N3 Bonds Research Articles

Ir(III)-catalyzed C(sp2)–H arylation and esterification cascade reaction of acrylic acids

A new catalytic protocol of Ir(III)-catalyzed C(sp2)–H arylation/esterification cascade reaction of acrylic acids with aromatic organoboron reagents has been disclosed herein. A wide range of substrates and coupling partners with excellent functional group tolerance could be suitable for this system. The resulting products containing 2-chloroethyl ester moiety could readily convert C–Cl bonds to C–I, C–N3 bonds, which will provide the possibility of the further application.

Organic–Inorganic Hybridization Engineering of Polyperylenediimide Cathodes for Efficient Potassium Storage

AbstractPolyperylenediimide (PDI) is always subject to its modest conductivities, limited reversible active sites and inferior stability for potassium storage. To address these issues, herein, we firstly propose an organic–inorganic hybrid (PDI@Fe‐Sn@N‐Ti3C2Tx), where Fe/Sn single atoms are bound to the N‐doped MXenes (N‐Ti3C2Tx) via the unsaturated Fe/Sn–N3 bonds, and functionalized with PDI via d–π hybridization, forming a high conjugated δ skeleton. The resulted hybrid cathode endowed with enhanced electronic/ionic conductivities, lowered dissociation barriers of multiple redox centers and a stable cathode electrolyte interphase layer displays a 14‐electron involved high‐rate capacities and long cycle life. Moreover, it shows competitive performance in full cells even under different folding states and low operating temperatures.

Decomposition mechanism on different surfaces of copper azide

Copper azide, a potential primary explosives that may replace traditional primers such as lead azide, mercury fulminate and silver azide, has received widespread attention, but its decomposition mechanism remains unclear. Here, based on first-principles calculations, (010)N3, (100)N3 and (001) facets with a copper/nitrogen atom ratio of 1/6 are found to be the most stable surfaces of copper azide crystal. Through transition state (TS) calculations, we find that during the decomposition process on the surface, there is a synergy effect between two Cu–N1–N2–N3 chains, where the terminal N2–N3 bonds on two chains break simultaneously, and the dissociated N3 atom bonds with another N3′ atom of adjacent chain to form a N2 molecule. Next, the Cu–N bond will rupture, and two more N2 molecules (N1–N2, N1′–N2′) desorb from the surface. The overall reaction releases above 4 eV energy at a barrier of 1.23 eV on (001) surface. Electronic structure calculations reveal that the TS of N2–N3 rupture is more stabilized than that of N1–N2. According to the above results, we propose a new decomposition mechanism based on simulations of N–N bond breaking on different surfaces of copper azide. The results underscore the surface effect in decomposition of energetic materials.

Rearrangement energies for radicals of azido nitroaromatic compounds

Dissociation energies of C–N3 bonds have been determined on the basis of data on the enthalpies of formation for a series of azido nitroaromatic compounds and the enthalpies of formation of radicals. Using fundamental relationships of chemical physics, a procedure has been suggested to calculate the energy of rearrangement of molecule fragments into radicals on the basis of special properties of rearrangement energy and the sums of average thermochemical energies for bonds comprising radical fragment in molecule. This calculation procedure provided a possibility to determine the energy of the N3 moiety transformation into N3 radical and the rearrangement energies of nitroaromatic radicals.

Ultrafast Nuclear Dynamics of Photoexcited Guanosine-5'-Monophosphate in Three Singlet States.

We report measurement of resonance Raman (RR) spectra of guanosine-5'-monophosphate (GMP), a DNA nucleotide at excitation wavelengths throughout its ππ* absorption band (Bb) in the 210-230 nm range. From these data, we constructed wavelength-dependent Raman intensity excitation profiles (REPs) for all observed modes. These profiles and the absorption spectrum were then modeled using self-consistent simulations based on the time-dependent wave packet propagation formalism. We inferred the initial structural dynamics of GMP immediately after photoexcitation in terms of dimensionless displacements. The simulations also provide linewidth-broadening parameters that in turn report on the time scale of dynamics. We compared deduced structural changes in the purine ring upon photoabsorption into the Bb state with those deduced for the two lowest lying ππ* (La and Lb at 280 and 248 nm, respectively) excited states of GMP. We find that excitation to the Lb state lengthens C6-N1 and C2═N3 bonds, which lie along the formation coordinate of various oxidative adducts but Bb excitation does not. We also find that photoabsorption by the Bb state weakens the C8-N9 bond and thus might assist imidazole ring opening via cleavage of the same bond. Electronic excitation to different ππ* states of the guanine chromophore results in contrasting structural changes; although absorption by the La and Lb states induces expansion of pyrimidine and contraction of imidazole rings, excitation results in overall shrinkage of both the rings. Computed absolute changes in internal coordinates imply that photoexcitation to any of the three singlet states of GMP does not lead directly to the formation of a cation radical of guanine.

The Importance of the Pauli Exchange-Type Repulsions and Hyperconjugative Interactions on the Conformational Properties of Halocarbonyl Isocyanates and Halocarbonyl Azides

To gain further insight into the origin of the anomeric relationships in planar open-chain (acyclic) compounds, we examined the effects of the hyperconjugative generalized anomeric effect (HC-GAE), Pauli exchange-type repulsion (PETR), the electrostatic model associated with the dipole–dipole interactions (EM-DDI), and the attractive electrostatic interactions (AEI) between the natural atomic charges (NACs) on the conformational properties of halocarbonyl isocyanates [halogen = F (1), Cl (2), Br (3)] and halocarbonyl azides [halogen = F (4), Cl (5), Br (6)] by means of G3MP2, CCSD, MP2, and B3LYP methods with the 6–311+G** basis set on all atoms and natural bond orbital interpretation. Importantly, the deletions of the through bond LPN3→σ*C2–X6 hyperconjugative interactions from the Fock matrices of the cis- and trans-conformations lead to the increase of the cis-conformations’ stability compared with their corresponding trans-conformations going from compound 1 to 3 and from compound 4 to 6, revealing the determining effects on the conformational preferences in compounds 1–3 and 4–6. Essentially, the effects of the through space (LPN3→σ*C4–O5 and LPNα→π*Nβ=Nω, respectively) hyperconjugative interactions on the conformational preferences in the isocyanate (1–3) and azide compounds (4–6) are negligible. The EM-DDI fails to account for the conformational preferences in compounds 2, 3, 5, and 6. Therefore, the generalized anomeric relationships in compounds 1–3 and 4–6 result from the cooperative effects of the HC-GAE and PETR. The variations of the AEIs revealed their opposite effects on the trend observed for the conformational preferences in compounds 1–3 and 4–6. Contrary to the usual assumption, the much larger barrier heights of the rotation around the C2–N3 bonds in the azide compounds (4–6) compared with those in the isocyanate compounds (1–3) result from the exchange components and have no hyperconjugative origin.

ChemInform Abstract: Taming Azide Radicals for Catalytic C—H Azidation

AbstractReview: 110 refs.

Taming Azide Radicals for Catalytic C–H Azidation

Reactions that directly transform aliphatic C–H bonds into alkyl azides are noticeably lacking in the repertoire of synthetic reactions, despite the importance of molecules containing C–N3 bonds in organic synthesis, chemical biology, and drug discovery. Harnessing the ubiquity of C–H bonds in organic molecules and the versatility of the azide functional group, such transformations could have broad applications in various disciplines. Radical C–H activation represents an appealing strategy to achieve aliphatic C–H azidation, as it overcomes many drawbacks of conventional organometallic approaches in activating inert aliphatic C–H bonds. Novel C–H azidation methodologies could be realized by combining radical C–H activation via hydrogen atom abstraction with suitable azide-transfer reagents. In this perspective, we survey the history of radical C–H azidation and summarize several significant recent advances in the field. All radical C–H azidations to date follow a general approach comprising an initial rad...

Structure and photochemistry of a saccharyl thiotetrazole.

The molecular structure and photochemistry of 5-thiosaccharyl-1-methyltetrazole (TSMT) were studied by means of matrix-isolation FTIR spectroscopy, X-ray crystallography, and theoretical calculations. The calculations predicted two conformers of TSMT that differ in energy by more than 15 kJ mol(-1). The infrared spectrum of TSMT isolated in solid argon was fully assigned on the basis of the spectrum calculated (O3LYP/6-311++G(3df,3pd)) for the most stable conformer. In the crystal, TSMT molecules were found to assume the same conformation as for the isolated molecule, with each molecule forming four hydrogen bonds with three neighboring molecules, leading to a network of TSMT oligomers. Upon UV (λ = 265 nm) irradiation of the matrix-isolated TSMT, two photodegradation pathways were observed, both arising from cleavage of the tetrazolyl ring. Pathway a involves cleavage of the N1-N2 and N3-N4 bonds with extrusion of N2, leading to photostable diazirine and thiocarbodiimide derivatives. The photostability of the photoproduced diazirine under the conditions used precluded its rearrangement to the nitrile imine, as reported for 5-phenyltetrazole by Bégué et al. ( J. Am. Chem. Soc. 2012 , 134 , 5339 ). Pathway b involves cleavage of the C5-N1 and N4-N3 bonds, leading to a thiocyanate and methyl azide, the latter undergoing subsequent fragmentation to give CNH.

A kinetic study of thermal decomposition of glycidyl azide polymer (GAP)-based energetic thermoplastic polyurethanes

Energetic thermoplastic polyurethane elastomers (ETPUs) of glycidyl azide polymer (GAP) were synthesized on GAP/poly(caprolactone)(PCL) (100/0, 50/50) as a soft segment and methylenebis(phenylisocyanate) (MDI) extended 1,5-pentanediol as a hard segment by solution polymerization in dimethyl formamide (DMF). Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) were used to examine the thermal decomposition behavior. Kinetic analysis was performed with model fitting and a model-free method to obtain the activation energy as a function of the extent of conversion. ETPU decomposition was divided into two stages with different activation energies. The first main weight loss step corresponds to the elimination of N2 from the decomposition of -N3 bonds within azide polymers. The activation energy of the main decomposition of GAP ETPU and GAP/PCL ETPU was approximately 190 kJ/mol. The second weight loss step coincides with the decomposition of the skeleton. The activation energy of those showed an increasing trend.

X-ray crystal structure of tetrakis(1-methylcytosine)copper(II) perchlorate dihydrate: effect of 1-methyl substitution on cytosine on the spectral and redox behaviour

Copper(II) tetrakis-complexes of cytosine (cyt), 1-methylcytosine (1-mcyt) and cytidine (cyd) have been isolated and their spectral and electrochemical properties investigated. The X-ray crystal structure of tetrakis(1-mcyt)copper(II) perchlorate dihydrate has been successfully determined. The co-ordination geometry around copper in the complex corresponds to square-based 4+4′ co-ordination. In addition to the preferential CuN3 bonds, there is significant interaction between copper(II) and the exocyclic O2 of 1-mcyt rings. The mutually cis 1-mcyt rings are present in a head-tail-head-tail arrangement, which is stabilised by a network of bifurcated hydrogen-bonding between the exocyclic amine hydrogen atoms and the oxygen atoms of the adjacent carbonyl groups. The aqueous solution spectra of the complexes are slightly different from solid state spectra revealing that the solid state structures undergo slight changes on dissolution in water. The electronic and EPR spectral and electrochemical results are consistent with the retention of the solid state structure even in solution. The EPR spectra exhibit N-superhyperfine lines corresponding to the coordination of four N3 atoms of cytosines. The higher g ‖ values indicate decreased covalency in the metalligand bond and the range of g ‖/ A ‖ quotient (119–121 cm) confirms the presence of CuN 4 square-planar co-ordination geometry even in solution. The plot of i pc and E 1/2 values versus 1-mcyt concentration for the electrochemical titration of Cu(ClO 4) 2 with 1-mcyt reveals an inflection point indicating the formation of 1:4 species in solution. The trend in E 1/2 values of the complexes shows that the incorporation of electron releasing methyl group/ribose moiety at N1 position of cytosine ring enhances the stabilisation of Cu(II), in spite of the steric demand from OC2.

Crystal structure and conformational analysis of 2-thioamide derivatives of thiazole

Molecular and crystal structures of two thioamide derivatives of thiazole were analysed based on X-ray diffraction data and results obtained from quantum chemistry (QC) and molecular mechanics (MM) calculations. It was found that within the thiazole rings, the S1–C2 bond appeared to be more affected by the action of two-substituents rather than the C2–N3 bonds. The ab initio calculations showed that the C2–C6 bond connecting the thioamide group with thiazole is shortened when both the systems are coplanar, but a conjugation is relatively weak and does not enforce such conformation. The QC and MM calculations indicated that the particular parts of the thioamide group may exist in two conformations. However, relatively high energy barrier excluded the possibility of change of one conformation into the other by simple rotation around the C2–C6 or C6–N8 bonds. Moreover, the MM calculations explained that steric hindrance is not the main reason of energy barrier for suggested rotations. The observed cis–trans conformation is stabilised by intramolecular hydrogen bonds.

Lewis Base Adduct Stabilized Organogallium Azides: Synthesis and Dynamic NMR Spectroscopic Studies of Novel Precursors to Gallium Nitride and Role of Ammonia as Reactive Carrier Gas

The organogallium azides (N3)2-a(R)aGa[(CH2)3NMe2]1-a (1a-c: R = CH3, tBu; a = 0, 1), (Et)(N3)2Ga (2a), and (Et)(N3)2Ga·L (2b−d: L = thf, H2NtBu, py, NC7H13) are quantitatively synthesized by salt metathesis from the chloro species (Cl)2-a(R)aGa[(CH2)3NMe2]1-a (a = 0, 1) or EtGaCl2 and sodium azide. The preferential ammonolysis of Ga−N3 bonds for [Et2Ga(N3)]3 (4) and 1 and 2 is demonstrated; e.g. the dimer Et2Ga(μ-NH2)(μ-N3)GaEt2 (3) was obtained. The characterization of these compounds by means of elemental analysis, 1H-, 13C-, 14N-, and 15N-NMR, MS, and infrared ν(N3) data is reported. The dynamics of the intramolecular Ga−N donor−acceptor bonded heterocycle and the azide group is discussed on the basis of variable-temperature NMR data. The barrier of activation of the bimolecular azide exchange process for (N3)2Ga[(CH2)3NMe2] (1c) amounts about 50 kJ·mol-1. The role of ammonia as reactive carrier gas for low-pressure metal organic chemical vapor deposition (MOCVD) of GaN with 1c as precursor is discu...

Combustion of energetic azide polymers

The combustion-wave structures of azide polymers were examined based on the data obtained by burningrate and temperature-profile measurements. The energetic azide polymer evaluated in this study was bis-azide methyl oxetan (BAMO), which contains two —N3 bonds in the molecular structure. BAMO polymer was copolymerized with tetrahydrofuran and cured with an isocyanate and cross-linked to formulate BAMO copolymer. The results indicate that the burning rate of BAMO copolymer increases with increasing the energy density contained within the unit mass of BAMO copolymer samples. The temperature sensitivity of burning rate is three or four times greater than that of conventional solid propellants. The rate of heat release in the gas phase increases as initial temperature increases at constant pressure. The heat transfer process in the combustion wave is correlated with the observed burning-rate characteristics.

Metal complexes of purine-N-oxides. II. The crystal structure of catena-μ-(4-aminoimidazole-5-carboxamidoxime) diaquo copper(II) sulphate trihydrate, a degradation product of adenine-N1-Oxide

[Cu(C4H7N5O)H2O)2SO4]·3H2O, monoclinic, space group Cc, a = 13.652(1) Å, b = 14.630(1) », c = 6.795(1) », β = 95.34(8)°, Z = 4. 1479 independent intensities above background were collected on a CAD-4 diffractometer using MoKα radiation. The structure was refmed by full-matrix least-squares to R = 0.016. Adenine-N1-oxide is degraded at a higher pH than expected when Cu ions are present. The degradation product is formed by scission of the C2N1 and C2N3 bonds. N1 is placed in a cis planar configuration to N7 by a rotation around the C5C6 bond, thus enabling N1, N7 equatorial chelation to copper, which has a 4 + 2 octahedral coordination. Two water molecules occupy the remaining equatorial positions, while the axial positions are occupied by a sulphate group and N3 of an adjacent ligand. The coordination bond lengths are CuN1 = 1.960 », CuN7 = 1.972 », CuO2 = 1.949 », CuO4 = 1.987 », CuO9 = 2.500 », CuN3 = 2.793 ».

Geometry and bonding of nitro- an azido-groups in palladium(II) four-co-ordinate complexes containing terdentate ligands

The crystal structures of the following palladium(II) complexes: (I)[NO2Pd(dien)]NO3, (II)[NO2Pd(Et4dien)]- NO3, and (III)[N3Pd(Et4dien)]NO3(dien = diethylenetriamine) have been determined by Patterson and Fourier methods. Crystal data are: (I), monoclinic, space group P21/c, Z= 4, a= 11.627(7), b= 7.617(6), c= 17·380(9)Å, β= 133.77(5)°: (II), orthorhombic, space group P212121, Z= 4, a= 21.825(9), b= 10.977(7), c= 8.233(6)Å; (III), orthorhombic, space group P212121, Z= 4, a= 20.167(9), b= 11.262(6). c= 8.644(6)Å. Anisotropic least-squares refinement reduced R to 0.034 (I) 0.052 (II), and 0.059 (III). The co-ordination geometry of the nitro-group is determined by the bulkiness of the terdentate ligand in such a way that NO2– is nearly parllel to the donar-atom plane in (I) and nearly normal to it in (II). A π contribution in the Pd–NO2 and Pd–N3 bonds seems to be excluded on the basis of structural parameters.