First heterobimetallic AgI–CoIII coordination compound with both bridging and terminal –NO2 coordination modes: synthesis,characterization, structural and computational studies of (PPh3)2AgI–(μ‐κ2O,O′:κN‐NO2)–CoIII(DMGH)2(κN‐NO2)

An unusual heterobimetallic bis(triphenylphosphane)(NO₂)Ag^I–Co^III(dimethylglyoximate)(NO₂) coordination compound with both bridging and terminal –NO₂ (nitro) coordination modes has been isolated and characterized from the reaction of [CoCl(DMGH)₂(PPh₃)] (DMGH₂ is dimethylglyoxime or N,N′‐dihydroxybutane‐2,3‐diimine) with excess AgNO₂. In the title compound, namely bis(dimethylglyoximato‐1κ²O,O′)(μ‐nitro‐1κN:2κ²O,O′)(nitro‐1κN)bis(triphenylphosphane‐2κP)cobalt(III)silver(I), [AgCo(C₄H₇N₂O₂)₂(NO₂)₂(C₁₈H₁₅P)₂], one of the ambidentate –NO₂ ligands, in a bridging mode, chelates the Ag^I atom in an isobidentate κ²O,O′‐manner and its N atom is coordinated to the Co^III atom. The other –NO₂ ligand is terminally κN‐coordinated to the Co^III atom. The structure has been fully characterized by X‐ray crystallography and spectroscopic methods. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) have been used to study the ground‐state electronic structure and elucidate the origin of the electronic transitions, respectively.     

Theoretic design of 1,2,3,4-tetrazine-1,3-dioxide-based high-energy density compounds with oxygen balance close to zero

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and thermal stability for a series of 1,2,3,4-tetrazine-1,3-dioxide derivatives with different substituents and bridge groups. It is found that the groups –NO₂, –C(NO₂)₃, and –N=N– play a very important role in increasing the HOFs of the derivatives. The effects of the substituents on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels and HOMO–LUMO gaps are coupled to those of different substituents and bridges. The calculated detonation velocities and pressures indicate that the group –NO₂, –NF₂, –ONO₂, –C(NO₂)₃, or –NH– is an effective structural unit for enhancing the detonation performance for the derivatives. An analysis of the bond dissociation energies for several relatively weak bonds indicates that incorporating the groups –NO₂, –NF₂, –ONO₂, –C(NO₂)₃, and –N=N– into parent ring decreases their thermal stability. Considering the detonation performance and thermal stability, 18 compounds may be considered as the target compounds holding the greatest potential for synthesis and use as high-energy density compounds. Among them, the oxygen balances of four compounds are equal to zero. These results provide basic information for the molecular design of the novel high-energy compounds.     

Comparative theoretical studies of substituted bridged bipyridines and their N-oxides

In this work, the experimental synthesized bipyridines azo-bis(2-pyridine),4,4′-dimethyl-3,3′-dinitro-2,2′-azobipyridine, and N,N′-bis(3-nitro-2-pyridinyl)-methane-diamine and a set of designed bipyridines that have similar frameworks but different linkages and substituents were studied theoretically at the B3LYP/6-31G* level of density functional theory. The gas-phase heats of formation were predicted based on the isodesmic reactions, and the condensed-phase heats of formation and heats of sublimation were estimated in the framework of the Politzer approach. The crystal densities have been computed from molecular packing and results show that incorporation of –N=N–, –N=N(O)–, –CH=N–, and –NH–NH– into bipyridines is more favorable than –CH=CH– and –NH–CH₂–NH– for increasing the density. The predicted detonation velocities (D) and detonation pressures (P) indicate that –NH₂, –NO₂, and –NF₂ can enhance the detonation performance, and –NO₂ and –NF₂ are more favorable. Introducing –N=N–, –N=N(O)–, and –NH–NH– bridge groups into bipyridines is also favorable for improving their detonation performance. The oxidation of pyridine N always but that of –N=N– bridge does not always improve the detonation properties. E4–O, the derivative with –N=N– bridge and two –NF₂ substituent groups, has the largest D (9.90 km/s) and P (47.47 GPa). An analysis of the bond dissociation energies shows that all derivatives have good thermal stability.     

Investigation of the Effect of Various Substituents on the Density of Tetrazolium Nitrate Salts as Green Energetic Materials

The substitution effect of various functional groups such as –NO₂, –CN, –N₃, –NF₂, and –NH₂ on the density of tetrazolium nitrate salts is investigated through multiple linear regression method. The methodology of this work introduces a new model, which related density of tetrazolium nitrate salts to the number of fluorine and nitrogen atoms, the presence of NF₂ groups, NO₂ groups, as well as CH₃ groups in the structural formula. The new reliable correlation shows that the NF₂ and NO₂ group can cause increasing the density of tetrazolium nitrate salts, especially NO₂, whereas the CH₃ group can decrease their density. The new proposed relationship has good reliability and predictability, so it can be used to design new rich nitrogen compounds based on tetrazolium nitrate salts as green energetic materials. These results are also tested for N,N′‐azo‐1,2,4‐triazolium nitrate salts, which is caused to derive another correlation. This correlation shows that the presence of NF₂ functional groups increases the density of N,N′‐azo‐1,2,4‐triazolium nitrate salts as well as the value of n_O/n_C.     

Excited electronic and ionized states of the nitramide molecule, H2NNO2, studied by the symmetry-adapted-cluster configuration interaction method

Symmetry-adapted-cluster configuration interaction (SAC-CI) wave functions were employed to compute 16 singlet and 13 triplet vertical transitions, and 14 ionized states including relative intensities of the nitramide molecule, H₂NNO₂. This molecule is the simplest neutral closed-shell molecule which has an N–NO₂ bond and is a member of the nitramine family, R,R′N(NO₂), an important class of energetic materials with practical applications. The present nitramide results showed strong similarities with the ones of the N, N-dimethylnitramine molecule, which has also an N–NO₂ bond and was previously studied using the SAC-CI method. Experimental ultraviolet and photoelectron band spectra of the nitramide molecule could be successfully assigned. All the singlet transitions have valence character. The computed singlet and triplet transitions, excepting a singlet one, result from excitation originating in the four highest occupied molecular orbitals, which have close energies. Most of the singlet and triplet transitions involved mixing of singly excited configurations. The strongest computed transition, at 6.8 eV, is a mixture of two nπ_NO2 → π^* configurations corresponding to excitations from the highest occupied molecular orbital (HOMO) to the first two virtual orbitals and has an optical oscillator strength value of 0.2665. The computed ionized states described the whole measured spectrum, have excellent agreement when compared with the measured ionization potentials and revealed an inversion of the ordering of the first states not expected according to Koopmanns’ theorem, thereby showing the limitations of the latter.     

Synthesis and Structure of Cyclic Selenium Oxide SeVISe2IVO7

Nitromethane is the only presently known organic solvent for highly reactive selenium trioxide (SeO₃)₄. The stability of the solutions is limited and the beginning of the reaction between both components depends significantly on concentration and temperature. The nitromethane solvate of cyclic triselenium heptoxide Se₃O₇ · CH₃NO₂ is the major solid product at the temperature 20–30°C and concentration range 3–20% SeO₃. Crystal and molecular structure of this compound was determined by X-ray structure analysis and vibrational spectroscopy. The solvating molecule CH₃NO₂ is removable from Se₃O₇ · CH₃NO₂ in vacuo. If reaction temperature does not exceed 10°C, selenium pentoxide (Se₂O₅)_n is formed instead of Se₃O₇ · CH₃NO₂. Dinitrosyl triselenate (NO)₂Se₃O₁₀, nitrosyl hydrogendiselenate NOHSe₂O₇, nitrosyl hydrogenselenate NOHSeO₄, nitrosyl hydrogenselenatoselenite NOHSe₂O₆ and selenium dioxide (SeO₂)_n were further identified in the solid reaction products. The selenic and/or oligoselenic acids remains in the nitromethane solution. CO₂ and N₂O₃ were found as gaseous products.     

Linear-Reactor-IR.-Matrix and Microwave Spectroscopy of the System O3/NO2/(Z)-2-Butene

Investigation of the formation of complex reaction products in the gas-phase system O₃/NO₂/(Z)-2-butene by combination of linear reactors with IR. matrix and microwave Stark Spectroscopy is reported. Besides the polyatomic products observed earlier in the gas-phase ozonolysis of (Z)-2-butene, the following products were identified; N₂O₅, HNO₃, HNO₄, CH₃NO₂, CH₃ONO, CH₃COONO₂ and CH₃COO₂NO₂ (peroxyacetyl nitrate, PAN). Matrix IR. spectra of N₂O₅, HNO₃. CH₃COONO, CH₃COONO₂ required for reference purposes are presented. It is shown that PAN-formation occurs already in the absence of light. A reaction scheme is proposed for explanation of the observed complex NO_x-containing products, which assumes methyldioxirane as a central intermediate. Particular reaction steps of the scheme will be discussed, including thermochemical estimates of reaction enthalpies.     

Electronically excited oxygen atoms,O(21D2). A time-resolved study of the collisional quenching by the gases H2, D2, CH4, NO,NO2, N2O,and C3O2 using atomic absorption spectroscopy in the vacuum ultraviolet

Time-resolved atomic absorption spectroscopy in the vacuum ultraviolet has been employed to monitor electronically excited oxygen atoms, O(2¹D₂), following their genera-tion by the flash photolysis of ozone in the Hartley band region. We report the first values for the absolute second-order rate constants describing the removal of the excited atom on collision with the molecules H₂, D₂, CH₄, NO, NO₂, N₂O, and C₃O₂. Where possible, these data are considered within the context of restrictions arising from spin and orbital symmetry and are further discussed in tems of previously reported relative rate data derived from indirect measurements. Consideration is given to the importance of these rate con-stants in discussing processes taking place in the earth's atmosphere and in systems giving rise to chemical laser action.     

A theoretical study on surface modification of a nanosized BC3 tube using C2H4 and its derivatives

Chemical functionalization of a BC₃ nanotube (BC₃NT) with C₂X₄ (X = –H, –F, –CH₂F, –CN, –NH₂, –NO₂, –CH₃, and –OCH₃) was investigated by density functional theory calculations. It was found that C₂H₄ prefers to be added to a B–C bond of the tube wall. The interaction energies are calculated to be ranging from ?0.03 to ?40.32 kcal/mol, and their relative magnitude order is found to be as follows: C₂F₄ > C₂(NH₂)₄ > C₂H₄ > C₂(NO₂)₄ > C₂(OCH₃)₄ > C₂(CN₄)₂ > C₂(CH₃)₄ > C₂(CH₂F)₄. For chemically modified BC₃NTs with various functional groups, the functionalization energy can be correlated with the trend of relative electron-withdrawing or electron-donating capability of the adsorbates. The calculated density of states shows that the functionalization of BC₃NT with these functional groups (except C₂(NO₂)₄) can be generally classified as a certain type of “electronically harmless modification”. We believe that the preservation of electronic properties of BC₃NTs coupled with the enhancement of solubility may render the chemical modification to be an effective way for the purification of BC₃NTs. The insight provided by this theoretical study may also assist future development of BC₃NTs with targeted chemoselectivity through chemical functionalization.     

Theoretical studies on the structures, heats of formation, energetic properties and pyrolysis mechanisms of nitrogen-rich difurazano[3,4-b:3′,4′-e]piperazine derivatives and their analogues

The molecular structure, heats of formation, energetic properties, strain energy and thermal stability for a series of substituted difurazano[3,4-b:3′,4′-e]piperazines and their analogues were studied using density functional theory. The results show that it is a useful way to increase the heat of formation values of energetic compounds by incorporating a five- or six-membered aromatic heterocycle to construct a fused ring system. The calculated detonation properties reveal that introducing one heterocycle to construct a fused ring structure greatly enhances their detonation properties. The substitution of the –NF₂, –NO₂ or –NHNO₂ group is very useful for enhancing the detonation performance for the substituted derivatives. According to molecular structure and natural bond orbital analysis, the introduction of the –NO₂, –NF₂ or –NHNO₂ group decreases the stability of the substituted derivative. There is a weak N–NO₂ bond conjugation in the NO₂-substituted derivatives. An analysis of the bond dissociation energies for several relatively weak bonds suggests that all the unsubstituted derivatives have good thermal stability, but the substitution of –NO₂ or –NF₂ remarkably decreases their stability. Considering the detonation performance and thermal stability, eight compounds may be considered as the potential candidates of high-energy density materials with less sensitivity.     

Synthesis and characterization of O,O′-dialkyl and alkylene dithiophosphates of thorium(IV) and their adducts with nitrogen and phosphorus donors

Thorium(IV) tetrakis(dithiophosphates), [Th{S₂P(OR)₂}₄] (where R?=?–CH₂CH₂CH₃ or –C₆H₅) and [Th{S₂PO₂G}₄] [where G?=?–C(CH₃)₂CH₂CH(CH₃)–, –CH₂C(CH₃)₂CH₂–, –C(CH₃)₂C(CH₃)₂– and –CH₂CH₂CH(CH₃)–] were prepared in methanolic solution of Th(NO₃)₄???6H₂O and ammonium dithiophosphates. Adducts of the type [Th{S₂P(OR)₂}₄???nL] and [Th{S₂PO₂G}₄???nL] [where n?=?1, L?=?N₂C₁₀H₈ or N₂C₁₂H₈ and n?=?2, L?=?P(C₆H₅)₃] were prepared by the reaction of thorium(IV) tetrakis(dithiophosphates) and nitrogen or phosphorus donors in benzene. These newly synthesised derivatives have been characterized by elemental analyses, molecular weights, IR, ¹H and ³¹P NMR spectral measurements. Coordination numbers of eight and ten are suggested for thorium(IV) in these derivatives.     

Anion-controlled geometrically different Cu(II) ion-based coordination polymers and green synthetic route for copper nanoparticles: a combined experimental and computational insight

Abstract

The Cu(II) ion-based polymeric complexes [Cu(2,2′-bpy).(N₃)₂]_n (I), [Cu₂(2,2′-bpy)₂.(N₃)₄]_n (II), and monomeric complex [Cu(2,2′-bpy).(NO₃)₂].5H₂O (III) have been synthesized with rigid (–N₃) and aromatic (2,2′-bpy = 2,2′-bipyridyl) ligand. The rigid azide group is responsible for the formation of 1-D extended structures in complexes I and II where as in the case of complex III, a monomeric complex is formed due to lack of a bridging group like –N₃, resulting in limitation in dimensionality. The thermal stability of the 1-D complexes is comparatively higher than monomeric complex III. Hirshfeld surface analysis has also been applied to investigate other weak interactions and compared with the results from single-crystal X-ray data. Due to the presence of paramagnetic metal centers and long metal···metal distances in complexes I and II and presence of lattice water molecules in complex III, decrease in luminescence intensities have been observed. To attain further insights into the aforementioned interesting species, some chemical concepts such as highest occupied molecular orbital–lowest unoccupied molecular orbital gap, electronic chemical potential, chemical hardness, and electrophilicity index, identified as a derivative of electronic energy, have also been emphasized employing the quantum chemical calculations in the framework of the density functional theory method using the M06-2X/ 6-31G** level of study. Further, these complexes have been used to synthesize copper nanoparticles by applying a green synthetic route.     

2D Compound Constructed by Cu3 Units with Mixed Azido and Tetrazole Double Bridges: Synthesis,Structure, and Theoretical Study on Magnetic Properties

The two‐dimensional (2D) layer Cu^II compound [Cu₃(L)₂(N₃)₄] ( 1 ) [L = 2‐amino‐3‐(5‐tetrazole)‐methyate‐N‐pyridine] was synthesized by in‐situ hydrothermal reaction of CuCl₂ · 2H₂O, NaN₃, and 3‐(5‐tetrazole)‐methyate‐N‐pyridine. The central Cu1 and Cu2 atoms are located in five‐coordinate and six‐coordinate arrangements, respectively. Three Cu^II ions are linked by mixed double EO (end‐on)‐azido‐tetrazole bridges to give trinuclear Cu^II clusters, which are further extended by EE (end‐to‐end) azido bridges to form 2D metal‐organic layers. The magnetic exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –849 cm^–1) revealed that the double EO‐azido‐tetrazole bridges transmit antiferromagnetic coupling between Cu^II ions.     

Temperature effects on positronium formation and inhibition: a contribution to the elucidation of early spur processes. I. Glycerol/water mixtures

In order to elucidate the mechanism of positronium (Ps) formation in liquids, the effect of temperature, T, on the inhibiting properties of various solutes has been investigated in glycerol/water mixtures. Whereas the inhibition constants of Cl^? and I^? are found to increase markedly with T, that of CH₃NO₂ is T insensitive and that of NO₃^? diminishes with T. These findings are consistent with our previous model, according to which Ps would be formed via two pathways, either through the quasi-free entities or by the reaction of localized, not yet fully solvated, electrons and positrons. The increase with T of the Ps yield is found to be due to the fraction arising from the latter reaction. The results confirm Cl^? and I^? react with e_loc⁺, while CH₃NO₂ and NO₃^? scavenge quasi-free electrons. Regarding the behaviour of the inhibition constants of these latter solutes, a provisional explanation is given: CH₃NO₂ would scavenge epithermal electrons while NO₃^? would react with electrons at a lower energy state, in competition with the localization process. Hot Ps atoms are not likely to be involved.     

Double End‐On Azido Copper(II) Dinuclear Complex with Oxazoline Ligand: Synthesis,Structure, Magnetic Properties and Theoretical Study

A double azido‐bridged Cu^II dinuclear complex with the chelating chiral ligand, [Cu₂(L)₂(N₃)₄] ( 1 ) [L = (+)‐2, 2′‐isopropylidene‐bis((4R)‐4‐benzyl‐2‐oxazoline)] was synthesized and characterized by single‐crystal X‐ray diffraction, IR spectroscopy, magnetic measurements, and theoretical studies. The asymmetric double end‐on azido bridges in complex 1 lead to a weak antiferromagnetic behavior with J = –7.4 cm^–1. The exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –8.0 cm^–1) is in good agreement with the experimental value.     

Synthesis and Structural Characterization of the First Europium(III) Pyridylphosphine Complex, [Eu(N,N’,N”-2-Py3P)(NO3)3]

The first europium(iii) pyridylphosphine complex, [Eu(N,N’,N”-2-Py₃P)(NO₃)₃] was prepared by the reaction between Eu(NO₃)₃.6H₂O and tris(2-pyridyl)phosphine; its structure was characterized by single-crystal X-ray diffraction.     

Kinetics of gas‐phase reactions of CH3OCH2CF3, CH3OCH3, CH3OCH2CH3, CH3CH2OCH2CH3, and CHF2CF2OCH2CF3 with NO3 radicals at 298 K

Rate constants for the gas‐phase reactions of CH₃OCH₂CF₃ (k₁), CH₃OCH₃ (k₂), CH₃OCH₂CH₃ (k₃), and CH₃CH₂OCH₂CH₃ (k₄) with NO₃ radicals were determined by means of a relative rate method at 298 K. NO₃ radicals were prepared by thermal decomposition of N₂O₅ in a 700–750 Torr N₂O₅/NO₂/NO₃/air gas mixture in a 1‐m³ temperature‐controlled chamber. The measured rate constants at 298 K were k₁ = (5.3 ± 0.9) × 10^?18, k₂ = (1.07 ± 0.10) × 10^?16, k₃ = (7.81 ± 0.36) × 10^?16, and k₄ = (2.80 ± 0.10) × 10^?15 cm³ molecule^?1 s^?1. Potential energy surfaces for the NO₃ radical reactions were computationally explored, and the rate constants of k₁–k₅ were calculated according to the transition state theory. The calculated values of rate constants k₁–k₄ were in reasonable agreement with the experimentally determined values. The calculated value of k₅ was compared with the estimate (k₅ < 5.3 × 10^?21 cm³ molecule^?1 s^?1) derived from the correlation between the rate constants for reactions with NO₃ radicals (k₁–k₄) and the corresponding rate constants for reactions with OH radicals. We estimated the tropospheric lifetimes of CH₃OCH₂CF₃ and CHF₂CF₂OCH₂CF₃ to be 240 and >2.4 × 10⁵ years, respectively, with respect to reaction with NO₃ radicals. The tropospheric lifetimes of these compounds are much shorter with respect to the OH reaction. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 490–497, 2009     

Sulphur substituted organotin compounds : IX. Formation of [(3-chloro-4-o-nitrophenylthio)butyl]-triphenyltin,Ph3SnCH2CH2CHClCH2SC6H4NO2-o,from reaction of 4-butenyltriphenyltin and o-nitrobenzenesulphenyl chloride

Reaction of the sulphenyl chloride, o-NO₂C₆H₄SCl, with Ph₃SnCH₂CH₂CHCH₂ occurs to give the adduct, Ph₃SnCH₂CH₂CHClCH₂SC₆H₄NO₂-o. In contrast, no adduct is formed with the more reactive, p-MeC₆H₄SCl. Instead, and as reported previously with Bu₃SnCH₂CH₂CHCH₂, the cyclopropylmethyl aryl sulphide is obtained. The adduct is thermally stable, and reacts with I₂ and HgCl₂ to give phenyld-tin cleaved products, Ph₂SnXCH₂CH₂CHClCH₂SC₆H₄NO₂-o (X = I or Cl).     

Theoretical investigation of a high density cage compound 1,3,5,7,9,11-hexanitrotetradecahydro-1H-1,3,4,5,7,7b,9,11,12a,12b1,12b2,13-dodecaaza-4,8,12-(epimethanetriyl)cyclohepta[l]cyclopenta[def] phenanthrene

The B3LYP/6-31G** method was used to investigate IR and Raman spectra, heat of formation, and thermodynamic properties of a new designed polynitro cage compound 1,3,5,7,9,11-hexanitrotetradecahydro-1H-1,3,4,5,7,7b,9,11,12a,12b¹,12b²,13-dodecaaza-4,8,12-(epimethanetriyl)cyclohepta[l]cyclopenta[def]phenanthrene. The detonation and pressure were evaluated using the Kamlet–Jacobs equations based on the theoretical density and HOFs. The bond dissociation energies and bond orders for the weakest bonds were analyzed to investigate the thermal stability of the title compound. The results show that N₈–NO₂ bond is predicted to be the trigger bond during pyrolysis. There exists an essentially linear relationship between the WBIs of N–NO₂ bonds and the charges – $ Q_{{{\text{NO}}_{ 2} }} $ on the nitro groups. The crystal structure obtained by molecular mechanics belongs to the P2₁ space group, with lattice parameters Z = 2, a = 11.4658 Å, b = 15.2442 Å, c = 10.2451 Å, ρ = 2.07 g cm^?3. The designed compound has high thermal stability and good detonation properties and is a promising high-energy density compound.