Wen-jing Shi

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 B3LYP and MP2(full) theoretical investigation on the cooperativity effect between hydrogen-bonding and cation-molecule interactions and thermodynamic property in the 1: 2 (Na+: N-(Hydroxymethyl)acetamide) ternary complex

AbstractThe cooperativity effects between the O/N–H∙∙∙O hydrogen-bonding and Na+∙∙∙O cation-molecule interactions in the 1: 2 (Na+: N-(Hydroxymethyl)acetamide) systems were investigated at the B3LYP/6-311++G**, MP2(full)/6-311++G** and MP2(full)/aug-cc-pvtz levels. The thermodynamic cooperativity calculations were also carried out for two pathways of the ternary-complex formation. The result shows that, in most ternary complexes, the O/N–H∙∙∙O and Na+∙∙∙O interactions are weakened in comparison with those in binary systems, leading to the anti-cooperativity effects, in particular in the complexes in which only the Na+∙∙∙O interactions exist. Shifts of electron density confirm the existence of anti-cooperativity. The increase of favorable enthalpic contribution leads to the positive cooperativity effect with negative ΔGcoop. on forming the ternary complex by initial N-(Hydroxymethyl)acetamide dimer followed by addition of Na+. In forming the ternary complex by Na+∙∙∙N-(Hydroxymethyl)acetamide with the second N-(Hydroxymethyl)acetamide unit, the large unfavorable entropy change leads to the negative cooperativity effect with positive ΔGcoop.. The ternary complex is more easily formed by the pathway in which Na+ binds to N-(Hydroxymethyl)acetamide dimer. FigureThermodynamic cooperativity effects in two pathways

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.

A theoretical investigation into the strength of N-NO2 bonds, ring strain and electrostatic potential upon formation of intermolecular H-bonds between HF and the nitro group in nitrogen heterocyclic rings C n H2n N-NO2 (n = 2-5), RDX and HMX.

AbstractChanges in N–NO2 bond strength, ring strain energy and electrostatic potential upon formation of intermolecular H-bonds between HF and the nitro group in nitrogen heterocyclic rings CnH2nN–NO2 (n = 2–5), RDX and HMX were investigated using DFT-B3LYP and MP2(full) methods with the 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. Analysis of electron density shifts was also carried out. The results indicate that H-bonding energy correlates well with the increment of ring strain energy. Upon complex formation, the strength of the N–NO2 trigger-bond is enhanced, suggesting reduced sensitivity, while judged by the increased ring strain energy, sensitivity is increased. However, some features of the molecular surface electrostatic potential, such as a local maximum above the N−NO2 bond and ring, σ+2 and electrostatic balance parameter ν, remain essentially unchanged upon complex formation, and only a small change in the impact sensitivity h50 is suggested. It is not sufficient to determine sensitivity solely on the basis of trigger bond or ring strain; as a global feature of a molecule, the molecular surface electrostatic potential is available to help judge the change of sensitivity in H-bonded complexes. Graphical AbstractThe strengthened N–NO2 bond suggests reduced sensitivity, while it is reverse by theincreased ring strain energy upon the complex formation. However, the molecular surfaceelectrostatic potential (VS) shows the little change of h50. The VS should be taken into accountin the analysis of explosive sensitivity in the H-bonded complex.

A theoretical study on the strength of the C-NO2 bond and ring strain upon the formation of the intermolecular H-bonding interaction between HF and nitro group in nitrocyclopropane, nitrocyclobutane, nitrocyclopentane or nitrocyclohexane.

AbstractAs a follow-up to our investigation into the influence of H-bond on the C–NO2 trigger bond, a comparison of the effect of the H-bond on the ring strain energy with the C–NO2 bond dissociation energy was carried out in the HF complex with nitrocyclopropane, nitrocyclobutane, nitrocyclopentane, and nitrocyclohexane by using the DFT-B3LYP and MP2 (full) methods with the 6–311++G(2df,2p) and aug-cc-pVTZ basis sets. The C–NO2 bond length decreases with strengthening of trigger-bond while the ring perimeter increases companied by weakening of ring strain upon the complex formation. The H-bonding energy correlates well with the increment of ring perimeter and the change of ring bond angle. For nitrocyclopropane∙∙∙HF, the effect of H-bond on the ring strain energy is notable, while for the other complex, it is negligible. Therefore, for nitrocyclopropane∙∙∙HF, the origin of the change of explosive sensitivity might be due to the increment of the C–NO2 bond dissociation energy and decrease of the ring strain energy, while for the other complex, it might be only due to the strengthening of C–NO2 bond. The analysis of electron density shifts shows that the C–C bond in ring loses density while the C–NO2 bond gains density, leading to the weakened ring strain and strengthened C–NO2 bond, and thus the possibly reduced explosive sensitivity. Graphical AbstractFor the nitrocyclopropane complex with HF, the origin of sensitivity change is due to the increment of the BDE in C-NO2 bond and decrease of the ring strain energy, while for the other complex it is only due to the strengthening of C-NO2 bond.

A B3LYP and MP2(full) theoretical investigation into cooperativity effects, aromaticity and thermodynamic properties in the Na+⋯benzonitrile⋯H2O ternary complex

AbstractThe cooperativity effects between H-bonding and Na+⋯π or Na+⋯σ interactions in Na+⋯benzonitrile⋯H2O complexes were investigated using the B3LYP and MP2(full) methods with 6-311++G(2d,p) and aug-cc-pVTZ basis sets. The thermodynamic cooperativity and the influence of this cooperativity on aromaticity was evaluated by nucleus-independent chemical shifts (NICS). The results showed that the influence of the Na+⋯σ or Na+⋯π interaction on the hydrogen bond is more pronounced than that of the latter on the former. The cooperativity effect appeared in the Na+⋯σ interaction complex while the anti-cooperativity effect tended to be in the Na+⋯π system. The change in enthalpy is the major factor driving cooperativity. Thermodynamic cooperativity is not in accordance with the cooperativity effect evaluated by the change of interaction energy. The ring aromaticity of is weakened while the bond dissociation energy (BDE) of the C–CN bond increases upon ternary complex formation. The cooperativity effect (Ecoop) correlates with Rc (NICS(1)ternary/NICS(1)binary) and ΔΔδ (Δδternary − Δδbinary) involving the ring and C ≡ N bond, as well as RBDE(C–CN) [BDE(C–CN)ternary/BDE(C–CN)binary], respectively. AIM (atoms in molecules) analysis confirms the existence of cooperativity. Probing the influences of cooperativity on aromaticity and thermodynamic properties

A B3LYP and MP2(full) theoretical investigation into the cooperativity effect between dihydrogen-bonding and H-M∙∙∙π (M = Li, Na, K) interactions among HF, MH with the π-electron donor C2H2, C2H4 or C6H6.

AbstractThe DFT-B3LYP/6-311++G(3df,2p) and MP2(full)/6-311++G(3df,2p) calculations were carried out on the binary complex formed by HM (M = Li, Na, K) and HF or the π-electron donor (C2H2, C2H4, C6H6), as well as the ternary system FH∙∙∙HM∙∙∙C2H2/C2H4/C6H6. The cooperativity effect between the dihydrogen-bonding and H–M∙∙∙π interactions was investigated. The result shows that the equilibrium distances RH∙∙∙H and RM∙∙∙π in the ternary complex decrease and both the H∙∙∙H and H–M∙∙∙π interactions are strengthened when compared to the corresponding binary complex. The cooperativity effect of the dihydrogen bond on the H–M∙∙∙π interaction is more pronounced than that of the M∙∙∙π bond on the H∙∙∙H interaction. Furthermore, the values of cooperativity effect follow the order of FH∙∙∙HNa∙∙∙π > FH∙∙∙HLi∙∙∙π > FH∙∙∙HK∙∙∙π and FH∙∙∙HM∙∙∙C6H6 > FH∙∙∙HM∙∙∙C2H4 > FH∙∙∙HM∙∙∙C2H2. The nature of the cooperativity effect was revealed by the analyses of the charge of the hydrogen atoms in H∙∙∙H moiety, atom in molecule (AIM) and electron density shifts methods. FigureShifts of electron density upon ternary-complex formation indicate the cooperativity effect between the dihydrogen-bonding and H–M∙∙∙π interactions