Theoretical investigation on the impact sensitivity of tetrazole derivatives and their metal salts

The relative orders of impact sensitivity of tetrazole derivatives and their metal salts are investigated by examining the activation energy for forming azide in the process of thermal decomposition based on PM3-SCF-MO calculations. It is found that there is a parallel relationship between the activation energy and the sensitivity and a good linear relationship between the experimental impact sensitivity of metal salts of tetrazole and the reaction activation energy. It is shown that treating the metal salts of the tetrazole derivatives as the metal derivatives of tetrazole is meaningful.     

Decomposition Mechanism of 5,5′-Bis(tetrazole)-1,1′-dioIate(TKX-50) Anion Initiated by Intramolecular Oxygen Transfer

Density functional theory calculations at the B3LYP/6-31+G^** and B3LYP/6-311++G ^** levels were perfonned on thermal decomposition of 5,5′-bis(tetrazole)-1 ,r-diolate(TKX-50) anion with an intramolecular oxygen transfer being an initial step. Tlie results show that the intramolecular oxygen transfers are the rate-limiting steps for the decomposition of title anion with activation energies being in the range of 287-328 kJ/mol. Judged by the nucleus- independent chemical shift values, the formation of antiaromatic ring in transition state or the decrease of aromaticity of the tetrazole ring of the reactant makes somewhat contribution to the high potential energies of the rate-limiting transition states. However, the activation energies of the following N2 elimination tlirough various pathways are in a low range of 136-166 kJ/mol. The tetrazole ring acts as an electron donor or acceptor in difierent pathways to assist the bond nipture or group elimination. The rate constants in a temperature range of 500-2000 K for all the intramolecular oxygen transferring reactions were obtained. The corresponding linear relationships between InA and 1/T were established.     

Computational studies on tetrazole derivatives as potential high energy materials

The tetrazole is an important functionality of the most of energetic materials due to 80% nitrogen content, stability, and high enthalpy of formation. The present structure–property relationship study focuses on the optimized geometries of tetrazole derivatives obtained from density functional theory (DFT) calculations at B3LYP/6-31G* levels. The heat of formation (HOF) of tetrazole derivatives have been calculated by designing the appropriate isodesmic reactions. The increase in nitro groups on azole rings shows the remarkable increase in HOF. Density has been predicted by using CVFF force field. Increase in the nitro group increases the density. Detonation properties of the designed compounds were evaluated by using the Kamlet–Jacobs equation based on predicted densities and HOFs. Designed tetrazole derivatives show detonation velocity (D) over 8 km/s and detonation pressure (P) of about 32 GPa. Thermal stability was evaluated via bond dissociation energies (BDE) of the weakest C–NO₂ bond at B3LYP/6-31G* level. Charge on the nitro group has been used to assess the sensitivity correlation. Overall, the study implies that designed compounds of this series are found to be stable and expected to be the novel candidates of high energy materials (HEMs).     

Theoretical study addressing the effects of tautomerism and explicit/implicit water molecules on NQR and NMR parameters of tetrazole‐5‐thione

DFT/B3LYP calculations were employed to study the effects of tautomerism and explicit/implicit water molecules on Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) tensors of nitrogen nuclei in tetrazole‐5‐thione structure. The obtained results revealed that nuclear quadrupole coupling constant (χ) and isotropic chemical shielding (σ_iso) values of nitrogen nuclei in tetrazole ring of five possible tautomeric forms of tetrazole‐5‐thione, i.e. two thione forms called tautomers A and E and three thiol forms called tautomers B, C, and D, were functions of resonance energy(E₂) values of nitrogen lone pairs. Furthermore, it was observed that by increasing participation of lone pairs of nitrogen atoms in the ring resonance interactions, the σ_iso values around them were increased, while their χ and q_zz values were decreased. However, the results indicated that with exception of tautomer B, the order of q_zz and χ values of nitrogen nuclei in tetrazole ring was exactly opposite of the order of resonance energy values for the same nitrogen nuclei in all tautomers and their mono‐hydrated complexes. In addition, a significant decrease was noticed in χ and q_zz values when a water molecule was put in different positions near the tetrazole ring in tautomers A–E. The mentioned result can be attributed to hydrogen bond formation between nitrogen nuclei and the oxygen of water. In mono‐hydrated complexes, the σ_iso values around nitrogen atoms acting as hydrogen donors in hydrogen bond formation (N―H….OH₂) were decreased, while its values were increased for nitrogen atoms acting as hydrogen acceptors in hydrogen bond formation(N….H―OH). Copyright © 2016 John Wiley & Sons, Ltd.     

Water sorption and activation energy in polyimide thin films

The water sorption behavior and the activation energy were investigated for various chemical structure polyimide thin films; BPDA‐PDA, BPDA‐ODA, PMDA‐ODA, and 6FDA‐ODA. The activation energy for the water diffusion varied in the range of 5.53 to 9.27kcal/mol, and was in the increasing order: BPDA‐PDA < BPDA‐ODA < PMDA‐ODA < 6FDA‐ODA. BPDA‐PDA and BPDA‐ODA polyimide films showed relatively well‐ordered morphological structure, which results in relatively low diffusion coefficient and high activation energy. It was found that the diffusion coefficient and the activation energy are significantly related to the in‐plane orientation, crystallinity, and packing order in the polyimide thin films. The morphological structure was predominant factors for the water diffusion coefficient and activation energy in the polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2714–2720, 2000     

Density Function Theory Study on Effects of Different Energetic Substituent Groups and Bridge Groups on Performance of Carbon-Linked Ditetrazole 2N-Oxides

Based on the parent tetrazole 2N-oxide, six series of novel carbon-linked ditetrazole 2N-oxides with different energetic substituent groups (-NH₂, -N₃, -NO₂, NF₂, -NHNO₂) and energetic bridge groups (-CH₂-, -CH₂-CH₂-, -NH-, -N=N-, -NH-NH-) were designed. The overall performance and the effects of different energetic substituent groups and energetic bridge groups on the performance were investigated by density functional theory and electrostatic potential methods. The results showed that most of designed compounds have oxygen balance around zero, high heats of formation, high density, high energy, and acceptable sensitivity, indicating that tetrazole N-oxide is a useful parent energetic compound employed for obtaining high energy compounds, even only combined with some very common energetic substituent groups and bridge groups. Comprehensively considering the effects on energy and sensitivity, the -NO₂, -NF₂, -NH-and -NH-NH-are appropriate substituent groups for combining tetrozale N-oxide to design new energetic compounds, while -NH₂, -N₃, -CH₂-CH₂-, and -N=N-are inappropriate.     

Theoretical Study of Energetic Complexes (III): Bis‐(5‐nitro‐2H‐tetrazolato‐N2)tetraammine Cobalt(III) Perchlorate (BNCP) and Its Transition Metal (Ni/Fe/Cu/Zn) Perchlorate Analogues

The geometric conformation and electronic structure of bis‐(5‐nitro‐2H‐tetrazolato‐N²)tetraammine cobalt(III) perchlorate and its Ni/Fe/Cu/Zn analogues are studied under the TPSS (Tao‐Perdew‐Staroverov‐Scuseria) levels of density functional theory in order to throw light on the relationship between their energy gaps and impact sensitivity. While the perchlorate ions are coordinated with the copper cation, which is different from the other four compounds. NBO (Natural bond orbital) analyses indicated that the metal‐ligand interaction in the Co complex is covalent, while the others are ionic. The analysis of the electrostatic potential demonstrated that the O atoms from the nitro‐tetrazole ring and perchlorate were primarily negative, while the other atoms were positive. The study was also conducted to gain a better understanding of the correlation of the energy gap and impact sensitivity.     

Mechanisms of tetrazole formation by addition of azide to nitriles

It is well-known that azide salts can engage nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.     

Tetrazole Linkages as Photoactivated Fuels for Light-Regulated Photothermal/Photocatalytic Propulsion of Versatile Polymer Nanoplatforms

Colloidal motors with multimode propulsion have attracted considerable attention because of enhanced transportability. It is a great challenge to fabricate colloidal motors powered by a single engine for multimode synergistic propulsion. Herein, we report on Janus versatile polymer nanoplatforms integrating various functionalities via tetrazole linkages for light-regulated multimode synergistic propulsion in the liquid. The presence of tetrazole linkages in the polymers endows the nanoparticles with various photoresponsive capabilities. A sole energy source (ultraviolet or visible light) simultaneously activates photocatalytic N₂ release and photothermal conversion within the tetrazole-containing polymer phase at one side of asymmetric nanoparticles for converting light energy into photothermal/photocatalytic propulsion independent of the surrounding chemical medium. The photoactivated locomotion using tetrazoles as light-triggered fuels highly corresponds to light wavelengths, light powers and tetrazole contents. The tetrazole linkages capable of incorporating various functionalities to the polymer nanoparticles allow on-demand customizing of the colloidal motors, showing great potential in bio-applications.     

Synthesis, characterization and quantum chemistry study of 3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine

3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)- 1,2,4,5-tetrazine (BTATz) was synthesized by the condensation of triaminoguanidinium nitrate with 2,4-pentanedione, followed by oxidation and substitution reaction. The product was characterized by elemental analysis, IR, NMR spectrometry and DSC analysis. Instead of nitrogen dioxide/N-methylpyrrolidone, acetic acid/sodium nitrite was used as the oxidizer during the oxidation. Thus, the cost was reduced and the process was simplified. The theoretical properties of BTATz were estimated by a B3LYP method based on a 6-31G(d,p) basis set, and the stable geometric configuration and bond order were obtained. The vibrational frequencies, IR spectrum and thermodynamic properties under different temperatures were obtained from vibrational analysis and the relationship between temperature and thermodynamics properties was deduced. Pyrolysis mechanism of BTATz was discussedand the transition state and activation energy of ring opening reaction of the tetrazole were deduced. __________ Translated from Chinese Journal of Organic Chemistry, 2008, 28(3) (in Chinese)     

The Effectivity of 1H‐Triazoles and ‐Tetrazoles as Activators in Acid‐Catalyzed Phosphoramidite Alcoholysis

The efficiency of 5‐nitro‐1,2,4‐1H‐triazole ( 3 ), 5‐(methylthio)‐1H‐tetrazole ( 4 ), and 5‐(4‐nitrophenyl)‐1H‐tetrazole ( 5 ) as activators in phosphoramidite alcoholysis has been studied relative to 1H‐tetrazole ( 6 ). Reactions of these azoles with diisopropyl (diisopropylamido)phosphite ( 1a ) were followed in THF, and the rates were found to increase with increasing acidity of the azoles. The Brønsted α value of 0.7 determined for this dependence is in agreement with data published earlier.     

四唑衍生物异构化反应的理论研究

运用ＭＮＤＯＭＯ法对五种四唑衍生物的互变异构反应进行了理论计算,结果表明,过渡态的几何构型主要由迁移基团所决定,迁移基团的电性对反应速度影响很大,反应活化能与反应物中断裂键的键级和迁移基轩处净民荷之间均存在良好的线性关系,二取代基的性质均对反应平衡常数产生影响。     

顺反异构化对偶氮类含能化合物感度的影响

采用密度泛函理论的B3LYP/6-31G*方法优化了一些偶氮类含能化合物(偶氮苯衍生物、偶氮呋咱、偶氮三嗪和偶氮四嗪)的结构, 然后通过二阶微扰理论方法(MP2/6-31G*)进行单点能计算, 最后获得偶氮类含能化合物顺反异构体比较精确的相对能量. 结果发现, 偶氮类含能化合物的感度与其顺反异构体的相对能量有对应关系, 相对能量越大, 感度越低. 偶氮类含能化合物顺反异构体的相对能量可以作为评价其感度的指标之一. 通过分析偶氮类含能化合物顺反异构化过程对感度的影响机理, 提出偶氮类含能化合物具有自钝感特性.     

Theoretical study of the reaction mechanism of proton transfer in glycinamide

To investigate the tautomerism of glycinamide that is induced by proton transfer, we present detailed theoretical studies on the reaction mechanism of both the isolated gas phase and H₂O‐assisted proton transfer process of glycinamide, using density functional theory calculations by means of the B3LYP hybrid functional. Twenty‐six geometries, including 10 significant transition states, were optimized, and these geometrical parameters are discussed in detail. The relative order of the activation energy for hydrogen atom transfer of all the conformers has been systematically explored in this essay. For the amido hydrogen atom transfer process, the relative order of the activation energy is: IV < II < III < I, while in the carbonic hydrogen atom transfer process, the relative order is IV > II > III > I. Meanwhile, the most favorable structure for both the amido hydrogen atom transfer and the carbonic hydrogen atom transfer has been found. The involvement of the water molecule not only can stabilize the transition states and the ground states, but can also reduce the activation energy greatly. The superior catalytic effect of H₂O has been discussed in detail. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

3,6-双(1H-1,2,3,4-四唑-5-氨基)-1,2,4,5-四嗪的合成、表征及量子化学研究

以三氨基胍硝酸盐、戊二酮为起始原料, 经缩合、氧化、取代等反应合成了3,6-双(1H-1,2,3,4-四唑-5-氨基)-1,2,4,5-四嗪(BTATz), 并通过元素分析、红外、核磁、差示扫描量热法(DSC)等分析手段对其进行了表征. 采用亚硝酸钠/乙酸代替了二氧化氮/N-甲基吡咯烷酮, 改进了氧化步骤, 降低了成本, 简化了合成工艺. 用B3LYP方法, 在6-31G(d,p)基组水平上对其性能进行了计算, 得到了其稳定的几何构型和键级; 在振动分析的基础上求得体系的振动频率、IR谱及不同温度下的热力学性质, 并得到了温度对热力学性能影响的关系式; 探讨了其热解机理, 推断出四唑环开环时的过渡态和活化能.     

Synthesis and characterisation of tetra-tetrazole macrocycles

The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl-chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of the previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl-chain linker, the relative orientation of the tetrazole rings on the benzene ring and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene ring are prevented from becoming co-planar on intramolecular (steric) grounds. In the 1,3- and 1,4-bis(tetrazole)benzene derivatives, there is no such impediment, and a co-planar arrangement is observed where intra- and/or intermolecular stacking interactions exist. Deviations from co-planarity are associated with optimisation of intermolecular interactions between the tetrazole rings and adjacent alkyl chains. In the macrocycle based on 1,4-bis(tetrazole)benzene with four-carbon linkers, an intramolecular stacking interaction exists, which precludes the presence of any cavity. In the macrocycle based on 1,3-bis(tetrazole)benzene with six-carbon linkers, a cavity of 10.8×9.4 Å is observed for each molecule in the solid state, although the packing of adjacent molecules is such that there are no extended channels running through the crystal.     

Reaction of 2,4,6-triazido-1,3,5-triazine with triphenylphosphane. syntheses and characterization of the novel 2-triphenylphosphanimino-4-azidotetrazolo[5,1-a]-[1,3,5]triazine and 2,4,6,-tris(triphenylphosphanimino)-1,3,5-triazine

2-Triphenylphosphanimino-4-azidotetrazolo[5,1-a]-[1,3,5]triazine (6) was obtained by reaction of 2,4,6-triazido-1,3,5-triazine (1) with 1 equiv of triphenylphosphane. Raman and X-ray data revealed that only one azide group formed a tetrazole ring system whereas the second azide group did not undergo ring closure. To investigate the equilibrium between the tetrazole isomer and the open-chain azide structure for these and related species, (31)P NMR studies were carried out. The obtained spectra displayed an equilibrium between the tetrazole and the open-chain azide isomers. 2,4,6-Tris(triphenylphosphanimino)-1,3,5-triazine (4) was prepared by treatment of 1 with 3 equiv of triphenylphosphane, and its X-ray structure is discussed. On the basis of PM3 semiempirical and density functional calculations, the reaction of 1 with triphenylphosphane was studied. The thermodynamics of different isomerization reactions and the activation barriers to cyclization were estimated.     

A DFT study on the structure–property relationship of amino-, nitro- and nitrosotetrazoles, and their N-oxides: new high energy density molecules

We explore herein the structure, stability, heat of explosion, density, and the performance properties of amino, nitro, and nitroso substituted tetrazoles and their N-oxides using the density functional theory calculations at the B3LYP/aug-cc-pVDZ level. N-Nitro compounds have lower densities compared with those of C-nitrotetrazoles. Kamlet-Jacob semi-empirical equations were used to calculate the performance properties of designed compounds. The higher performance of tetrazole-N-oxides is due to their higher densities (2.110–2.287 g/cm³). Heat of explosion, stability, density and performance properties are related to the number and relative positions of NO₂, NH₂, and NO groups of the tetrazole ring. The designed molecules satisfy the criteria of high energy materials.     

Insertion reaction of propene into Rh?H bond in HRh(CO)(PH3)2(C3H6) compound: A density functional study

Quantum mechanical calculations at the MP4 (SDQ) level using the BP86‐optimized geometries were carried out to investigate the energies and reaction mechanism for the propene (CH₃ C¹H CH$^{\mathrm{2}}_{\mathrm{2}}$) insertion reaction into the Rh H bond, using the cis‐HRh(CO)(PH₃)₂ compound as a model catalytic species. Since the reaction may occur on the branched carbon 1 or in the normal carbon 2 , which leads to branched and normal Rh(alkyl) compounds, respectively, we investigated these two mechanisms. The results show that the insertion in the branched carbon has an activation energy of 16.2 kcal/mol, and the activation energy for the reaction to take place at the normal carbon is 14.3 kcal/mol. These activation energies, together with the calculated relative energy of the metal–alkyl compounds formed after the insertion considering these two pathways, were used to access the regioselectivity on this reaction. We found a ratio of normal‐ and iso‐products, n:iso, of (96:4), which is in excellent agreement with the experimental regioselectity of (95:5). © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 42–51, 2000     

甲苯定向硝化的理论研究

运用密度泛函理论(DFT)B3LYP方法，在6-31G~(* *)基组水平上，全优化计算 了硝酰阳离子NO_2~+对苯和从0-，m-,p-位进攻甲苯亲电取代硝化后应，求得4条反 应途径上包括反应物、过渡态和Wheland中间体共(4×3)12个反应驻点σ络合物的 分子几何、电子结构、能量和IR光谱等性质，阐明了反应中无同位素效应的实验事 实，求得各反应途径的活化能排序：p-＞o-＞PhH＞m-和σ络合物(R,TSak或INT)的 相对稳定化能排序：p-ArCH_3-NO_2~+＞o-ArCH_3-NO_2~+＞m-ArCH_3-NO_2~+＞ PhH-NO_2~+，从而阐明了甲基对苯环致活(或致钝)以及增加甲苯硝化络合物稳定性 的双重功能，对甲苯定向硝化的理论预示与实验结果相吻合。