Fu-de Ren

A theoretical study on unusual intermolecular T-shaped X–H...π interactions between the singlet state HB=BH and HF, HCl, HCN or H2C2

AbstractThe unusual T-shaped X–H...π hydrogen bonds are found between the B=B double bond of the singlet state HB=BH and the acid hydrogen of HF, HCl, HCN and H2C2 using MP2 and B3LYP methods at 6-311++G(2df,2p) and aug-cc-pVTZ levels. The binding energies follow the order of HB=BH...HF>HB=BH...HCl>HB=BH...HCN>HB=BH...H2C2. The hydrogen-bonded interactions in HB=BH...HX are found to be stronger than those in H2C=CH2...HX and OCB≡BCO...HX. The analyses of natural bond orbital (NBO) and the electron density shifts reveal that the nature of the T-shaped X–H...π hydrogen-bonded interaction is that much of the lost density from the π-orbital of B=B bond is shifted toward the hydrogen atom of the proton donor, leading to the electron density accumulation and the formation of the hydrogen bond. The atoms in molecules (AIM) theory have also been applied to characterize bond critical points and confirm that the B=B double bond can be a potential proton acceptor. The unusual T-shaped X–H...π hydrogen bonds are found between the B=B double bond of the singlet state HB=BH and the acid hydrogen of HF, HCl, HCN and H2C2

Theoretical insights into the structures and mechanical properties of HMX/NQ cocrystal explosives and their complexes, and the influence of molecular ratios on their bonding energies.

AbstractMolecular dynamics (MD) methods were employed to study the binding energies and mechanical properties of selected crystal planes of 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX)/nitroguanidine (NQ) cocrystals at different molecular molar ratios. The densities and detonation velocities of the cocrystals at different molar ratios were estimated. The intermolecular interaction and bond dissociation energy (BDE) of the N–NO2 bond in the HMX:NQ (1:1) complex were calculated using the B3LYP, MP2(full) and M06-2X methods with the 6-311++G(d,p) and 6-311++G(2df,2p) basis sets. The results indicated that the HMX/NQ cocrystal prefers cocrystalizing in a 1:1 molar ratio, and the cocrystallization is dominated by the (0 2 0) and (1 0 0) facets. The K, G, and E values of the ratio of 1:1 are smaller than those of the other ratios, and the 1:1 cocrystal has the best ductility. The N–NO2 bond becomes stronger upon the formation of the intermolecular H-bonding interaction and the sensitivity of HMX decreases in the cocrystal. This sensitivity change in the HMX/NQ cocrystal originates not only from the formation of the intermolecular interaction but also from the increment of the BDE of N–NO2 bond in comparison with isolated HMX. The HMX/NQ (1:1) cocrystal exhibits good detonation performance. Reduced density gradient (RDG) reveals the nature of cocrystallization. Analysis of the surface electrostatic potential further confirmed that the sensitivity decreases in complex (or cocrystal) in comparison with that in isolated HMX. Graphical AbstractBinding energies and mechanical properties of HMX/NQ cocrystals in different molecular molar ratios were studied using molecular dynamics methods. The origin of the sensitivity change in the HMX/NQ cocrystal originates from formation of intermolecular interactions and the bond dissociation energy increment of the N–NO2 bond

Theoretical insight into the binding energy and detonation performance of ε-, γ-, β-CL-20 cocrystals with β-HMX, FOX-7, and DMF in different molar ratios, as well as electrostatic potential

AbstractMolecular dynamics method was employed to study the binding energies on the selected crystal planes of the ε-, γ-, β-conformation 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (ε-, γ-, β-CL-20) cocrystal explosives with 1,1-diamino-2,2-dinitroethylene (FOX-7), 1,3,5,7-tetranitro- 1,3,5,7-tetrazacyclooctane with β-conformation (β-HMX) and N,N-dimethylformamide (DMF) in different molar ratios. The oxygen balance, density, detonation velocity, detonation pressure, and surface electrostatic potential were analyzed. The results indicate that the binding energies Eb* and stabilities are in the order of 1:1 > 2:1 > 3:1 > 5:1 > 8:1 (CL-20:FOX-7/β-HMX/DMF). The values of Eb* and stabilities of the energetic-nonenergetic CL-20/DMF cocrystals are far larger than those of the energetic-energetic CL-20/FOX-7 and CL-20/β-HMX, and those of CL-20/β-HMX are the smallest. For CL-20/FOX-7 and CL-20/β-HMX, the largest Eb* appears in the cocrystals with the 1:1, 1:2 or 1:3 molar ratio, and the stabilities of the cocrystals with the excess ratio of CL-20 are weaker than those in the cocrystals with the excess ratio of FOX-7 or β-HMX. In CL-20/FOX-7, CL-20 prefers adopting the γ-form, and ε-CL-20 is the preference in CL-20/β-HMX, and ε-CL-20 and β-CL-20 can be found in CL-20/DMF. The CL-20/FOX-7 and CL-20/β-HMX cocrystals with low molar ratios can meet the requirements of low sensitive high energetic materials. Surface electrostatic potential reveals the nature of the sensitivity change upon the cocrystal formation. Graphical AbstractMD method was employed to study the binding energies on the selected crystal planes in the ε-, γ-, β-CL-20 cocrystals with FOX-7, β-HMX and DMF in different molar ratios. Surface electrostatic potential reveals the nature of the sensitivity change in cocrystals.

A B3LYP and MP2(full) theoretical investigation into explosive sensitivity upon the formation of the molecule-cation interaction between the nitro group of 3,4-dinitropyrazole and H+, Li+, Na+, Be2+ or Mg2+.

AbstractThe explosive sensitivity upon the formation of molecule-cation interaction between the nitro group of 3,4-dinitropyrazole (DNP) and H+, Li+, Na+, Be2+ or Mg2+ has been investigated using the B3LYP and MP2(full) methods with the 6-311++G** and 6-311++G(2df,2p) basis sets. The bond dissociation energy (BDE) of the C3–N7 trigger bond has also been discussed for the DNP monomer and the corresponding complex. The interaction between the oxygen atom of nitro group and H+ in DNP…H+ is partly covalent in nature. The molecule-cation interaction and bond dissociation energy of the C3–N7 trigger bond follow the order of DNP…Be2+ > DNP…Mg2+ > DNP…Li+ > DNP…Na+. Except for DNP…H+, the increment of the trigger bond dissociation energy in comparison with the DNP monomer correlates well with the molecule-cation interaction energy, natural charge of the nitro group, electron density ρBCP(C3–N7), delocalization energy E(2) and NBO charge transfer. The analyses of atoms in molecules (AIM), natural bond orbital (NBO) and electron density shifts have shown that the electron density of the nitro group shifts toward the C3–N7 trigger bond upon the formation of the molecule-cation interaction. Thus, the trigger bond is strengthened and the sensitivity of DNP is reduced. FigureShifts of electron density as a result of formation of the complex. Purple regions denote gain, and yellow regions represent loss

A B3LYP and MP2(full) theoretical investigation into the strength of the C–NO 2 bond upon the formation of the intermolecular hydrogen-bonding interaction between HF and the nitro group of nitrotriazole or its methyl derivatives

AbstractThe changes of bond dissociation energy (BDE) in the C–NO2 bond and nitro group charge upon the formation of the intermolecular hydrogen-bonding interaction between HF and the nitro group of 14 kinds of nitrotriazoles or methyl derivatives were investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. The strength of the C–NO2 bond was enhanced and the charge of nitro group turned more negative in complex in comparison with those in isolated nitrotriazole molecule. The increment of the C–NO2 bond dissociation energies correlated well with the intermolecular H-bonding interaction energies. Electron density shifts analyses showed that the electron density shifted toward the C–NO2 bond upon complex formation, leading to the strengthened C–NO2 bond and the possibly reduced explosive sensitivity. FigureC1-N2 bond turns strong upon H-bond formation, leading to a possibly reduced explosive sensitivity

A theoretical prediction of the possible trigger linkage of CH3NO2 and NH2NO2 in an external electric field

AbstractThe effects of an external electric field on the C/N–NO2 bond with C/N–H and N–O bonds in CH3NO2 or NH2NO2 were compared using the DFT-B3LYP and MP2 methods with the 6-311++G(2d,p) and aug-cc-pVTZ basis sets. The results show that such fields have a minor effect on the C–N or C–H bond but a major effect on the N–O bond in CH3NO2, while in NH2NO2 electric fields affect the N–N bond greatly but the N–O or N–H bond only slightly. Thus, in CH3NO2, oxygen transfer or unimolecular isomerization to methyl nitrite might precede breaking of the C–N bond in the initial stages of decomposition, and the N–O bond could be the trigger bond in electric fields. In NH2NO2, however, N–N bond rupture may be preferential in an electric field and, consequently, the N–N bond might always be the real trigger bond. Atoms in molecules and natural bond orbital delocalization analyses, together with examination of shifts in electron density and frequencies support the above viewpoints. Forty-eight good linear correlations were found along the different field orientations at different levels of theory, including those between field strength (E) and changes in N−O/N−N bond length (ΔRN−O/N−N), ρ(N−O/N−N) values [Δρ(N−O/N−N), or stretching frequencies of the N−O/N−N bond (ΔυN−O/N−N). Graphical AbstractExternal electric fields have a major effect on the N–O or N–N bond inCH3NO2 or NH2NO2 , leading to a possible N–O trigger bond inCH3NO2 or a real N–N trigger bond in NH2NO2 in an electric field

A theoretical prediction of the relationships between the impact sensitivity and electrostatic potential in strained cyclic explosive and application to H-bonded complex of nitrocyclohydrocarbon

AbstractSeven models that related the features of molecular surface electrostatic potentials (ESPs) above the bond midpoints and rings, statistical parameters of ESPs to the experimental impact sensitivities h50 of eight strained cyclic explosives with the C–NO2 bonds were theoretically predicted at the DFT-B3LYP/6-311++G** level. One of the models was used to investigate the changes of h50 for the nitrocyclohydrocarbon frameworks in the H-bonded complexes of HF with nitrocyclopropane, nitrocyclobutane, nitrocyclopentane, and nitrocyclohexane. The results show that the correlation coefficients of the obtained models are small. When adding the effect of ring strain, the value of correlation coefficient is increased. According to the calculated h50, the sensitivities in the frameworks are increased after hydrogen bonding. As a global feature of molecules, surface electrostatic potential is more available to judge the sensitivity change than the trigger bond dissociation energy or ring strain energy in H-bonded complex. Graphical AbstractA theoretical prediction of the relationships between the impact sensitivity and electrostatic potential in strained cyclic explosive and application to H-bonded complex of nitrocyclohydrocarbonᅟ

A B3LYP and MP2(full) theoretical investigation into the strength of the C-NO2 bond upon the formation of the molecule-cation interaction between Na+ and the nitro group of nitrotriazole or its methyl derivatives

AbstractThe changes of bond dissociation energy (BDE) in the C–NO2 bond and nitro group charge upon the formation of the molecule-cation interaction between Na+ and the nitro group of 14 kinds of nitrotriazoles or methyl derivatives were investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. The strength of the C–NO2 bond was enhanced in comparison with that in the isolated nitrotriazole molecule upon the formation of molecule-cation interaction. The increment of the C–NO2 bond dissociation energy (ΔBDE) correlated well with the molecule-cation interaction energy. Electron density shifts analysis showed that the electron density shifted toward the C-NO2 bond upon complex formation, leading to the strengthened C-NO2 bond and the possibly reduced explosive sensitivity. FigureC1-N2 bond turns strong upon molecule-cation interaction formation, leading to a possibly reduced explosive sensitivity.

Can the positive aromatic ring be as π-electron donor in π-halogen bond? A MP2 theoretical investigation on the unusual π-halogen bond interaction between three-membered ring \left( {\hbox{BNN}} \right)_3^{+} and X1X2 (X1, X2 = F, Cl, Br)

AbstractThe unusual π-halogen bond interactions are investigated between