The AgI -promoted reaction of thiolactams with N-Boc amino acids yields an N-(α-aminoacyl) lactam that can rearrange through an acyl transfer process. Boc-deprotection results in convergence to the ring-expanded adduct, thereby facilitating an overall insertion of an amino acid into the thioamide bond to generate medium-sized heterocycles. Application to the site-specific insertion of amino acids into cyclic peptides is demonstrated.

The mechanism of the recently described N→C direction peptide synthesis through silver-promoted coupling of N-protected amino acids with thioacetylated amino esters was explored by using density functional theory. Calculation of the potential energy surfaces for various pathways revealed that the reaction proceeds through silver-assisted addition of the carboxylate to the thioamide, which is followed by deprotonation and silver-mediated extrusion of sulfur as Ag2 S. The resulting isoimide is the key intermediate, which subsequently rearranges to an imide through a concerted pericyclic [1,3]-acyl shift (O-sp(2) N 1,3-acyl migration). The proposed mechanism clearly emphasises the requirement of two equivalents of Ag(I) and basic reaction conditions, which is in full agreement with the experimental findings. Alternative rearrangement pathways involving only one equivalent of Ag(I) or through O-sp(3) N 1,3-acyl migration can be excluded. The computations further revealed that peptide couplings involving thioformamides require significant conformational changes in the intermediate isoformimide, which slow down the rearrangement process.

The Ag-I-promoted coupling reaction of thioamides and carboxylic acids is shown to be a useful method for the generation of unsymmetrical imides. The reaction proceeds efficiently with unhindered and electron-rich or neutral coupling partners, but not with hindered thioamides (such as thiopivalamides) or electron deficient thioamides (such as trifluorothioacetamides). Intriguingly, thioformamides are also ineffective coupling partners, despite having minimal steric or electronic influence. Hindered carboxylic acid coupling partners (such as pivalic acid) are tolerated, but electron deficient acids, such as trifluoroacetic acid, are ineffective coupling partners. Furthermore, an interplay of both steric and electronic effects is observed in the subsequent hydrolysis of unsymmetrical imides. Imides with a dimethoxybenzoyl group give high regioselectivity upon hydrolysis, favouring cleavage of the distal acyl group. Imides with a p-nitrobenzoyl or pivaloyl group give reversed selectivity, favouring cleavage of the proximal acyl group.

Periodic DFT method has been firstly used to calculate the bulk structure, electronic structure, electrical transferring and thermodynamic properties of crystalline 5-azido-1H-tetrazole (HCN7) and its four different salts. The anion CN7 − was included in all of the salts such as ammonium 5-azidotetrazolate ([NH4]+[CN7]−), hydrazinium 5-azidotetrazolate ([N2H5]+[CN7]−), guanidinium 5-azidotetrazolate ([CH6N3]+[CN7]− · H2O) and 1-aminoguanidinium 5- azidotetrazolate ([CH7N4]+[CN7]−). The simulation is in reasonable agreement with the experimental results. It is found the salts of HCN7 are more stable than itself because the band gap of the salts is larger. The density of state shows the p states of them (including HCN7 and its four salts) have played a very significant role in the reaction.

The geometric conformation and electronic structure of bis-(5-nitro-2H-tetrazolato-N2)tetraammine cobalt(III) perchlorate and its Ni/Fe/Cu/Zn analogues are studied under the TPSS (Tao-Perdew-Staroverov-Scuseria) levels of density functional theory in order to throw light on the relationship between their energy gaps and impact sensitivity. While the perchlorate ions are coordinated with the copper cation, which is different from the other four compounds. NBO (Natural bond orbital) analyses indicated that the metal-ligand interaction in the Co complex is covalent, while the others are ionic. The analysis of the electrostatic potential demonstrated that the O atoms from the nitro-tetrazole ring and perchlorate were primarily negative, while the other atoms were positive. The study was also conducted to gain a better understanding of the correlation of the energy gap and impact sensitivity.

The density functional theory(DFT) was used to study molecule and crystal of bis-(5-nitro-tetrazolato) tetraammine cobalt (III) perchlorate (BNCP). DFT calculations of BNCP were performed using four different spin-restricted functionals (SVWN5, PBE, TPSS and B3LYP) with the 6-31G** as the basis set. The results show that the TPSS (Tao, Perdew, Staroverov and Scuseria) functional best reproduce the experimental geometries. At the same time, the crystalline of BNCP was studied by PW91 of DMOL3. Then, the electronic structure of molecule and density of state, lattice energy, thermodynamic parameters of BNCP crystal were explored. The results show that the metal-ligand interaction in the title complex is covalent. And the frontier band consisted in the main of perchlorate ion, so it is the most active part of the compound. Meanwhile, the relationship between the temperature and thermodynamic parameters was obtained.

Density functional method was applied to study 1,5-diamino-1,2,3,4-tetrazole (DAT, CH4N6) in both gaseous and bulk states. The banding and electronic structures of crystalline have been investigated at DFT-B3LYP/6-311G** level of theory. Relaxed crystal structure compares well with experimental data. The light fluctuation of the frontier orbital, which is mainly formed by atomic orbital of N(4) (heterocycle), is the most reactive part of the molecule, which is in good agreement with the experimental results. The energy gap is 9.035 eV, which indicates that DAT is an insulator. The distribution of electrostatic potential is uniform, indicating DAT is insensitive. The charge density of the intermolecular regions in the plane is not overlaid, indicating that the intermolecular interaction between the neighboring molecules along this direction in the bulk is very weak. The overlap populations of N(1)-N(2) bonds are much less than those of other bonds, therefore the N(1)-N(2) bonds first rupture by external stimuli.

First-principles methods using the TPSS density functional level of theory with the basis set 6-31G** were applied to study (5-cyanotetrazolato-N(2)) pentaammine cobalt (III) perchlorate (CP) and Ni, Fe and Zn analogues in the gas phase. The optimized lowest-energy geometry of CP was calculated from reported experimental structural data using the TPSS method. The calculated values are in good agreement with those measured by X-ray diffraction. Ni, Fe and Zn analogues were constructed and calculated on the same basis. NBO results showed that the metal-ligand interactions have covalent character. Donor-acceptor analyses predicted that the delocalization energy E(2) decreases from Co to Zn, so the covalent nature of the complexes increases in the order Co>Fe>Ni>Zn. In addition, HOMO-LUMO composition was investigated to determine the stability of the title compounds.

An environmentally friendly energetic coordination compound [Zn(DAT)(6)](ClO4)(2) (DAT=1,5-diaminotetrazole) has been synthesized by using DAT as ligand, characterized by elemental analysis and FT-IR spectroscopy. The single crystal structure of the title compound was determined by applying X-ray single crystal diffraction, which shows that the crystal belongs to trigonal crystal system with space group P (3) over bar, and its crystal parameters: a=b=1.18398(9) nm, c=0.65700(10) nm, gamma= 120 degrees, V=0.79760(15) nm(3), and Z=1. There are one Zn2+, six DAT molecules and two ClO4- in the minimum asymmetric unit of the title compound. The central zinc(II) cation is coordinated by six N atoms from six DAT molecules to form a six-coordinated and distorted octahedral structure. Thermal decomposition mechanism of [Zn(DAT)(6)](ClO4)(2) was predicted based on DSC, TG-DTG and FT-IR analysis results. Also the kinetic parameters of the first exothermic process and sensitivities of the title compound have been studied. The result shows that the title compound has good friction sensitivity.

The molecular geometries, electronic structures, infrared spectra and thermochemical properties of cobalt and nickel tris(carbohydrazide) nitrates ([Co(CHZ)(3)](NO3)(2) and [Ni(CHZ)(3)](NO3)(2)) as well as copper bis(carbohydrazide) nitrate ([Cu(CHZ)(2)(NO3)(2)]) were investigated by using the density functional theory. The obtained results show that these three complexes have a six-coordinated octahedron feature, and the nitrate ions are also coordinated with the copper cation. Detailed natural bond orbital (NBO) analyses indicate that the donor-acceptor interactions between the ligands and metal cations result in decreasing of occupancies of amino N-H bond orbitals, and subsequently, cause the stretching vibrations of amino groups to shift to lower wave number, which is in accord with the experimental result. The NBO analyses also show that all of the metal cations are almost in +1 oxidation state, and the M-N coordination bonds are covalent, but the Cu-O coordination bonds are predominantly ionic in nature. The calculated heats of reaction reveal that the synthesis reactions for the studied compounds are exothermic. Moreover, the computed heats of formation predict that the stabilities of the title compounds decrease in the order: [Ni(CHZ)(3)](NO3)(2)> [Co(CHZ)(3)](NO3)(2)>[Cu(CHZ)(2)(NO3)(2)], which is in good agreement with the available experimental thermal stabilities.