A theoretical study of the complexes formed by hypohalous acids (HOX, X = F, Cl, Br, I, and At) with three nitrogenated bases (NH3, N2, and NCH) has been carried out by means of ab initio methods, up to MP2/aug-cc-pVTZ computational method. In general, two minima complexes are found, one with an OH···N hydrogen bond and the other one with a X···N halogen bond. While the first one is more stable for the smallest halogen derivatives, the two complexes present similar stabilities for the iodine case and the halogen-bonded structure is the most stable one for the hypoastatous acid complexes.

Competition of Hydrogen Bonds and Halogen Bonds in Complexes of Hypohalous Acids with Nitrogenated Bases

A novel halogen-free fire resistant epoxy resin with pendent spiro-cyclotriphosphazene groups was designed and synthesized via a three-step synthetic pathway. The chemical structures and compositions of spiro-cyclotriphosphazene precursors and final product were confirmed by 1H, 13C, and 31P NMR spectroscopy, mass spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. The thermal curing behaviors of the synthesized epoxy resin with 4,4′-diamino-diphenylmethane, 4,4′-diamino-diphenyl sulfone, and novolac as hardeners were investigated by differential scanning calorimetry (DSC), and the curing kinetics were also studied under a nonisothermal condition. The evaluation of the thermal properties demonstrated that these thermosets achieved a good thermal resistance due to their high glass transition temperatures more than 150 °C, and also gained high thermal stabilities with high char yields. The flammability characteristics of the spirocyclic phosphazene-based epoxy thermosets cured wit...

Novel Spirocyclic Phosphazene-Based Epoxy Resin for Halogen-Free Fire Resistance: Synthesis, Curing Behaviors, and Flammability Characteristics

As-grown transition metal dichalcogenides are usually chalcogen deficient and contain a high density of chalcogen vacancies, which are harmful to the electronic properties of these materials. Based on the first-principles calculation, in this study the repairing of the S vacancy in the MoS2 monolayer has been investigated by using CO, NO and NO2 molecules. For CO and NO, the repairing process consists of the first molecule filling the S vacancy and the removing of the extra O atom by the second molecule. However, for NO2, when the molecule fills the S vacancy, it is dissociated directly to form an O-doped MoS2 monolayer. After the repair, the C, N and O-doped MoS2 monolayers can be obtained by the adsorption of CO, NO, and NO2 molecules, respectively. And in particular, the electronic properties of these materials can be significantly improved by N and O doping. Furthermore, according to the calculated energy, the process of S vacancy repairing with CO, NO and NO2 should be easily achieved at room temperature. This study presents a promising strategy for repairing MoS2 nanosheets and improving their electronic properties, which may also apply to other transition metal dichalcogenides.

Repairing sulfur vacancies in the MoS2 monolayer by using CO, NO and NO2 molecules

Investigation of heavy metal atoms adsorption onto graphene and graphdiyne surface: A density functional theory study

Fine structural tuning of diketopyrrolopyrrole-cored donor materials for small molecule-fullerene organic solar cells: A theoretical study

The tautomerization pathways and kinetics of 1,5-diaminotetrazole (DAT) have been investigated by means of second-order Moller-Plesset perturbation theory (MP2) and coupled-cluster theory, with single and double excitations including perturbative corrections for triple excitations (CCSD(T)). Five possible tautomers, namely 4-hydro-1-amino-5-imino-tetrazole (a), 2,5-diamino-tetrazole (b), 1,5-diamino-tetrazole (c), 2-hydro-1-imino-5-amino-tetrazole (d), and 2,4-dihydro-1,5-diimino-tetrazole (e) were identified. The structures of the reactants, transition states, and products along with the tautomerism pathways were optimized by the MP2 method using the 6-311G** basis set, and the energies were refined using CCSD(T)/6-311G**. The minimum-energy path (MEP) information for DAT was obtained at the CCSD(T)/6-311G**//MP2/6-311G** level of theory. Therein, reaction 2 (c → b) is an amino-shift reaction, while reaction 1 (c → a), reaction 3 (c → d), reaction 4 (a → e), and reaction 5 (d → e) are reactions of hydrogen-shift tautomerization. The calculated results show that 2,5-diaminotetrazole (b) with the minimum energy (taking c as a standard) among five tautomers, is the energetically preferred tautomer of DAT in the gas phase. In addition, the energy barrier of reaction 2 is 71.65 kcal · mol−1 in the gas phase, while reaction 1 takes place more easily with an activation barrier of 61.53 kcal · mol−1 also as compared to 63.71 kcal · mol−1 in reaction 3. Moreover, the tautomerization of reaction 4 requires the largest energy barrier of 83.29 kcal · mol−1, which is obviously bigger than reaction 5 with a value of 73.78 kcal · mol−1. Thus, the hydrogen-shift of c to a is the easiest transformation, while the tautomerization of a to e is the hardest one. Again, the rate constants of tautomerization have been obtained by TST, TST/Eckart, CVT, CVT/SCT, and CVT/ZCT methods in the range 200-2500 K, and analysis indicated that variational effects are small over the whole temperature range, while tunneling effects are significant in the lower temperature range.

Theoretical study on the tautomerization of 1,5-diaminotetrazole (DAT).

The pathway and ab initio direct kinetics of the decomposition 5-aminotetrazole (5-ATZ) to HN3 and NH2CN was investigated. Reactant, products and transition state were optimized with MP2 and B3LYP methods using 6–311G** and aug-cc-pVDZ basis sets. The intrinsic reaction coordinate curve of the reaction was calculated using the MP2 method with 6–311G** basis set. The energies were refined using CCSD(T)/6–311G**. Rate constants were evaluated by conventional transition-state theory (CVT) and canonical variational transition-state theory (TST), with tunneling effect over 300 to 2,500 K. The results indicated that the tunneling effect and the variational effect are small for the calculated rate constants. The fitted three-parameter expression calculated using the CVT and TST methods are $${\text{k}}\left( {\text{T}} \right) = 4.07 \times 10^{11} \times {\text{T}}^{0.84} \times {\text{e}}^{\left( {{{ - 2.42 \times 10^4 } \mathord{\left/ {\vphantom {{ - 2.42 \times 10^4 } {\text{T}}}} \right. \kern-\nulldelimiterspace} {\text{T}}}} \right)} {\text{s}}^{ - 1} $$
 and $${\text{k}}\left( {\text{T}} \right) = 2.09 \times 10^{11} \times {\text{T}}^{0.89} \times {\text{e}}^{\left( {{{ - 2.36 \times 10^4 } \mathord{\left/ {\vphantom {{ - 2.36 \times 10^4 } T}} \right. \kern-\nulldelimiterspace} T}} \right)} {\text{s}}^{ - 1} $$
 , respectively.

The mechanism and kinetics of decomposition of 5-aminotetrazole.

The tautomerism and intramolecular hydrogen shifts of 5-amino-tetrazole in the gas phase were studied in the present work. The minimum energy path (MEP) information of 5-amino-tetrazole was obtained at the CCSD(T)/6–311G**//MP2/6–311G** level of theory. The six possible tautomers of 1H, 4H-5-imino-tetrazole (a), 1H-5-amino-tetrazole (b), 2H-5-amino-tetrazole (c), 1H, 2H-5-imino-tetrazole (d), the mesoionic form (e) and 2H, 4H-5-imino-tetrazole (f) were investigated. Among these tautomers, there are 2 amino- forms, 3 imino- forms, and 1 mesoionic structure form. In all the tautomers, 2-H form (c) is the energetically preferred one in the gas phase. In the imino- tautomers, the energy value of the compound d is similar as that of the compound f but it is higher than the energy value of the compound a. The potential energetic surface (PES) and kinetics for five reactions have been investigated. Reaction 2 (b→c) was hydrogen shifts only in which the 1-H and 2-H rearrangement. This means that the reaction 2 (b→c) is energetically favorable having an activation barrier of 45.66 kcal·mol−1 and the reaction energies (ΔE) is only 2.67 kcal·mol−1. However, the reaction energy barrier for tautomerism of reaction 1 (b→e) is 54.90 kcal·mol−1. Reaction 1 (b→a), reaction 3 (c→d), and reaction 5 (c→f) were amino- →imino- tautomerism reactions. The energy barriers of amino- →imino- tautomerism reactions required are 59.39, 65.57, 73.61 kcal·mol−1 respectively in the gas phase. The calculated values of rate constants using TST, TST/Eckart, CVT, CVT/SCT and CVT/ZCT methods using the optimized geometries obtained at the MP2/6–311G** level of theory show the variational effects are small over the whole temperature range, while tunneling effects are big in the lower temperature range for all tautomerism reactions.

Theoretical studies on the tautomerism and intramolecular hydrogen shifts of 5-Amino-tetrazole in the gas phase

In this paper, the synthesis principles and methods of 1,1-spiro(ethylenediamino)-3,3,5,5-tetrachlorocyclotriphosphazene (ETCCTP) and its nitration product of 1,1-spiro(N,N′-dinitroethylenediamino)-3,3,5,5-tetrachlorocyclotriphosphazene (DNETCCTP) have been reported. Their structures were demonstrated by elemental analysis, NMR, MS, and FTIR methods. Besides, the crystal of the title compound was obtained and characterized by X-ray single-crystal diffraction technique. The obtained results showed that the crystal belongs to Crystal system of Monoclinic with space group of C2/c. Based on the crystal data, geometries and normal vibrations have been obtained by using the B3LYP method with the 6-31G**, 6-311G**, and 6-31++G** basis sets. The calculation results further demonstrate the molecular structure of the title compound.

High energy density compounds from cyclophosphazene. II. The preparation, structural characterization, and theoretical studies of 1,1-spiro(ethylenediamino)-3,3,5,5-tetrachlorocyclotriphosphazene and its nitration product

Theoretical study for high-energy-density compounds from cyclophosphazene III. A quantum chemistry study: High nitrogen-contented energetic compound of 1,1,3,3,5,5,7,7-octaazido-cyclo-tetraphosphazene: N4P4(N3)8

Li-Na Feng

Papers

Theoretical study on the tautomerization of 1,5-diaminotetrazole (DAT).

The mechanism and kinetics of decomposition of 5-aminotetrazole.

Theoretical studies on the tautomerism and intramolecular hydrogen shifts of 5-Amino-tetrazole in the gas phase

High energy density compounds from cyclophosphazene. II. The preparation, structural characterization, and theoretical studies of 1,1-spiro(ethylenediamino)-3,3,5,5-tetrachlorocyclotriphosphazene and its nitration product

Theoretical study for high-energy-density compounds from cyclophosphazene III. A quantum chemistry study: High nitrogen-contented energetic compound of 1,1,3,3,5,5,7,7-octaazido-cyclo-tetraphosphazene: N4P4(N3)8