Inorganic Azides Research Articles

Click-Chemistry-Based Free Azide versus Azido Sugar Detection Enables Rapid In Vivo Screening of Glycosynthase Activity.

Engineering of carbohydrate-active enzymes such as glycosynthases to enable chemoenzymatic synthesis of bespoke oligosaccharides has been limited by the lack of suitable ultrahigh-throughput screening methods capable of robustly detecting either starting substrates or end-products of the glycosidic bond formation reaction. Currently, there are limited screening methods available for rapid and highly sensitive single-cell-based screening of glycosynthase enzymes employing azido sugars as activated donor glycosyl substrates. Here, we report a fluorescence-based approach employing click-chemistry for the selective detection of glycosyl azides as substrates versus free inorganic azides as reaction products that facilitated an ultrahigh-throughput in vivo single-cell-based assay of glycosynthase activity. This assay was developed based on the distinct differences observed in relative fluorescence intensity of the triazole-containing fluorophore product formed during the click-chemistry reaction of organic glycosyl azides versus inorganic azides. This discovery formed the basis for proof of concept validation of a directed evolution methodology for screening and sorting glycosynthase mutants capable of synthesis of targeted fucosylated oligosaccharides. Our screening approach facilitated fluorescence-activated cell sorting of an error-prone polymerase chain reaction-based mutant library of fucosynthases expressed in Escherichia coli to identify several novel mutants that showed increased activity for β-fucosyl azide-activated donor sugars toward desired acceptor sugars (e.g., pNP-xylose and lactose). Finally, we discuss avenues for improving this proof of concept in vivo assay method to identify better glycosynthase mutants and further demonstrate the broader applicability of this screening methodology for synthesis of bespoke glycans.

Azide Method for Generating Metal Vapors in Space

Modern methods of rocket research of the upper layers of the atmosphere and near-Earth space cannot be imagined without the use of glowing artificial clouds (GAC). Traditional pyrotechnic methods for generating vapors of alkali and alkaline earth metals, used for the formation of GAC in space, are ineffective and require, as a rule, the use of metals with high chemical activity. The article presents the results of studies on the development of an alternative method for generating vapors of alkali and alkaline earth metals to create GAC in near-Earth space using inorganic azides of the corresponding metals. The long-term use of pyrotechnic metal vapor generators to create GAC in the upper atmosphere, equipped with azide pyrotechnic compositions, confirmed their high efficiency, reliability and safety of use.

Structure-property correlation studies of alkaline-earth metal—azides M(N3)2 (M = Sr, Ba)

Inorganic metal azides M(N3)2 (M = Sr, Ba) and metal nitrates M(NO3)2 (M = Sr, Ba) are interesting materials due to their wide range of industrial usefulness as gas generators, pyrotechnics, photo graphic materials and explosives. In this work, we explore the mechanical, vibrational (infrared, phonon dispersion), Born effective charge (BEC) and thermodynamic properties of these materials to understand the sensitivity correlation studies using plane wave pseudopotential method. As these materials are layered with crucial non bonding interactions, the generalized gradient approximation with Tkatchenko–Scheffler (for Sr(N3)2) and Ortmann–Bechstedt–Schmidt (for Ba(N3)2) dispersion correction methods are adopted to compute accurate ground state properties with norm-conserving pseudopotentials. The calculated lattice parameters, unit cell volumes, bond lengths are well reproduced with 1% deviation when compared to the experimental and previously reported theoretical data. The mechanical (single crystal, poly-crystalline elastic constants) property correlations corroborate with the experimental impact sensitivity trend. The vibrational, phonon dispersion spectra’s, BEC’s, thermodynamic properties calculated with density functional perturbative theory approach provide better conclusions about the dynamical stability and polarization (optical sensitivity) trends. From the BEC results we propose that M(NO3)2 (M = Sr, Ba) materials may find various optical applications too. Overall, we tried to explain the crucial reasons for the differences in energetic properties of the studied materials.

Negative linear compressibility and structural phase transition in energetic silver azide under pressure: A first principles study

In this work, we have investigated high pressure behavior of silver azide within the framework of dispersion corrected density functional theory. We have predicted a pressure induced first order structural phase transition from orthorhombic (Ibam) → tetragonal (I4∕mcm) phase at 3.1 GPa. Ambient phase exhibits negative linear compressibility along a-axis in agreement with the experiments. Calculated phonon dispersion relations confirm the dynamical stability of ambient and high pressure phases. We have also analyzed bonding nature of alkali and transition metal azides, this provides an insight on possible correlation between structure-bonding-stability. The bonding nature between metal and terminal nitrogen of azide plays a predominant role in determining the order of stability in inorganic metal azides.

Trimethylsilyl-Induced N-O Bond Cleavage in Nitrous Oxide-Derived Aminodiazotates.

The chemical activation of nitrous oxide (N2O) typically results in O-atom transfer and the extrusion of N2 gas. In contrast, reactions of N-trimethylsilyl (TMS)-substituted amides with N2O give inorganic or organic azides, with concomitant formation of silanols or siloxanes. N-TMS-substituted amides are also able to induce N-O bond cleavage in N2O-derived dialkylaminodiazotates, generating tetrazene salts. These results indicate the potential of silyl groups in devising transformations, in which N2O acts as an N-atom donor.

Facile Quenching and Spatial Patterning of Cylooctynes via Strain-Promoted Alkyne-Azide Cycloaddition of Inorganic Azides.

Little is known about the reactivity of strain-promoted alkyne-azide cycloaddition (SPAAC) reagents with inorganic azides. We explore the reactions of a variety of popular SPAAC reagents with sodium azide and hydrozoic acid. We find that the reactions proceed in water at rates comparable to those with organic azides, yielding in all cases a triazole adduct. The azide ion's utility as a cyclooctyne quenching reagent is demonstrated by using it to spatially pattern uniformly doped hydrogels. The facile quenching of cyclooctynes demonstrated here should be useful in other bioorthogonal ligation techniques in which cyclooctynes are employed, including SPANC, Diels-Alder, and thiol-yne.

Pressure-Induced Amorphization of Strontium Azide

Strontium azide (Sr(N3)2) has been studied by in situ high pressure X-ray diffraction at room temperature. Sr(N3)2 exhibits anisotropic compressibility due to the orientation and rotation of azide anions. The refinement results and spectra measurements reveal that Sr(N3)2 possesses bent azide ions at ambient conditions, differing from the linear azide ions of alkali azides. The bent azide ions further bend and rotate with increasing pressure. These unique properties of bent azide ions play a significant role in the process of electron orbit hybridization and greatly enhance the propensity of nitrogen polymerization. The bulk modulus of Sr(N3)2 is 49.1 GPa, which is larger than those of alkali azides and close to those of heavy metal azides. The larger bulk modulus is attributed to the partial covalent bonding character of Sr(N3)2. Sr(N3)2 transforms into an amorphous phase at relative low pressure compared with alkali azide. This property might induce that Sr(N3)2 transforms into polymeric nitrogen more readily than other inorganic azides.

A metal-free turn-on fluorescent probe for the fast and sensitive detection of inorganic azides

Sodium azide is toxic and widely used in agricultural, commercial products, and research laboratories. Thus it is of a significant environmental concern and there is a need for the development of a rapid detection method. A fluorogenic dibenzylcyclooctyne derivative (Fl-DIBO) is herein described as a fluorescent probe for the rapid detection of inorganic azide via Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC). Fl-DIBO was found to be highly selective toward NaN3 in comparison to other common anions with good sensitivity and detection limit of 10μM.

Uranium(III) redox chemistry assisted by a hemilabile bis(phenolate) cyclam ligand: uranium-nitrogen multiple bond formation comprising a trans-{RN═U(VI)═NR}(2+) complex.

A new monoiodide U(III) complex anchored on a hexadentate dianionic 1,4,8,11-tetraazacyclotetradecane-based bis(phenolate) ligand, [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})I] (1), was synthesized from the reaction of [UI3(THF)4] (THF = tetrahydrofuran) and the respective potassium salt K2((tBu2)ArO)2Me2-cyclam and structurally characterized. Reactivity of 1 toward one-, two-, and four-electron oxidants was studied to explore the reductive chemistry of this new U(III) complex. Complex 1 reacts with one-electron oxidizers, such as iodine and TlBPh4, to form the seven-coordinate cationic uranium(IV) complexes [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})I][X] (X = I (2-I), BPh4 (2-BPh4)). The new uranium(III) complex reacts with inorganic azides to yield the pseudohalide uranium(IV) complex [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})(N3)2] (4) and the nitride-bridged diuranium(IV/IV) complex [(κ(4)-{((tBu2)ArO)2Me2-cyclam})(N3)U(μ-N)U(κ(5)-{((tBu2)ArO)2Me2-cyclam})] (5). Two equivalents of [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})I] (1) effect the four-electron reduction of 1 equiv of PhN═NPh to form the bis(imido) complex [U(κ(4)-{((tBu2)ArO)2Me2-cyclam})(NPh)2] (6) and the U(IV) species 2-I. Moreover, the hemilability of the hexadentate ancillary ligand ((tBu2)ArO)2Me2-cyclam(2-) allows to perform the reductive cleavage of azobenzene with an unprecedented formation of a trans-bis(imido) complex. The complexes were characterized by NMR spectroscopy, and all the new uranium complexes were structurally authenticated by single-crystal X-ray diffraction.

Theoretical studies of the structures and properties of (Br2InN3) n (n = 1–6) clusters

In an attempt to find single-source precursors, a series of small clusters of inorganic azides of indium (Br2InN3) n (n = 1–6) were studied using the dispersion correction density functional theory (wB97XD). The obtained (Br2InN3) n (n = 2–6) clusters have the core structures of 2n-membered ring with alternating indium and α-nitrogen atoms. The influences of cluster size (oligomerization degree n) on the structures, energies, IR spectra, and thermodynamic properties of clusters were discussed. The computed binding energies indicate the stability: 3A > 3B, 4B > 4C > 4A > 4D, 5E > 5D > 5B = 5C > 5A and 6I > 6C > 6D > 6G ≥ 6H > 6F > 6E > 6B > 6A. It is also found that (Br2InN3)2 and (Br2InN3)4 clusters possess higher stability than their neighbor sizes judged by the calculated second-order difference of energies (Δ2 E). Meanwhile, thermodynamic properties for (Br2InN3) n (n = 1–6) clusters increase with the increasing temperature and oligomerization degree n, and the oligomerizations are thermodynamically favorable at temperatures up to 800 K.

Two-dimensional ultrafast vibrational spectroscopy of azides in ionic liquids reveals solute-specific solvation.

The stereochemistry and the reaction rates of bimolecular nucleophilic substitution reactions involving azides in ionic liquids are governed by solute-solvent interactions. Two-dimensional ultrafast vibrational spectroscopy (2D-IR) shows that the picosecond dynamics of inorganic azides are substantially slower than organic azides in a series of homologous imidazolium ionic liquids. In water, both organic and inorganic azides spectrally diffuse with a ∼2 ps time constant. In the aprotic solvent tetrahydrofuran, both kinds of azides spectrally diffuse on a timescale >5 ps. In ionic liquids, like 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), organic azides spectrally diffuse with a 2-4 ps time constant, and inorganic azides spectrally diffuse with a >40 ps time constant. Such a striking difference suggests that neutral (organic) and charged (inorganic) azides are incorporated in the ionic liquids with different solvation structures.

High pressure Raman scattering and synchrotron X-ray diffraction studies of benzyl azide.

Benzyl azide was investigated by high-pressure Raman scattering spectroscopy and X-ray diffraction technologies. A complete vibrational analysis of benzyl azide was performed by combining the experimental measurements and theoretical calculations using DFT-based scaled quantum chemical approach. The high-pressure Raman spectra and calculation results indicate that benzyl azide underwent a conformational change at 0.67 GPa accompanied by rotation of methylene group and azide group. The frequency of the CH2 bending mode decreases with increasing pressure due to the increase of the C-H···π interactions, which is similar to the role of the hydrogen bond. A liquid to solid phase transition occurred at 2.7 GPa, which was confirmed by the X-ray diffraction measurements. As the pressure reached 25.6 GPa, all the azide group vibrations vanished, indicating that the decomposition pressure of the molecular azide groups in organic azides is lower than that of the azide ions in inorganic azides.

Development of “structure-property” models in nucleophilic substitution reactions involving azides

This paper reports a predictive model for the rate constant of the bimolecular nucleophilic substitution involving the azide moiety. It predicts reaction rate constants in different solvents, including organic mixtures, and with different organic and inorganic azides as reactants. The optimal descriptors describing solvent effects and a cation type in the azide salt were suggested. A reasonably good predictive performance of the model in cross-validation has been demonstrated. The model was applied to predict the rates of the reactions between sodium azide with two conformers of calixarenes as well as 3-bromopropyl phenyl ester. For sterically non-hindered molecules, a good agreement between predicted and experimental reaction rates was observed. On the other hand, the model poorly reproduces the results for sterically hindered molecules.

Structural Properties of Solid Energetic Materials: a Van Der Waals Density Functional Study

In the present work we have focused our attention towards the complete description of structural properties of energetic solids, namely inorganic azides, secondary explosives and oxidizers through density functional theory-based calculations. We find large deviations in structural parameters calculated with the standard exchange-correlation functional such as local density approximation and generalized gradient approximation (GGA). On the other hand, dispersioncorrected density functional of (GGA + G06) describes the crystal structure of the energetic solids with good accuracy. This leads to the fact that the dispersioncorrected density functionals are essential to describe the crystal structure and thereby the related physical and chemical properties of the energetic solids.

Synthesis of polynuclear azoles linked by ether tethers

Alkylation of NH-triazoles and tetrazoles and cycloaddition of organic and inorganic azides to propargyl ethers bearing a cyano group gave a number of polynuclear heterocyclic systems bridged by ether tethers.

Correlation of Structure and Sensitivity in Inorganic Azides III. A Mechanistic Interpretation of Impact Sensitivity Dependency on Non‐bonded Nitrogen to Nitrogen Distance

AbstractPreviously established correlations between impact sensitivity and minimum, non‐bonded, nitrogen to nitrogen distances in inorganic azides, imply that there must be a mechanism in operation, which can predict the non reaction of alkali metal azides and the violent decomposition of copper, silver, and lead azides. This paper examines the molecular orbitals used for bonding in the azides. The orbital energy level diagram indicates that the highest occupied molecular orbital, HOMO, are two, π type, non‐bonded orbitals, each occupied by an electron pair. The electron density lobes for these π type orbitals protrude into the space beyond both ends of the azide ion. These orbitals can overlap with ‘p’ and ‘d’ type orbitals on the metal cation, facilitating the transfer of the electron back to the metal cation; an integral part of the decomposition reaction. If an exciton is generated on the azide ion, the electron can migrate, via the extended three center MO, to the metal cation, leaving the positive hole on the terminal nitrogen atom. A similar hole on an adjacent azide, would allow the non‐bonding orbitals on each azide to interact. As the distance between neighboring azide ions decreases, it is postulated that these, non‐bonding, π type orbitals start to overlap and become bonding orbitals between adjacent azide ions. This process forms an unstable N6 moiety, which leads to the formation of three nitrogen molecules from two original azide ions. Thus, a feasible mechanism for the reaction can explain the observation that azides with non‐bonded nitrogen to nitrogen distances of >300 nm do not show impact sensitivity but, as this distance decreases below 300 nm, the sensitivity increases. The non impact sensitive azides could respond to thermal stimulus, which increases the thermal motion, thus reducing the critical nitrogen to nitrogen non‐bonded distance and reducing the energy for exciton production. Further work is required on the energy changes for such a reaction.

Correlation of Structure and Sensitivity in Inorganic Azides II. Effect of Lattice Defects on Non Bonded Nitrogen to Nitrogen Distances

AbstractThe sensitivity of explosives during handling operation is an important subject for explosives safety. Current ability to predict sensitivity is based on a series of empirical rules for different classes of explosive compounds based on their chemical composition. Whilst these may be valid for organic classes, inorganic materials do not conform to any of these patterns. There was a very good correlation found between impact sensitivity and the minimum non bonded nitrogen to nitrogen distance across a wide variety of azides. This correlation suggests reduction in the atomic movements required to produce the reaction products. This study examines the structure of a number of inorganic azides containing defects using molecular mechanics based on a Universal Force Field (UFF) approach, previously validated for a range of perfect lattices, with RMS deviations of between 7 and 11 pm from the original crystal structure following operation of the minimisation technique from a disordered arrangement.Using the UFF method, appropriate point defects (Schottky and Frenkel pairs) were modelled for these azides under conditions of maximum and minimum achievable pair separation. The maximum limit on pair separation was a result of the explicit modelling being limited to a 3×3×3 unit cell matrix. The results showed that the minimum non bond nitrogen to nitrogen distance narrowed in the presence of defects for all azides. In two cases, RbN3 and TlN3, this reduction in non bonded nitrogen to nitrogen distances was dramatically different from the other azides and was very dependant on the defect configuration and separation. This may indicate that the sensitivity of these two azides containing defects, is greater than the ideal crystal structure would suggest. If the normal production of this azide produces a significantly defective structure then it may well explain the enhanced sensitivity.

Facile derivatization of azide ions using click chemistry for their sensitive detection with LC-MS

By employing a click reaction, a novel method was developed for the sensitive detection of inorganic azides at as low as 21 ppb.

Correlation of Structure and Sensitivity in Inorganic Azides I Effect of Non‐Bonded Nitrogen Nitrogen Distances

AbstractSensitivity of explosives is a subject of keen interest to all those involved in the handling of these materials. Current ability to predict sensitivity is based on a series of empirical rules for different classes of explosive compounds and simple oxygen balance and the ratios of C and H to oxygen are typical empirical parameters. Whilst these may be valid for organic classes, many inorganic materials do not conform to any of these patterns. Inorganic azides do not have any C, H or O atoms so oxygen balance is irrelevant. Inorganic azides display a range of sensitivity from lithium azide, which is non‐energetic and insensitive, to copper(I) azide which is highly sensitive. A number of other parameters such as enthalpy of formation again do not provide a simple correlation with sensitivity.

Drophammer Test Investigations on Some Inorganic and Organic Azides

Drophammer Test Investigations on Some Inorganic and Organic Azides