Aromatic hydrogenation is a challenging transformation typically requiring alkali or transition metal reagents and/or harsh conditions to facilitate the process. In sharp contrast, the aromatic heterocycle 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene is shown to be reduced under 4 atm of H2 to give [3.1.0]bicylo reduction products, with the structure of the major isomer being confirmed by X-ray crystallography. NMR studies show this reaction proceeds via a reversible 1,4-H2 addition to generate an intermediate species, which undergoes an irreversible suprafacial hydride shift concurrent with P-P bond formation to give the isolated products. Further, para-hydrogen experiments confirmed the addition of H2 to triphosphabenzene is a bimolecular process. Density functional theory (DFT) calculations show that facile distortion of the planar triphosphabenzene toward a boat-conformation provides a suprafacial combination of vacant acceptor and donor orbitals that permits this direct and uncatalyzed reduction of the aromatic molecule.

This Review focuses on the development of metal aminoboranes; it discusses their synthesis, structure, chemical characterization, and applications. The lightweight nature of the molecules, the simplified procedures for the synthesis of the target compounds, the reversibility of hydrogen storage and dehydrogenation, and in-depth research on the mechanism of the thermal decomposition are also discussed. A major challenge that still remains is how to combine the advantages of the compounds to produce a material that is not only able to release and absorb hydrogen under atmospheric conditions, but is also lightweight with a stable molecular structure. Finally, some future trends and perspectives in these research areas will be outlined.

We investigated 5,8-dinitro-5,6,7,8-tetrahydrotetrazolo[1,5-b][1,2,4]triazine (short for DNTzTr (1)) using various ab initio quantum chemistry methods. We proposed an additional three novel polynitro-substituted tetrazolotriazine-based compounds with exceptional performance, including 5,8-dinitro-5,6-dioxotetrazolo[1,5-b][1,2,4]triazine, DNOTzTr (2), 4,5,9,10-tetranitro[1,2,4,5]tetrazolo[3,4-b][1,2,4,5]tetrazolo[3',4':5,6]triazino[2,3-e]triazine, TNTzTr (3), and 4,5,6,10,11,12-hexanitro-bis[1,2,4,5]tetrazolo[3',4':5,6]triazino[2,3-b:2',3'-e]triazine, HNBTzTr (4). The optimized structure, electronic density, natural bond orbital (NBO) charges and HOMO-LUMO orbitals, electrostatic potential on surface of molecule, IR- and NMR-predicted spectra, as well as thermochemical parameters were calculated with the B3LYP/6-311+G(2d) level of theory. Critical parameters such as density, enthalpy of formation (EOF), and detonation performance have also been predicted. Characters with positive EOF (1386.00 and 1625.31 kJ/mol), high density (over 2.00 g/cm(3)), outstanding detonation properties (D = 9.82 km/s, P = 45.45 GPa; D = 9.94 km/s, P = 47.30 GPa), the perfect oxygen balance set to zero, and acceptable impact sensitivity led novel compounds 3 and 4 to be very promising energetic materials. This work provides the theoretical molecule design and a reasonable synthesis path for further experimental synthesis and testing.

Two novel compounds 5-(dinitromethylene)-1,4-dinitramino-tetrazole (DNAT) and 1,1'-dinitro-4,4'-diamino-5,5'-bitetrazole (DNABT) were suggested to be potential candidates of high energy density materials (HEDMs). The optimized geometry, NBO charges and electronic density, HOMO-LUMO, electrostatic potential on the surface of molecules, the IR spectrum and thermochemical parameters were calculated for inspecting the electronic structure properties at B3LYP/6-311++G** level of theory. Meanwhile, the solid states of DNAT and DNABT were studied using the crystal packing models by the plane-wave periodic local-density approximation density functional theory. Four stable polymorphous cells have been found including P212121, P21/c, P1̄ and Pbca, assigned to the orthorhombic, monoclinic and triclinic lattice systems. In addition, properties such as density, enthalpy of formation and detonation performance have also been predicted. As a result, the detonation velocity and pressure of two compounds are found to be very remarkable (DNAT: D = 9.17 km s(-1), P = 39.23 GPa; DNABT: D = 9.53 km s(-1), P = 40.92 GPa). Considering the tetrazole rings with energetic groups and the insensitive fragment of FOX-7, high positive heat of formation (583.50 kJ mol(-1) and 1081.39 kJ mol(-1)) and eminent performance render DNAT and DNABT to be very promising powerful energetically insensitive compounds. This work provides theoretical support for further experimental synthesis.

In the field of flexible metamaterial design, harnessing zero modes plays a key part in enabling reconfigurable elastic properties of the metamaterial with unconventional characteristics. However, only quantitative enhancement of certain properties succeeds in most cases rather than qualitative transformation of the metamaterials’ states or/and functionalities, due to the lack of systematic designs on the corresponding zero modes. Here, we propose a 3D metamaterial with engineered zero modes, and experimentally demonstrate its transformable static and dynamic properties. All seven types of extremal metamaterials ranging from null-mode (solid state) to hexa-mode (near-gaseous state) are reported to be reversibly transformed from one state to another, which is verified by the 3D-printed Thermoplastic Polyurethanes prototypes. Tunable wave manipulations are further investigated in 1D-, 2D- and 3D-systems. Our work sheds lights on the design of flexible mechanical metamaterials, which can be potentially extended from the mechanical to the electro-magnetite, the thermal or other types.

Energetic ionic salts based on ATO exhibit a good balance between low sensitivity and high detonation performance.

Bimetallic ammine borohydrides have been demonstrated to be capable of improving the efficiency of dehydrogenation and purity of the released hydrogen as compared to monometallic AMBs. We have obtained the optimized structures, orbital, and decomposition thermodynamic properties of several metal ammine borohydrides (AMB) containing [Li(BH4) n ]1–n groups by performing a solid-state density functional theory calculation. The structures are abbreviated as M–Li(BH4) x (NH3) y , where M means Li, Mg, Al, and Ca, respectively. [LiBH4] segments in these compounds play a crucial role in suppressing borane emission. Additionally, it activates the B–H···H–N bonds and decreases the hydrogen removal energies. Furthermore, the strength of M–N bonds will dictate the impurity of the ammine from the decomposition. The stability of the AMBs can be found as follows from the results of orbitals: LiMg(BH4)3(NH3)2 > Li2Al(BH4)5(NH3)4 > LiCa(BH4)3(NH3)2 > [Li(BH4)(NH3)]2. Finally, the [LiBH4] group can polarize the molecule and improve the efficiency of dehydrogenation process and purity of released hydrogen from bimetallic ammine borohydrides (AMBs) as compared to monometallic AMBs, which is due to the different bond strengths of M–B and M–N bonds (M denotes different metal cations here).

Two novel energetic nitrogen‐rich compounds 1,4‐diaminotetrazol‐5‐one (DATO) and 1,4‐dinitrotetrazol‐5‐one (DNTO) were proposed first and studied by quantum chemistry method with B3LYP/6‐31G* level of theory. The optimized geometry, IR predicted spectrum and thermochemical parameters, frontier molecular orbitals and molecular electrostatic potential were calculated for inspecting the electronic structure, molecular stability and chemical reactivity. The important macroscopic properties including density, enthalpy of formation, detonation parameters and impact sensitivity have been predicted as well. As a result, two designed compounds DATO and DNTO possess positive enthalpy of formation (395.79 and 342.77 kJ/mol), impressive detonation parameters (D = 8.80 km/s, P = 33.69 GPa; D = 8.89 km/s, P = 34.98 GPa) superior to the remarkable explosive RDX, acceptable sensitivities and might be promising candidates of energetic materials. Copyright © 2015 John Wiley & Sons, Ltd.