulated C1s photoelectron and C Kα emission spectra are in good agreement with our measurements. We also obtain WD (work function and the other energies) values for the polymers and PAO from the difference between calculated (gas‐phase) and measured (solid) CEBE values. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 162–172, 2007  相似文献   

8.
A series of polystyrene‐block‐poly(polyethylene glycol monomethyl ether acrylate) (PStmb‐PPEGAn) polymers were systematically synthesized as carriers for zinc phthalocyanine (ZnPc) for photodynamic therapy via reversible addition and fragmentation chain transfer polymerization. The degree of polymerization of the styrene (m) and PEGA units (n) of the resulting block copolymers were characterized to be n = 174, 40, and 18 for m = 52; and n = 200, 84, and 31 for m = 30. All the block copolymers formed micelles in water. The critical micelle concentration (CMC) of the PStmb‐PPEGAn was determined by fluorometry using pyrene as a hydrophobic probe. The CMC value increased from 4.5 to 20 mg·L−1 with an increase in the mole fraction of PEGA units. The median diameters of the micelles increased from 19 to 31 nm for PSt52b‐PPEGAn and from 15 to 23 nm for PSt30b‐PPEGAn with increasing n value. ZnPc‐loaded micelles were prepared by dialysis of the block copolymer in the presence of ZnPc followed by removal of large aggregates by filtration. The encapsulation efficiency was dramatically changed in the range of 0–68%. The light‐dose‐dependent cytotoxicity of the ZnPc‐loaded PSt30b‐PPEGA200 was clearly established in HeLa cell lines; while no cytotoxicity was confirmed under the dark. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 560–570  相似文献   

9.
Electrospray ionization mass spectrometry (ESI‐MS) is an analytical technique that measures the mass of a sample through “soft” ionization. Recent years have witnessed a rapid growth of its application in noble‐metal nanocluster (NC) analysis. ESI‐MS is able to provide the mass of a noble‐metal NC analyte for the analysis of their composition (n, m, q values in a general formula [MnLm]q), which is crucial in understanding their properties. This review attempts to present various developed techniques for the determination of the composition of noble metal NCs by ESI‐MS. Additionally, advanced applications that use ESI‐MS to further understand the reaction mechanism, complexation behavior, and structure of noble metal NCs are introduced. From the comprehensive applications of ESI‐MS on noble‐metal NCs, more possibilities in nanochemistry can be opened up by this powerful technique.  相似文献   

10.
We investigated the structural principles of novel germanium modifications derived by oxidative coupling of Zintl‐type [Ge9]4?clusters in various ways. The structures, stabilities, and electronic properties of the predicted {2[Ge9]n} sheet, {1[Ge9]n} nanotubes, and fullerene‐like {Ge9}n cages were studied by using quantum chemical methods. The polyhedral {Ge9}n cages are energetically comparable with bulk‐like nanostructures of the same size, in good agreement with previous experimental findings. Three‐dimensional structures derived from the structures of lower dimensionality are expected to shed light on the structural characteristics of the existing mesoporous Ge materials that possess promising optoelectronic properties. Furthermore, 3D networks derived from the polyhedral {Ge9}n cages lead to structures that are closely related to the well‐known LTA zeolite framework, suggesting further possibilities for deriving novel mesoporous modifications of germanium. Raman and IR spectra and simulated X‐ray diffraction patterns of the predicted materials are given to facilitate comparisons with experimental results. The studied novel germanium modifications are semiconducting, and several structure types possess noticeably larger band gaps than bulk α‐Ge.  相似文献   

11.
Adsorption of pyridine on Nin‐clusters (with n = 2,3,4) is studied by quantum chemical calculations at B3LYP/LANL2DZ and B3LYP/6‐311G** levels. First, Nin‐clusters are investigated for accessible structure and electronic states. The lowest electronic state with four unpaired electrons is predicted for Ni4‐cluster based on geometry and electronic structure, showing that the cluster stability nicely depends on number of unpaired electrons. Correction for basis set superposition error of metal‐metal bond is appreciable and has increasing effect on cluster binding energy. Next, adsorption of pyridine in planar and vertical adsorption modes is investigated on rhombus Ni4‐cluster. The vertical mode is found (at B3LYP/6‐311G** level) as the most favorable adsorption mode. Adsorption energy (ΔEads) depends on cluster size; adsorption on Ni4‐cluster is most favorable with ΔEads = ?207.33 kJ/mol. The natural bond orbital analysis reveals the charge transfer in adsorbate/metal‐cluster. Results of investigations for the Ni2‐ and Ni3‐cluster are also presented. © 2012 Wiley Periodicals, Inc.  相似文献   

12.
A series of novel heterochelates of the type [Fe(An)(L)(H2O)2]?mH2O [where H2An = 4,4′‐(arylmethylene)bis(3‐methyl‐1‐phenyl‐4,5‐dihydro‐1H‐pyrazol‐5‐ol); aryl = 4‐nitrophenyl, m = 1 (H2A1); 4‐chlorophenyl, m = 2 (H2A2); phenyl, m = 2 (H2A3); 4‐hydroxyphenyl, m = 2 (H2A4); 4‐methoxyphenyl, m = 2 (H2A5); 4‐hydroxy‐3‐methoxyphenyl, m = 1.5 (H2A6); 2‐nitrophenyl, m = 1.5 (H2A7); 3‐nitrophenyl, m = 0.5 (H2A8); p‐tolyl, m = 1 (H2A9) and HL = 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐(piperazin‐1‐yl)‐1,4‐dihydroquinoline‐3‐carboxylic acid] were investigated. They were characterized by elemental analysis (FT‐IR, 1H‐ & 13C‐NMR, and electronic) spectra, magnetic measurements and thermal studies. The FAB‐mass spectrum of [Fe(A3)(L)(H2O)2]?2H2O was determined. Magnetic moment and reflectance spectral studies revealed that an octahedral geometry could be assigned to all the prepared heterochelates. Ligands (H2An) and their heterochelates were screened for their in‐vitro antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Serratia marcescens bacterial strains. The kinetic parameters such as order of reaction (n), the energy of activation (Ea), the pre‐exponential factor (A), the activation entropy (ΔS#), the activation enthalpy (ΔH#) and the free energy of activation (ΔG#) are reported. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

13.
The equilibrium association free enthalpies ΔGa for typical supramolecular complexes in solution are calculated by ab initio quantum chemical methods. Ten neutral and three positively charged complexes with experimental ΔGa values in the range 0 to ?21 kcal mol?1 (on average ?6 kcal mol?1) are investigated. The theoretical approach employs a (nondynamic) single‐structure model, but computes the various energy terms accurately without any special empirical adjustments. Dispersion corrected density functional theory (DFT‐D3) with extended basis sets (triple‐ζ and quadruple‐ζ quality) is used to determine structures and gas‐phase interaction energies (ΔE), the COSMO‐RS continuum solvation model (based on DFT data) provides solvation free enthalpies and the remaining ro‐vibrational enthalpic/entropic contributions are obtained from harmonic frequency calculations. Low‐lying vibrational modes are treated by a free‐rotor approximation. The accurate account of London dispersion interactions is mandatory with contributions in the range ?5 to ?60 kcal mol?1 (up to 200 % of ΔE). Inclusion of three‐body dispersion effects improves the results considerably. A semilocal (TPSS) and a hybrid density functional (PW6B95) have been tested. Although the ΔGa values result as a sum of individually large terms with opposite sign (ΔE vs. solvation and entropy change), the approach provides unprecedented accuracy for ΔGa values with errors of only 2 kcal mol?1 on average. Relative affinities for different guests inside the same host are always obtained correctly. The procedure is suggested as a predictive tool in supramolecular chemistry and can be applied routinely to semirigid systems with 300–400 atoms. The various contributions to binding and enthalpy–entropy compensations are discussed.  相似文献   

14.
A 32‐membered library of poly(2‐oxazoline)‐based hydrogels of the composition p EtOx m‐p PhOx n‐p PBO q (m/n = 150/0, 100/50, 50/100, and 0/150; q = 1.5–30) was prepared from 2‐ethyl‐ ( EtOx ), 2‐phenyl‐2‐oxazoline ( PhOx ), and phenylene‐1,3‐bis‐(2‐oxazoline) ( PBO ). The polymerizations were performed from ground monomer mixtures at 140 °C in a single‐mode microwave reactor in reaction times as short as 1 h. Purified hydrogels, containing no residual monomers, were obtained in yields of 95% or higher. Acid‐mediated hydrolysis rates as well as swelling degrees of the hydrogels were adjustable over a broad range; swelling degrees in water/ethanol/dichloromethane ranged from 0 to 13.8/11.7/20.0. The hydrogels could incorporate organic molecules according to in situ or post‐synthetic routines. Post‐synthetic routines enabled for the preparation of hydrogels from which the incorporated compounds were only released through diffusion processes if the solvent was changed or through hydrogel degradation if the pH was lowered.  相似文献   

15.
Atomistic dynamics of protonated polyglycine, glyn‐H+ (n = 3, 5, and 7), colliding with a fluorinated octanethiol self‐assembled monolayer (F‐SAM) surface has been studied by trajectory calculations. The effects of peptide size on the collision processes and energy transfer efficiencies are emphasized and discussed in detail. The simulations show that the fraction of trapping, which is related to the soft‐landing process, dramatically drops with the increase in collision energy, but gently increases with the peptide size. The average energy transfer to the peptide ion's internal degrees of freedom, ΔEint, is compared with previous experiments. The limiting probability Po of energy transfer to the surface is given by fitting a function of Poexp(–b/Ei). Our results suggest that the efficiencies of energy transfer are less dependent on the masses, even the categories of the peptide ions, and are determined by the character of the surfaces.  相似文献   

16.
A series of poly(cyclohexylethylene‐b‐ethylene‐co‐ethylethylene) (C‐E/EE) diblock copolymers containing approximately 50% by volume glassy C blocks and varying fraction (x) of EE repeat units, 0.07 ≤ x ≤ 0.90, was synthesized by anionic polymerization and catalytic hydrogenation. The effects of ethyl branch content on the melt state segment–segment (χ) interaction parameter and soft (E/EE) block crystallinity were studied. The percent crystallinity ranged from approximately 30% at x = 0.07 to 0% at about x ≥ 0.30, while the melting temperature changed from 101 °C at x = 0.07 to 44 °C at x = 0.28. Dynamic mechanical spectroscopy was employed to determine the order–disorder transition (ODT) temperatures, from which χ was calculated assuming the mean‐field prediction (χNn)ODT = 10.5. Previously published results for the temperature dependent binary interaction parameters for C‐E (x = 0.07), C‐EE (x = 0.90), and E‐EE (x = 0.07 and x = 0.90) fail to account for the quantitative x dependence of χ, based on a simple binary interaction model. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 566–574, 2010  相似文献   

17.
Using an oxenoid model, we investigated dependences of carcinogenic potency of the benzenes C6H5‐X on a nature of substituents X. According to the model, a P450 enzyme breaks a dioxygen molecule and generates the oxens, which readily react with substrates. We suggest that a stability of the intermediate OC6H6‐X with tetrahedrally coordinated C atom relative to the molecule C6H5‐X determines a rate of substrate biotransformation. Using MO LCAO MNDO approach, we calculated the total energies of molecules C6H6‐X and arene oxides OC6H6‐X. A difference ΔEmin of these values determines activation energy of oxidation reaction. The compounds with the low ΔEmin values are noncarcinogenic. Benzene derivatives with high ΔEmin values belong to carcinogenic compounds series. The carcinogenicity of amino‐ and nitro‐substituted benzenes is also determined by N‐oxidation of amino and reduction of the nitro group. As the phenylhydroxylamines XC6H4NHOH and nitrenium ions XC6OH4NH+ are the common metabolites of the nitro‐ and amino‐substituted benzenes and nitrenium ions XC6H4NH+ are the ultimate carcinogens, we use the differences ΔEN = E(XC6H4NH+) ? E(XC6H4NHOH) as the second parameter characterizing the carcinogenic activity of amino‐ and nitro‐substituted benzenes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010  相似文献   

18.
19.
We prepared and isolated a phenalenyl‐based neutral hydrocarbon ( 1 b ) with a biradical index of 14 %, as well as its charge‐transfer (CT) complex 1 b –F4‐TCNQ. The crystal structure and the small HOMO–LUMO gap assessed by electrochemical and optical methods support the singlet‐biradical contribution to the ground state of the neutral 1 b . This biradical character suggests that 1 b has the electronic structure of phenalenyl radicals coupled weakly through an acetylene linker, that is, some independence of the two phenalenyl moieties. The monocationic species 1 b. + was obtained by reaction with the organic electron acceptor F4‐TCNQ. The cationic species has a small disproportionation energy ΔE for the reaction 2× 1 b. +? 1 b + 1 b 2+, which presumably originates from the independence of the phenalenyl moieties. The small ΔE led to a small on‐site Coulombic repulsion Ueff=0.61 eV in the CT complex. Moreover, a very effective orbital overlap of the phenalenyl rings between molecules afforded a relatively large transfer integral t=0.09 eV. The small Ueff/4t ratio (=1.7) resulted in a metallic‐like conductive behavior at around room temperature. Below 280 K, the CT complex showed a transition into a semiconductive state as a result of bond formation between phenalenyl and F4‐TCNQ carbon atoms.  相似文献   

20.
A training set of eleven X‐ray structures determined for biomimetic complexes between cucurbit[n]uril (CB[7 or 8]) hosts and adamantane‐/diamantane ammonium/aminium guests were studied with DFT‐D3 quantum mechanical computational methods to afford ΔGcalcd binding energies. A novel feature of this work is that the fidelity of the BLYP‐D3/def2‐TZVPP choice of DFT functional was proven by comparison with more accurate methods. For the first time, the CB[n] ? guest complex binding energy subcomponents [for example, ΔEdispersion, ΔEelectrostatic, ΔGsolvation, binding entropy (?TΔS), and induced fit Edeformation(host), Edeformation(guest)] were calculated. Only a few weeks of computation time per complex were required by using this protocol. The deformation (stiffness) and solvation properties (with emphasis on cavity desolvation) of cucurbit[n]uril (n=5, 6, 7, 8) isolated host molecules were also explored by means of the DFT‐D3 method. A high ρ2=0.84 correlation coefficient between ΔGexptl and ΔGcalcd was achieved without any scaling of the calculated terms (at 298 K). This linear dependence was utilized for ΔGcalcd predictions of new complexes. The nature of binding, including the role of high energy water molecules, was also studied. The utility of introduction of tethered [‐(CH2)nNH3]+ amino loops attached to N,N‐dimethyl‐adamantane‐1‐amine and N,N,N′,N′‐tetramethyl diamantane‐4,9‐diamine skeletons (both from an experimental and a theoretical perspective) is presented here as a promising tool for the achievement of new ultra‐high binding guests to CB[7] hosts. Predictions of not yet measured equilibrium constants are presented herein.  相似文献   

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