A new approach to study semi-coordination using two 2-methyl-5-nitroimidazole copper(ii) complexes of biological interest as a model system

Two novel copper(ii) complexes [Cu(2mni)2(H2O)2](NO3)2·2H2O (1) and [Cu(2mni)2(NO3)2] (2), where 2mni is 2-methyl-5-nitroimidazole, were prepared and characterized in the solid state using single-crystal and powder X-ray diffraction analyses, EPR, electronic and vibrational spectroscopies (FTIR and Raman), and thermogravimetric methods. Both products present an elongated distorted octahedral geometry with axial Cu-O bond lengths of 2.606(14) and 2.593(15) Å, indicating semi-coordination. Density functional theory (DFT) calculations at the B3LYP/LANL2DZ theory level were used to study the electronic properties of 1 and 2. The Independent Gradient Model (IGM) was employed to determine the Intrinsic Bond Strength Index (IBSI) of the semi-coordination and to plot δg isosurfaces for the electronic sharing between the metal center and ligands. A moderate to weak antibacterial activity against Escherichia coli cultures was found for 1 with a 50% growth inhibition (GI50) value of 0.25 mmol L-1. To the best of our knowledge, this is the first time that the semi-coordination analysis using IGM was carried out for a copper(ii) complex with axial elongation, finding a good correlation between the bond length and the IBSI, and the study was extended for a series of analogous complexes described in the literature.

Design and properties of a new family of bridged bis(nitraminotetrazoles) as promising energetic materials

A new family of bridged bis(nitraminotetrazoles) on the basis of the combination of bistetrazoles and the energetic nitramino as well as various linkage groups was designed, and their properties were investigated in detail. Their good performance makes them promising candidates for new environmentally friendly energetic materials.

2-Methyl-substituted monotetrazoles in copper(ii) perchlorate complexes: manipulating coordination chemistry and derived energetic properties

Several new energetic coordination compounds (ECC) have been prepared using two 2-methyl-substituted tetrazoles. By simply changing the reaction conditions, the coordination sphere of the metal center can be manipulated in order to obtain different complexes with varying energetic properties.

Metal nanofoams via a facile microwave-assisted solvothermal process

A novel, facile, non-hazardous, low temperature/pressure microwave solvothermal method of producing pure copper, silver, and nickel metal nanofoams is presented.

High pressure study of a highly energetic nitrogen-rich carbon nitride, cyanuric triazide

Cyanuric triazide (CTA), a nitrogen-rich energetic material, was compressed in a diamond anvil cell up to 63.2 GPa. Samples were characterized by x-ray diffraction, Raman, and infrared spectroscopy. A phase transition occurring between 29.8 and 30.7 GPa was found by all three techniques. The bulk modulus and its pressure derivative of the low pressure phase were determined by fitting the 300 K isothermal compression data to the Birch-Murnaghan equation of state. Due to the strong photosensitivity of CTA, synchrotron generated x-rays and visible laser radiation both lead to the progressive conversion of CTA into a two dimensional amorphous C=N network, starting from 9.2 GPa. As a result of the conversion, increasingly weak and broad x-ray diffraction lines were recorded from crystalline CTA as a function of pressure. Hence, a definite structure could not be obtained for the high pressure phase of CTA. Results from infrared spectroscopy carried out to 40.5 GPa suggest the high pressure formation of a lattice built of tri-tetrazole molecular units. The decompression study showed stability of the high pressure phase down to 13.9 GPa. Finally, two CTA samples, one loaded with neon and the other with nitrogen, used as pressure transmitting media, were laser-heated to approximately 1100 K and 1500 K while compressed at 37.7 GPa and 42.0 GPa, respectively. In both cases CTA decomposed resulting in amorphous compounds, as recovered at ambient conditions.

Comparison of GIAO and CSGT for calculating (13) C and (15) N nuclear magnetic resonance chemical shifts of substituent neutral 5-aminotetrazole and 5-nitrotetrazole compounds

The comparison of the gauge-including atomic orbital (GIAO) and the continuous set of gauge transformation methods for calculating nuclear magnetic chemical shifts (CSs) mainly at density functional levels of theory are presented. Isotropic (13)  C and (15)  N magnetic CS for 14 compounds of tetrazoles are reported. Compared with establishing a convenient and consistent protocol to be employed for confirming the experimental (13)  C and (15)  N NMR spectra of tetrazole compounds, different combinations of functionals and basis sets were considered. The most reliable results were obtained at GIAO/B3LYP/aug-cc-pVDZ with integral equation formulation for the polarizable continuum model (PCM), which has the smallest root mean square errors and can be used to calculate (13)  C and (15)  N NMR CS with a very high accuracy for tetrazoles. These results show that the accurately calculated (15) N NMR CS of tetrazoles could be used for the evaluation of the intrinsic relationship between structure and explosive properties.

Nitroimino-tetrazolates and oxy-nitroimino-tetrazolates

Highly energetic 1,1'-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) salts were obtained by reacting equimolar quantities of the acidic 1,1'-ethylenebis(oxy)bis(5-nitroimino-tetrazole) and energetic bases in aqueous solution. Additionally, metathesis of silver 1,1'-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) with diaminoguanidinium chloride or triaminoguanidinium chloride gave the corresponding oxy-nitroimino-tetrazolate salt. These salts were fully characterized using IR and multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC), and, in some cases, 2·2H(2)O, 8·2H(2)O, 10, 13·2H(2)O and 14, with single crystal X-ray structuring. The heats of formation for all compounds were calculated with Gaussian 03 and then combined with measured densities to determine detonation pressures (P) and velocities (D) of the energetic materials (Cheetah 5.0). The impact sensitivities of all salts were found to be less than those of the parent compounds. The physical and detonation properties of these oxy-nitroimino-tetrazolate salts are comparable to the analogous newly prepared diaminoguanidinium and triaminoguanidinium 1,1'-ethylenebis(5-nitroimino-tetrazolate)s.