Roads to pentazolate anion: a theoretical insight.

The formation mechanism of pentazolate anion (PZA) is not yet clear. In order to present the possible formation pathways of PZA, the potential energy surfaces of phenylpentazole (PPZ), phenylpentazole radical (PPZ-R), phenylpentazole radical anion (PPZ-RA), PPZ and m-chloroperbenzoic acid (m-CPBA), p-pentazolylphenolate anion (p-PZPolA) and m-CPBA, and p-pentazolylphenol (p-PZPol) and m-CPBA were calculated by the computational electronic structure methods including the hybrid density functional, the double hybrid density functional and the coupled-cluster theories. At the thermodynamic point of view, the cleavages of C-N bonds of PPZ and PPZ-R need to absorb large amounts of heat. Thus, they are not feasible entrance for PZA formation at ambient condition. But excitation of PPZ and deprotonation of PPZ-RA probably happen before cleavage of C-N bond of PPZ at high-energy condition. As to the radical anion mechanism, the high accuracy calculations surveyed that the barrier of PZA formation is probably lower than that of dinitrogen evolution, but the small ionization potential of PPZ-RA gives rise to the unstable ionic pair of sodium PPZ at high temperature. In respect of oxidation mechanism, except for PPZ, the reactions of p-PZPolA and p-PZPol with m-CPBA can form PZA and quinone. The PZA formations have the barriers of about 20 kcal mol-1 which compete with the dinitrogen evolutions. The stabilities of PZA in both solid and gas phases were also studied herein. The proton prefers to transfer to pentazolyl group in the (N5)6(H3O)3(NH4)4Cl system which leads to the dissociation of pentazole ring. The ground states of M(N5)2(H2O)4 (M = Co, Fe and Mn) are high-spin states. The pentazolyl groups confined by the crystal waters in the coordinate compounds can improve the kinetic stability. As to the reactivity of PZA, it can be persistently oxidized by m-CPBA to oxo-PZA and 1,3-oxo-PZA with the barriers of about 20 kcal mol-1.

The sequential structure of tripyridiniumylporphyrin pendants in water-soluble copolymers and their association behaviour with tetrasulfonatophenylporphyrin guests: UV-vis absorption and fluorescence emission spectra study.

A novel cationic tripyridiniumylporphyrin monomer, 5-[4-[2-(acryloyloxy)ethoxy]phenyl]-l0,l5,20-tris(N-methyl-4-pyridiniumyl)porphyrinate zinc(ii) (ZnTrMPyP), was synthesized, and its self-aggregation in water was studied by UV-vis absorption. The monomer was copolymerized with acrylamide in water and DMSO, respectively, to prepare the water-soluble polymers P-W and P-D. The aggregation behaviour of the copolymers in aqueous solution was investigated by UV-vis absorption and fluorescence emission spectra. The polymer P-D displayed very similar absorption and emission spectra to those of ZnTrMPyP in water, indicating that the polymer chains in P-D have no significant effect on the aggregate structure of ZnTrMPyP in aqueous media. In comparison, two new absorption bands appeared in the Q band range of polymer P-W and its fluorescence spectra red shifted and the fluorescence quantum yield decreased obviously. These characteristics remained unchanged even in a good solvent for the monomer, suggesting that a new aggregation structure for the porphyrin pendants fixed by the covalent bond was formed. According to the different dispersed states of the porphyrin monomer in water and DMSO, the porphyrin pendants should distribute randomly in the P-D polymer chains while having micro-blocky sequences in polymer P-W. The association behaviour between the copolymers and tetra(p-sulfonatophenyl)porphyrin, TSPP, bearing opposite charged substituents were studied by absorption and emission Spectra and further analyzed by the Benesi-Hildebrand and the Stern-Volmer methods. The results showed that relatively discrete porphyrin pendants in P-D formed a 1 : 1 stoichiometric complex with TSPP and both static and dynamic mechanisms were active in this quenching process, while the tightly associated porphyrin pendants in P-W interacted with TSPP as an entirety and static quenching was dominant in this process. This observation was in accordance with their sequential structure. The polymer P-W has a wider absorption range and higher absorption intensity in the long wavelength region than the porphyrin monomer, which can more efficiently absorb light to accomplish light harvesting in water.

Study on the computer-aided design of high energetic compounds based on the 1,2,3,4-tetrazine-1,3-dioxide frame.

In order to discover more potential high energy compounds, five computer-aided design methods were founded, and 20 high energetic compounds based on the 1,2,3,4-tetrazine-1,3-dioxide frame were designed. The first step of computer-aided design methods was to design new frame M. Three combination rules were invented, they were simple double-points rule, complicated double-points rule, and complicated multi-points rule. The second step of computer-aided design methods was to design 1,2,3,4-tetrazine 1,3-dioxides derivants by connecting M to 1,2,3,4-tetrazine-1,3-dioxides. Two combination rules were invented, they were simple single-points rule and double-points rule. All the structures are ring-fused or caged compounds including 1,2,3,4-tetrazine-1,3-dioxide. In these compounds, almost half of them have positive or zero oxygen balances, and the nitrogen contents of 17 compounds are over 40%. The densities and detonation velocities of all compounds are over 1.98 g cm-3 and 9500 m s-1 respectively. -N = N- group and -NO2 group have a major contribution to enthalpy of formation, detonation heat, and power index. -O- group and -ONO2 group have the main contribution to density, detonation velocity, and detonation pressure.

Theoretical study of the effect of N-oxides on the performances of energetic compounds.

In order to study the effects of N-oxide on structure and performance, six categories of energetic compounds were systemically investigated. The results indicated that the C-C bonds in the rings were shortened, and the C-N bonds close to the N → O bond were elongated when N atoms was oxidized to form N → O bonds. N → O bonds can increase the densities of most categories of compounds, and the increment will increase with the number of N → O bonds. As to their detonation performances, almost all categories of compounds had an increased trend, except for some NO2-, NHNO2- and ONO2-substituted compounds. The contribution of 1,2,3,4-tetrazine and 1,2,4,5-tetrazine to performances was better than that of pyrazine and [1,2,5] oxadiazolo [3,4-b] pyrazine on the whole, and the groups, especially energetic groups, made a huge contribution to performance. When R was a NH2 or ONO2 group, all compounds had lower impact sensitivities, and thus represent candidates for novel energetic compounds. However, other than the sixth category of compounds, all compounds had higher impact sensitivities when R was a NO2 or NHNO2 group, and have little significance in application.

Experimental observation of TiN12+ cluster and theoretical investigation of its stable and metastable isomers.

TiN n+ clusters were generated by laser ablation and analyzed experimentally by mass spectrometry. The results showed that the mass peak of the TiN12+ cluster is dominant in the spectrum. The TiN12+ cluster was further investigated by photodissociation experiments with 266, 532 and 1064 nm photons. Density functional calculations were conducted to investigate stable structures of TiN12+ and the corresponding neutral cluster, TiN12. The theoretical calculations found that the most stable structure of TiN12+ is Ti(N2)6+ with Oh symmetry. The calculated binding energy is in good agreement with that obtained from the photodissociation experiments. The most stable structure of neutral TiN12 is Ti(N2)6 with D3d symmetry. The Ti-N bond strengths are greater than 0.94 eV in both Ti(N2)6+ and its neutral counterpart. The interaction between Ti and N2 weakens the N-N bond significantly. For neutral TiN12, the Ti(N3)4 azide, the N5TiN7 sandwich structure and the N6TiN6 structure are much higher in energy than the Ti(N2)6 complex. The DFT calculations predicted that the decomposition of Ti(N3)4, N5TiN7, and N6TiN6 into a Ti atom and six N2 molecules can release energies of about 139, 857, and 978 kJ mol-1 respectively.

Design and theoretical study of 15 novel high energy density compounds.

In order to seek the potential high energy density compounds (HEDCs) with excellent performance and satisfactory safety, some combination rules are presented and 15 HEDCs are designed and sifted, and followed by the properties predicting. From the results, HEDC-3, HEDC-4, HEDC-9, HEDC-10, HEDC-11, HEDC-12, HEDC-13, and HEDC-14 have good comprehensive properties. They are furoxan, fused ring or cage-type compounds, whose frame is composed of some single ring by single (double or multi) point addition. Their densities are over 1.95 g cm(-3), and detonation velocities are over 9500 m s(-1). Their BDEs are over 85 kJ mol(-1), and the values of available free space (∆V) are lower than the ∆V of ß-CL20 (∆V = 86). In view of the synthesis feasibility, the synthesis routes of HEDC-4, HEDC-9, HEDC-10, HEDC-12, HEDC-13, and HEDC-14 have been designed.

Theoretical study on the structure and stability of [1,2,5] oxadiazolo [3,4-e] [1,2,3,4]-tetrazine-4,6-Di-N-dioxide (FTDO).

Although many 1,2,3,4-tetrazine-1,3-dioxide derivates have been synthesized, [1,2,5] oxadiazolo [3,4-e] [1,2,3,4]-tetrazine-4,6-di-N-dioxide (FTDO) is the only one with high enthalpy of formation and high detonation velocity. Whereas, its stability has not been studied. In the present work, the structure of FTDO was investigated using density functional theory (DFT) method, and its stability was calculated by potential energy surface scanning and structure interconvert thermodynamics under different temperatures. The spontaneous isomerization of FTDO and its effect on the stability of FTDO were investigated. The dissociation of FTDO to N2, N2O and furoxan fragments was studied, and the possibility of synthetic route from FTDO to TTTO was discussed.