Ab initio study of energetic solids: cupric azide, mercuric azide, and lead azide

We presented a detailed study on the electronic structure and optical properties of cupric azide (Cu(N(3))(2)), mercuric azide (alpha-Hg(N(3))(2)), and lead azide (alpha-Pb(N(3))(2)) by using density functional theory within the generalized gradient approximation. Relaxed crystal structures compare well with experimental data. An analysis of electronic structure, charge transfer, and bond order shows that Cu(N(3))(2) and alpha-Hg(N(3))(2) are covalent-type solids, whereas alpha-Pb(N(3))(2) is an ionic-type solid but has weak covalent character. The valence bands of Cu(N(3))(2) and alpha-Hg(N(3))(2) arise from the contributions of the metal-d and N-p states, whereas that of alpha-Pb(N(3))(2) are strongly dominated by N-p states and not from Pb-d states. The general shapes of the real and imaginary parts of the dielectric function, adsorption coefficient, and photoconductivity spectra for the three azides are similar. Our calculated optical properties are found to be in agreement with available experimental data. The absorption spectra show a number of absorption peaks in the fundamental absorption region. All the photoconductivity spectra display a broad photocurrent response in the fundamental absorption region. The density of states of the three azides reveal the effects of the metal states on the valence electron of the azide group and so are correlated with their impact sensitivity.     

High energy binders: glycidyl azide and allyl azide polymer

Hydroxy-terminated azido polymers such as poly(glycidyl azide), poly bis(azidomethyl oxetane) and poly(azidomethyl methyloxetane) have been investigated in the past in propellent formulations and as fuels in rocket technology. The high energy released upon the decomposition of the azido group is responsible for their specialized application as high-energy binders. The present paper describes the synthesis and characterization of new low molecular mass azido polymer i.e. poly(allyl azide). The curing reaction was carried out by using 1,3-cyclic dipolar addition reaction. The dipolarophiles, such as dimethylene glycol dimethacrylate (EGDMA) and addition polyimides (bismaleimides, bisnadimides and bisitaconimides) were used for curing of azido polymers. The curing reaction was monitored by FT-IR and differential scanning calorimetry. Curing was carried out at 40°C for 16 h (EGDMA) or 2 days (bismaleimide) and then at 60°C by using different phr of dipolarophiles. The heat of exothermic transition, due to decomposition of azide groups and thermal polymerization of addition polyimides, was very high and an improvement in thermal stability of cured resins was observed.     

Asymmetric syntheses with BINOL-based imidoyl azide

Thermal decomposition of 2,4,6-trimethylphenyl and (+)-2′-methoxy-1,1′-binaphthalen-2-yl (4-methylphenylsulfonyl)azidimidocarbonates in the presence of norbornene, methyl acrylate, and camphene was studied. (+)-2′-Methoxy-1,1′-binaphthalen-2-yl (4-methylphenylsulfonyl)azidimidocarbonate reacted with norbornene to give (+)-exo-2′-methoxy-1,1′-binaphthalen-2-yl N-(4-methylphenylsulfonyl)-3-azatricyclo-[3.2.1.0^2,4]octane-3-carboximidoate, while in the reaction with methyl acrylate a mixture of stereoisomeric methyl 1-[(2′-methoxy-1,1′-binaphthalen-2-yloxy)(4-methylphenylsulfonylimino)methyl]aziridine-2-carboxylates was obtained. The reaction of 2,4,6-trimethylphenyl (4-methylphenylsulfonyl)azidimidocarbonate with (−)-camphene involved insertion of intermediate nitrene into the exocyclic double bond with formation of 2,4,6-trimethylphenyl N-(3,3-dimethylbicyclo[2.2.1]heptan-2-ylidenemethyl)-N′-(4-methylphenylsulfonyl)-imidocarbamate as a 3: 1 mixture of E,E and E,Z diastereoisomers in good yield. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 10, pp. 1495–1500. The text was submitted by the authors in English.     

Nitroguanyl azide

Crystals of the title compound, nitro­carbam­imidoyl azide, CH₂N₆O₂, consist of two symmetry‐independent mol­ecules and the structure is stabilized by intra‐ and intermolecular hydrogen bonds. The mol­ecule possesses a nitr­imine structure.     

Photolysis of thallium azide

Preliminary treatment of TlN₃(A) with light (λ = 365 nm, I > 1 × 10¹⁴ quantum cm⁻² s⁻¹) in a vacuum (1 × 10⁻⁵ Pa) at 293 K led to the formation of a new long-wave region of spectral sensitivity. The products of photolysis of TlN₃(A) thallium and nitrogen formed in the stoichiometric ratio on the sample surface. The topography and kinetics of thallium accumulation were determined, and the effective rate constants for photolysis evaluated. Measurements of the contact voltage, current-voltage characteristics, and photocurrent showed that the photolysis of thallium azide resulted in the formation of TlN₃(A)-Tl (photolysis product) microheterogeneous systems. A model of photolysis of TlN₃(A) was suggested. According to this model, photolysis included the generation, recombination, and redistribution of nonequilibrium charge carriers in the contact field and the formation of the end products of photolysis. The limiting stage of photolysis of TlN₃(A) was the diffusion of interstitial thallium cations toward the neutral (T _n Tl _m )⁰ center. Original Russian Text ? E.P. Surovoi, L.I. Shurygina, L.N. Bugerko, N.V. Borisova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 784–790.     

New tests for the detection of azide

Two new, simple, reliable, and specific colour tests are described for the detection of azide. In one, the azide is heated with allyl isothiocyanate and water to form 1-allyl-2-tetrazoline-5-thione in solution; the latter gives a yellow precipitate on treatment with bismuth nitrate solution. Pyridine enhances the intensity of the colour. The allyl isothiocyanate can be produced in situ by treating allylamine with carbon disulphide, diethylamine and hydrogen peroxide. In the other test the azide is heated with carbon disulphide, water and acetone, resulting in the formation of 1,2,3,4-thiatriazoline-5-thione which gives a yellow precipitate with Cu(II) or Bi(III). Pyridine again enhances the colour. The method is applicable to 5-10 mg of soluble azides, but insoluble azides cannot be tested. CN(-), SCN(-), and other common anions do not interfere. Only S(-2) interferes by masking the colour (black CuS or Bi(2)S(3) is precipitated). NO(2)(-) in larger amounts interferes in the second test.     

Cobalt-catalyzed asymmetric olefin aziridination with diphenylphosphoryl azide

The cobalt(II) complexes of D2-symmetric chiral porphyrins, such as 3,5-Di(t)Bu-ChenPhyrin P5, can catalyze asymmetric olefin aziridination with diphenylphosphoryl azide (DPPA) as a nitrene source. Acceptable asymmetric inductions were observed for the [Co(P5)]-based catalytic system, forming the desired N-phosphorus-substituted aziridines in moderate to high yields and good enantioselectivities.     

Preparation of benzyl azide complexes of iridium(III)

Hydride complexes IrHCl(2)(PiPr(3))P(2) (1) and IrHCl(2)P(3) (2) [P = P(OEt)(3) and PPh(OEt)(2)] were prepared by allowing IrHCl(2)(PiPr(3))(2) to react with phosphite in refluxing benzene or toluene. Treatment of IrHCl(2)P(3), first with HBF(4).Et(2)O and then with an excess of ArCH(2)N(3), afforded benzyl azide complexes [IrCl(2)(eta(1)-N(3)CH(2)Ar)P(3)]BPh(4) (3, 4) [Ar = C(6)H(5), 4-CH(3)C(6)H(4); P = P(OEt)(3), PPh(OEt)(2)]. Azide complexes reacted in CH(2)Cl(2) solution, leading to the imine derivative [IrCl(2){eta(1)-NH=C(H)C(6)H(5)}P(3)]BPh(4) (5). The complexes were characterized by spectroscopy and X-ray crystal structure determination of [IrCl(2)(eta(1)-N(3)CH(2)C(6)H(5)){P(OEt)(3)}(3)]BPh(4) (3a) and [IrCl(2){eta(1)-NH=C(H)C(6)H(5)}{P(OEt)(3)}(3)]BPh(4) (5a). Both solid-state structure and (15)N NMR data indicate that the azide is coordinated through the substituted Ngamma [Ir]-Ngamma(CH(2)Ar)NNalpha nitrogen atom.     

An unusual reaction of azide with nitroolefins

The reaction of sodium azide in DMSO with 9-dinitromethylenefluorene (DNF) and 9-bromonitromethylenefluorene (BNF) results in the formation of N-cyano-9-iminofluorene ($\text{2}$). The overall reaction time is two minutes at room temperature.     

Nickel azide photolysis

Photolysis of anhydrous NiN₆ at 30° under the action of high pressure Hg arc is reported. The sample for photolysis studies is prepared by treating aqueous nickel azide solution with excess of AnalaR dimethyl ketone. The pressure of N developed during photolysis under steady state conditions at constant intensity is a linear function oft ^1/2 and dark rate analysis suggests that the dependence ont ^1/2 should be due to the diffusion of N from reaction site to the surface of solid azide. Absence of photoconduction in the wavelength range of the irradiating radiation suggests that excitons are the reactive species and the linear dependence of the rate of photolysis on intensity is interpreted in terms of the reaction of a trapped exciton with adjacent azide ion.The authors are thankful to Mr. Etim, E. S. for technical assistance and to University of Calabar, Calabar, C.R.S., Nigeria for financial support.     

Linking cyano-bridged ladders by azide to form a layered metamagnet

Cyano-bridged corrugated ladder-like chains are connected by mu(1,1)-N(3) (end-on, EO) bridges to form a layered coordination polymer, [Mn(N(3))(CH(3)OH)[Cr(phen)(CN)(4)].CH(3)OH (2), which is the first mixed cyano-azide bridged compound, and shows metamagnetism below 21.8 K, a temperature much higher than that (3.4 K) of the crossed double chain [Cr(phen)(CN)(4)](2) [Mn(H(2)O)(2)].4H(2)O (1) based on the same building block [Cr(phen)(CN)(4)](-).     

Organic azide inhibitors of cysteine proteases

Cysteine proteases are crucial regulatory enzymes in human physiology and disease. Inhibitors are usually designed with reactive electrophiles to covalently bond to the catalytic cysteinyl sulfur, and consequently they also indiscriminately interact with biological thiolates and other nucleophiles, leading to toxic side effects in vivo. Here we describe an alternative to using reactive electrophiles, demonstrating the use of a much less reactive azidomethylene substituent (-CH2-N3) that confers potent inhibition of cysteine proteases. This new approach resulted in potent, reversible, competitive inhibitors of caspase-1 (IC50 < 10 nM), with significant advantages over aldehydes such as high stability in vitro to thiols (10 mM dithiothreitol (pH 7.2), 20 mM glutathione (pH 7.2, 9, 11)) and aqueous media, as well as some highly desirable druglike features. It was also demonstrated that azides can be incorporated into inhibitors of other caspases (e.g. 3, 8) and cathepsins (e.g. K, S, B), indicating the versatility of this valuable new approach to cysteine protease inhibition.     

Synthesis and X-ray structure of 1,1-dimethylhydrazinium azide

1,1-Dimethylhydrazinium azide, [ (CH₃)₂NH–NH₂] [N₃], was prepared in high yield from 1,1-dimethylhydrazine and HN₃ in CH₂Cl₂ solution at −20°C. The new compound has been fully characterized by elemental analysis, multinuclear NMR (¹H, ¹³C, ¹⁴ N, ¹⁵ N) and vibrational spectroscopy (IR, Raman). The structure in the solid state was determined by a low temperature (173 K) single crystal X-ray diffraction analysis.     

Reactions of terminal polyynes with benzyl azide

Terminal di-, tri-, tetra-, and pentaynes substituted with a variety of functional groups react with benzyl azide in the presence of CuSO(4)·5H(2)O and ascorbic acid to give derivatives of 4-ethynyl-, 4-butadiynyl-, 4-hexatriynyl-, and 4-octatetraynyl-1,2,3-triazoles in moderate to good yields. These reactions appear to proceed regioselectively, and functionalization occurs exclusively at the terminal alkyne moiety. As well, no evidence of multiple azide additions to the polyyne framework is observed. X-ray crystallographic analysis of nine derivatives is used to document the regioselectivity of the reaction as well as outline structural characteristics of the 1,2,3-triazole products.     

A direct comparison of azide and nitrile vibrational probes

The synthesis of 2'-azido-5-cyano-2'-deoxyuridine, N(3)CNdU (1), from trityl-protected 2'-amino-2'-deoxyuridine was accomplished in four steps with a 12.5% overall yield. The IR absorption positions and profiles of the azide and nitrile group of N(3)CNdU were investigated in 14 different solvents and water/DMSO solvent mixtures. The azide probe was superior to the nitrile probe in terms of its extinction coefficient, which is 2-4 times larger. However, the nitrile IR absorbance profile is generally less complicated by accidental Fermi resonance. The IR frequencies of both probes undergo a substantial red shift upon going from water to aprotic solvents such as THF or DMSO. DFT calculations supported the hypothesis that the molecular origin of the higher observed frequency in water is primarily due to hydrogen bonds between the probes and water molecules.     

Photolysis of zinc azide in the solid state

The photolysis of anhydrous zinc azide prepared by (1) dehydration of Zn(N₃)₂·2H₂O and (2) precipitation by acetone from aqueous solution, under the action of high pressure mercury arc is reported here. The pressure of nitrogen developed during photolysis under steady-state conditions at constant intensity is a linear function of t^1/2 in both the samples. The rate of photolysis is a linear function of intensity at constant temperature. A detailed analysis of the dark rate suggests that the dependence on t^1/2 should be due to the diffusion of nitrogen from the reaction site to the surface of the solid azide. An appropriate mathematical analysis is presented. The linear dependence of the rate of photolysis on the intensity of irradiation is interpreted in terms of the reaction of a trapped exciton with an adjacent azide ion. Absence of any detectable photoconduction in the wavelength range of the irradiating radiation suggests that excitons are the most probable reactive species. The sample of zinc azide obtained by the first method decomposes faster than the other under identical conditions, and has a slightly lower energy of activation of 1.4 kcal/mole compared to 1.75 kcal/mole for the second. These differences are discussed in terms of the defect concentrations of the two azide samples.     

Thermal decomposition of zinc hydroxy azide

The isothermal decomposition of zinc hydroxy azides, Zn(OH)_2-x(N₃)_x: follows deceleratory kinetics throughout the temperature range studied. The initial part of the decomposition fits into unimolecular decay law, log (1-a) = -kt. The contracting volume law satisfactorily describes the data at higher degrees of decomposition. The maximum value ofa upto which the slow decomposition could be recorded was 0.75. The aged form of zinc hydroxy azide decomposes with much lower rates and slightly different topochemical characteristics. The decrease in the rate of decomposition on ageing has been attributed to the formation of carbonate on the surface of the compound during storage. The change in topochemical behaviour is traced to the reported layer structure of zinc hydroxy azide. The effect of pre-heating on subsequent thermal decomposition has also been discussed.     

Tricyclopentadienyluranium azide complexes

The synthesis and characterization of A(N₃), [Na(18-crown-6)] [A(N₃)], [A(N₃A][BPh₄], [Na(18-crown-6)] [A(N₃)A] and A(N₃)A [A = (C₅H₄SiMe₃)₃U] are reported.     

Hydrogen randomization in phenyl azide

The loss of both HCN and C₂H₂ from the phenyl nitrenium cation radical generated from 2,4,6-d₃-phenyl azide is preceded by H/D randomization.     

Defective dicubane-like tetranuclear nickel(II) cyanate and azide nanoscale magnets

Four tetrameric nickel(II) pseudohalide complexes have been synthesized and structurally, spectroscopically, and magnetically characterized. Compounds 1-3 are isostructural and exhibit the general formula [Ni(2)(dpk·OH)(dpk·CH(3)O)(L)(H(2)O)](2)A(2)·2H(2)O, where dpk = di-2-pyridylketone; L = N(3)(-), and A = ClO(4)(-) for 1, L = NCO(-) and A = ClO(4)(-) for 2, and L = NCO(-) and A = NO(3)(-) for 3. The formula for 4 is [Ni(4)(dpk·OH)(3) (dpk·CH(3)O)(2)(NCO)](BF(4))(2)·3H(2)O. The ligands dpk·OH(-) and dpk·CH(3)O(-) result from solvolysis and ulterior deprotonation of dpk in water and methanol, respectively. The four tetramers exhibit a dicubane-like core with two missing vertexes where the Ni(II) ions are connected through end-on pseudohalide and oxo bridges. Magnetic measurements showed that compounds 1-4 are ferromagnetic. The values of the exchange constants were determined by means of a theoretical model based on three different types of coupling. Thus, the calculated J values (J(1) = J(2), J(3), and D) were 5.6, 11.8, and 5.6 cm(-1) for 1, 5.5, 12.0, and 5.6 cm(-1) for 2, 6.3, 4.9, and 6.2 cm(-1) for 3, and (J(1), J(2), J(3), and D) 6.9, 7.0, 15.2, and 4.8 cm(-1) for 4.