高能量密度材料3,3′-偶氮-1,2,4,5-四嗪衍生物的分子设计

运用密度泛函理论(DFT)方法,计算系列3,3′-偶氮-1,2,4,5-四嗪衍生物的生成热.结果显示:—N3取代基在增加3,3′-偶氮-1,2,4,5-四嗪衍生物的生成热方面起了非常重要的作用.通过分析标题化合物的最弱键离解能发现:—NH2或—N3取代基非常有利于增加衍生物的热稳定性.计算的爆速(D)和爆压(p)数值表明:—NO2或—NF2取代基有利于提高3,3′-偶氮-1,2,4,5-四嗪衍生物的爆轰性能.综合爆轰性能和热稳定性的计算结果,3种3,3′-偶氮-1,2,4,5-四嗪衍生物可以作为潜在的品优高能量密度材料(HEDM)候选物.     

Theoretical studies on the heats of formation, detonation properties, and pyrolysis mechanisms of energetic cyclic nitramines

Density functional theory calculations were performed to find comprehensive relationships between the structures and performance of a series of highly energetic cyclic nitramines. The isodesmic reaction method was employed to estimate the heat of formation. The detonation properties were evaluated by using the Kamlet-Jacobs equations based on the theoretical densities and HOFs. Results indicate the N-NO(2) group and aza N atom are effective substituents for enhancing the detonation performance. All cyclic nitramines except C11 and C21 exhibit better detonation performance than HMX. The decomposition mechanism and thermal stability of these cyclic nitramines were analyzed via the bond dissociation energies. For most of these nitramines, the homolysis of N-NO(2) is the initial step in the thermolysis, and the species with the bridged N-N bond are more sensitive than others. Considering the detonation performance and thermal stability, twelve derivatives may be the promising candidates of high energy density materials (HEDMs). The results of this study may provide basic information for the further study of this kind of compounds and molecular design of novel HEDMs.     

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.     

Cyclization Triggered by Deprotonation: The Gas‐Phase Acidity of 1,8‐Chalcogen‐Bridged Naphthalenes

High‐level density functional theory computations have been used to estimate the gas‐phase (intrinsic) acidities of the complete series of 1,8‐chalcogen‐bridged naphthalene derivatives. The existence of a chalcogen? chalcogen bond in chalcogen‐bridged naphthalene derivatives plays a crucial role in the intrinsic acidity of the system. For 1,8‐naphthalenediylbis(oxy), where this bond does not exist, the para C? H group is the most acidic site, whereas for the remaining compounds, deprotonation of the ortho CH groups is the most favorable process. Deprotonation of the aromatic rings has a large effect on the strength of the bonds of the five‐membered ring. These effects depend on the nature of the heteroatoms forming the X? Y bridge, and modulate the acidity of the molecule. Also importantly, when one of the heteroatoms is oxygen, ortho and para deprotonation lead to cleavage of the X? Y bridge. This bond fission favors the formation of a CYC (Y=S, Se, Te) three‐membered ring that enhances the stability of the anion and, therefore, increases the acidity of these compounds. We have shown that, whereas this cyclization process is energetically favorable for oxygen‐containing compounds, it is not favorable for the remaining derivatives.     

New theoretically predicted RDX‐ and β‐HMX‐based high‐energy‐density molecules

Theoretically new high‐energy‐density materials (HEDM) in which the hydrogens on RDX and β‐HMX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine and octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine, respectively) were sequentially replaced by (N NO₂)x functional groups were designed and evaluated using density functional theory calculations in combination with the Kamlet–Jacobs equations and an atoms‐in‐molecules (AIM) analysis. Improved detonation properties and reduced sensitivity compared to RDX and β‐HMX were predicted. Interestingly, the RDX and β‐HMX derivatives having one attached N NO₂ group [RDX‐(NNO₂)1 and HMX‐(NNO₂)1] showed excellent detonation properties (detonation velocities: 9.529 and 9.575 km·s⁻¹, and detonation pressures: 40.818 and 41.570 GPa, respectively), which were superior to the parent compounds. Sensitivity estimations obtained by calculating impact sensitivities and HOMO‐LUMO gaps indicated that RDX‐(NNO₂)1 and HMX‐(NNO₂)1 were less stable than RDX and HMX but more stable than any of the other derivatives. This method of sequential NNO₂ group attachment on conventional HEDMs offers a firm basis for further studies on the design of new explosives. Furthermore, the newly found structures may be promising candidates for better HEDMs.     

Theoretical studies on heats of formation,detonation properties,and bond dissociation energies of monofurazan derivatives

The heats of formation (HOFs) for a series of monofurazan derivatives were calculated by using density functional theory. It is found that the ? CN or ? N₃ group plays a very important role in increasing the HOF values of the furazan derivatives. The detonation velocities and detonation pressures of the furazan derivatives are evaluated at two different levels. The results show that the ? NF₂ group is very helpful for enhancing the detonation performance for the furazan derivatives, but the case is quite the contrary for the ? CH₃ group. An analysis of the bond dissociation energies and bond orders for the weakest bonds indicate that the substitutions of ? CN group are favorable and enhances the thermal stability of the furazan derivatives, but the ? NO₂ groups produce opposite effects. These results provide basic information for the molecular design of novel high‐energy density materials. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

3‐(p‐Chloro­phenyl)‐4‐phenyl‐4,5‐di­hydro­isoxazole‐5‐spiro‐2′‐1′,2′,3′,4′‐tetra­hydro­naphthalen‐1′‐one

In the title compound, C₂₄H₁₈ClNO₂, the phenyl ring and the tetralone moiety are approximately orthogonal to the isoxazoline ring. The isoxazoline ring adopts an envelope conformation, while the cyclo­hexenone ring of the tetralone moiety has an intermediate sofa/half‐chair conformation. In this structure, one C—H?N intermolecular and two C—H?O intramolecular hydrogen bonds occur; the H?A distances are 2.60, and 2.35 and 2.57 Å, respectively. The mol­ecules are held together by an intermolecular C—H?N hydrogen bond, forming a one‐dimensional chain along the [100] direction.     

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.     

{μ‐N,N′‐Bis[3‐(dimethyl­amino)prop­yl]­oxamidato(2–)‐κ6N,N′,O′:N′′,N′′′,O}­bis­[(1H‐imidazole‐κN3)(methanol‐κO)copper(II)] bis­(perchlorate)

The structure of the title compound, [Cu₂(C₁₂H₂₄N₄O₂)(C₃H₄N₂)₂(CH₄O)₂](ClO₄)₂ or [Cu₂(dmoxpn)(HIm)₂(CH₃OH)₂](ClO₄)₂, where dmoxpn is the dianion of N,N′‐bis­[3‐(dimethyl­amino)prop­yl]oxamide and HIm is imidazole, consists of a centrosymmetric trans‐oxamidate‐bridged copper(II) binuclear cation, having an inversion centre at the mid‐point of the central C—C bond, and two perchlorate anions. The Cu^II atom has square‐pyramidal coordination geometry involving two N atoms and an O atom from the dmoxpn ligand, an N atom from an imidazole ring, and an O atom from a methanol mol­ecule. The crystal structure is stabilized by O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds and imidazole π–π stacking inter­actions to form a three‐dimensional supra­molecular array.     

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.     

(C‐rac‐5,5,7,12,12,14‐Hexamethyl‐1,4,8,11‐tetraazacyclotetradecane‐κ4N)(nicotinato‐O,O′)nickel(II) perchlorate

In the title compound, [Ni(C₆H₄NO₂)(C₁₆H₃₆N₄)]ClO₄, the macrocyclic unit adopts a folded conformation, allowing the two carboxyl O atoms to occupy two neighbouring coordination sites and thus form an additional four‐membered chelate ring. The less crowded side of the macrocycle (that with the two asymmetric C—H groups) is directed towards the nicotinate anion and the asymmetric C—CH₃ groups are directed away from it. The macrocyclic NH groups neighbouring the C—CH₃ groups are also directed away from the nicotinate anion, while those NH groups which are near to the geminal methyl groups are directed towards the nicotinate anion. Although the complex does not include water mol­ecules, three types of hydrogen bond were found, involving NH groups of the macrocyclic ligand, pyridine N atoms and O atoms of the perchlorate anions.     

Di‐μ‐methoxo‐bis({N,N′‐bis­[2‐(3,5‐di­methyl­pyrazol‐1‐yl)­ethyl]­amine‐κ3N}copper(II)) bis­(hexa­fluoro­phosphate)

The title compound, [Cu₂(C₁₄H₂₃N₅)₂(CH₃O)₂](PF₆)₂, has a doubly methoxo‐bridged centrosymmetric copper dimer cation involving two tridentate bis­(pyrazolyl)­amine ligands. The geometry of each Cu^II atom is a distorted square pyramid with two N atoms of the pyrazole in bis­[2‐(3,5‐di­methyl‐1‐pyrazolyl)­ethyl]­amine (bpea) and two μ₂‐bridging O atoms of the methoxo ligands forming the basal plane, and the amine N atom occupying the axial position. In the bridging plane, the Cu—O bond lengths are 1.940 (4) and 1.942 (4) Å, and the bond angles for O—Cu—O and Cu—O—Cu are 76.1 (2) and 103.9 (2)°, respectively. The Cu?Cu distance is 3.058 (1) Å. The central four‐membered ring lies on an inversion centre.     

Energetic N,N′‐Ethylene‐Bridged Bis(nitropyrazoles): Diversified Functionalities and Properties

A new class of N,N′‐ethylene‐bridged bis(nitropyrazoles) was synthesized and fully characterized. The highly efficient formation of the N,N′‐ethylene bridge was accomplished using dibromoethane and ammonium or potassium pyrazolate. Further functional‐group transformations of diaminobis(pyrazole) and dichlorobis(pyrazole) gave rise to diversified derivatives, including dinitramino‐, diazido‐ and hexanitrobis(pyrazole). Single‐crystal X‐ray diffractions were obtained for hexanitro and diazido derivatives to illustrate the structural characteristics. Heats of formation and detonation performance were calculated by using Gaussian 03 and EXPLO5 v6.01 programs, respectively. Because of the different functionalized groups, the impact and friction sensitivities of these new compounds range from insensitive to sensitive. Among them, the hexanitro derivative displays the most promising overall energetic properties (density (ρ)=1.84 g cm^?3; decomposition temperature (T_d)=250 °C; detonation pressure (P)=34.1 GPa; detonation velocity (v_D)=8759 m s^?1; impact sensitivity (IS)=25 J; friction sensitivity (FS)=160 N), which is competitive with those of 1,3,5‐trinitrotriazacyclohexane (ρ=1.80 g cm^?3; T_d=205 °C; P=35.0 GPa; v_D=8762 m s^?1; IS=7 J; FS=120 N).     

3′,4′‐Bis(4‐chloro­phenyl)­spiro­[chroman‐3,5′(4′H)‐isoxazol]‐4‐one

The title compound, C₂₃H₁₅Cl₂NO₃, crystallizes with two independent mol­ecules in the asymmetric unit. The chroman­one moiety consists of a benzene ring fused with a six‐membered heterocyclic ring which adopts a sofa conformation. The five‐membered spiro­isoxazoline ring is in an envelope conformation. The p‐chloro­phenyl rings bridged by the five‐membered ring are nearly perpendicular to each other. The chromanone moiety of one mol­ecule packs into the cavity formed by the p‐chloro­phenyl rings of a second mol­ecule through the formation of C—H?π interactions. The structure is stabilized by weak C—H?O, C—H?Cl and C—H?π interactions.     

Synthesis and Properties of 2,3‐Dihydro‐1H‐corannuleno[2,3‐cd]pyridine (=2,3‐Dihydro‐1H‐dibenzo[1,10 : 6,7]fluorantheno[3,4‐cd]pyridine) Derivatives: Heterocyclic peri‐Anellated Corannulenes

The anellation of a 6‐membered ring to the 2,3‐position of corannulene (=dibenzo[ghi,mno]fluoranthene; 1 ) leads to curved aromatic compounds with a significantly higher bowl‐inversion barrier than corannulene (see Fig. 1). If the bridge is −CH₂−NR−CH₂−, a variety of linkers can be introduced at the N(2) atom, and the corresponding curved aromatics act as versatile building blocks for larger structures (see Scheme). The locked bowl, in combination with an amide bond (see 9 and 10 ), gives rise to corannulene derivatives with chiral ground‐state conformations, which possess the ability to adapt to their chiral environment by shifting their enantiomer equilibrium slightly in favor of one enantiomeric conformer. Rim annulation of corannulene seems to display a significantly lower electron‐withdrawing effect than facial anellation on [5,6]fullerene‐C₆₀‐I_h, as determined by an investigation of the basicity at the N‐atom of CH₂−NR−CH₂ (see 4 vs. 15 in Fig. 2).     

2‐Hydro­xy‐3‐(4,5,6,7‐tetra­hydro‐1H‐imidazo­[4,5‐c]­pyridin‐5‐ium‐4‐yl)­benzoate monohydrate

The title mol­ecule, C₁₃H₁₃N₃O₃·H₂O, is in the form of a mono­hydrated zwitterion. The tetra­hydro­pyridinium ring adopts an envelope conformation and is nearly coplanar with the plane of the imidazoline ring. The water solvate mol­ecule plays an important role as a bridge between zwitterions, forming molecular chains running along the c direction, which are interconnected by N—H?O hydrogen bonds into molecular ribbons. The crystal packing is further stabilized by another N—H?O and one O—H?N hydrogen bond, which interconnect the molecular ribbons.     

Influence of electronic effects from bridging groups on synthetic reaction and thermally activated polymerization of bisphenol‐based benzoxazines

Six bis‐benzoxazines based on bisphenols with different bridging groups, ? C(CH₃)₂? , ? CH₂? , ? O? , ? CO? , ? SO₂? , and single bond, were synthesized in toluene. The influence of electronic effects from bridging groups on ring‐forming reaction and thermal ring‐opening polymerization were relatively discussed in detail. Their structures were characterized by high‐performance liquid chromatography, Fourier transform infrared, ¹H NMR, differential scanning calorimetry, and elementary analysis. The quantum chemistry parameters of the bisphenols and bis‐benzoxazines were calculated by molecular simulation. The results indicated that the electron‐withdrawing groups inhibited the synthetic reaction by decreasing the charge density of α‐Cs of bisphenols and increasing energy barriers of the synthetic reactions. However, the electron‐withdrawing groups promoted the thermally activated polymerization, which resulted from their activation energy and curing temperature decrease by increasing the bond length and lowering the bond energy of C? O on oxazine rings. Besides, because of stronger electron‐withdrawing sulfone group, there were more arylamine methylene Mannich bridge structure in the polybenzoxazine. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

3‐Rhoda‐1,2‐diazacyclopentanes: A Series of Novel Metallacycle Complexes Derived From CN Functionalization of Ethylene

Rh‐containing metallacycles, [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NR)₂‐]Cl; TPA=N,N,N,N‐tris(2‐pyridylmethyl)amine have been accessed through treatment of the Rh^I ethylene complex, [(TPA)Rh(η²‐CH₂CH₂)]Cl ([ 1 ]Cl) with substituted diazenes. We show this methodology to be tolerant of electron‐deficient azo compounds including azo diesters (RCO₂N?NCO₂R; R=Et [ 3 ]Cl, R=iPr [ 4 ]Cl, R=tBu [ 5 ]Cl, and R=Bn [ 6 ]Cl) and a cyclic azo diamide: 4‐phenyl‐1,2,4‐triazole‐3,5‐dione (PTAD), [ 7 ]Cl. The latter complex features two ortho‐fused ring systems and constitutes the first 3‐rhoda‐1,2‐diazabicyclo[3.3.0]octane. Preliminary evidence suggests that these complexes result from N–N coordination followed by insertion of ethylene into a [Rh]?N bond. In terms of reactivity, [ 3 ]Cl and [ 4 ]Cl successfully undergo ring‐opening using p‐toluenesulfonic acid, affording the Rh chlorides, [(TPA)Rh^III(Cl)(κ¹‐(C)‐CH₂CH₂(NCO₂R)(NHCO₂R)]OTs; [ 13 ]OTs and [ 14 ]OTs. Deprotection of [ 5 ]Cl using trifluoroacetic acid was also found to give an ethyl substituted, end‐on coordinated diazene [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NH)₂‐]⁺ [ 16 ]Cl, a hitherto unreported motif. Treatment of [ 16 ]Cl with acetyl chloride resulted in the bisacetylated adduct [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NAc)₂‐]⁺, [ 17 ]Cl. Treatment of [ 1 ]Cl with AcN?NAc did not give the Rh?N insertion product, but instead the N,O‐chelated complex [(TPA)Rh^I ( κ²‐(O,N)‐CH₃(CO)(NH)(N?C(CH₃)(OCH?CH₂))]Cl [ 23 ]Cl, presumably through insertion of ethylene into a [Rh]?O bond.     

Synthesis,spectroscopic/electrochemical characterization and DNA interaction study of novel ferrocenyl‐substituted porphyrins

We report the synthesis and characterization of two new meso‐ferrocenylporphyrins, with the ferrocenyl unit attached at the para position of a C₆F₄ group by a C? N bond with ? NH(CH₂)₂NH? ( 2a ) and ? NH(CH₂)₄NH? ( 2b ) spacers. Compounds 2a and 2b were characterized through elemental analyses, electrospray ionization high‐resolution mass spectrometry, ¹H NMR, UV–visible and fluorescence spectroscopies, electrochemistry and spectroelectrochemistry. The free base porphyrin 2 was included for comparison purposes. The binding ability of 2 and the porphyrin derivatives 2a and 2b with calf thymus DNA was determined using UV–visible and fluorescence spectroscopies. The results suggest that the interaction of these systems most probably occurs through π‐stacking by non‐classical modes involving the partial insertion of the C₆F₅ ring between adjacent base pairs on DNA and possible hydrogen interaction with the aliphatic ? NH(CH₂)_nNH? (n = 2 or 4) groups with calf thymus DNA. Moreover, we also demonstrate that porphyrins generate singlet oxygen species and show good photostability after irradiation.     

Theoretical Investigation of 4,4′,6,6′‐Tetra(azido)azo‐1,3,5‐triazine‐N‐oxides and the Effects of N→O Bonding on Organic Azides

A family of 4,4′,6,6′‐tetra(azido)azo‐1,3,5‐triazine‐N‐oxides was designed and investigated by theoretical method. The effects of the N→O bond on the properties of TAAT‐N‐oxides, such as density, heat of formation, and detonation performance, were discussed. By comparison with the bond‐dissociation energy of the weakest bond and the electrostatic potentials, the effects of the N→O bond on the stability and impact sensitivity of organic azides were also discussed. The results show that the introduction of N→O bonds at the appropriate positions increases the oxygen balance and density of the compounds, while it has little effect on the stability and impact sensitivity. Consequently, their introduction results in energetic compounds with improved detonation performances.