Thermal decomposition of energetic materials. Part 9. Polymorphism, crystal structures, and thermal decomposition of polynitroazabicyclo[3.3.1]nonanes

Tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine thin films: deposition, characterization and application

Thin films of pure tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine (TIPCuPc) , a novel functionalized phthalocyanine, and its hybrid junctions with colloidal rod-like TiO2 nanocrystals (NCs) were deposited in order to elucidate their properties and application in piezoelectric chemical sensors. The strong tendency of the phthalocyanine to assembly was confirmed at the air/water interface by advanced Brewster Angle Microscopy (BAM) and UV-vis reflection spectroscopy techniques. In particular, H-type aggregates, in situ and at the air/water interface, self-associate in aligned 3D bulky domains. The characteristics of the molecule and of the assemblies were studied in the solid state by means of UV-vis spectroscopy, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and Atomic Force Microscopy (AFM). These studies prompted investigation of the operating conditions to process the bare TIPCuPc and related TiO2 NC-based hybrid junctions as sensing active layers for phenol pollutants integrated in a Quartz Crystal Microbalance (QCM). Interestingly, the preferentially oriented phthalocyanine LB-film undergoes chemical interactions with the NC film, which enhances the sensitivity of the QCM sensor.

Polymorph Farming of Acetaminophen and Sulfathiazole on a Chip

PURPOSE

The aim of this paper is to understand at a given temperature (1) the role of template films, the droplet volume of a saturated sulfathiazole aqueous solution and the solvent on polymorph screening of sulfathiazole on a silicon wafer, and (2) the effect of template films on the acetaminophen crystal face at the template-crystal interface.

MATERIALS AND METHODS

Template Effect: Spun cast template films of non-annealed chitosan and annealed chitosan at 140 degrees C on silicon wafers were prepared. A 0.01-cm(3) saturated sulfathiazole aqueous solution droplets were deposited on both kinds of chitosan film. Sulfathiazole crystals were produced on those films by evaporation at 25 degrees C. Volume Effect: Different droplet volumes of a saturated sulfathiazole aqueous solution ranging from 0.01 to 0.14 to 2.7 cm(3) were deposited on non-annealed chitosan films. Sulfathiazole crystals were generated on those films by evaporation at 25 degrees C. Solvent Effect: 0.01 cm(3) saturated sulfathiazole methanol solution droplets were deposited on non-annealed chitosan films and sulfathiazole crystals were formed on those films by evaporation at 25 degrees C. The formation pathways of different sulfathiazole crystal polymorphs of the above mentioned effects were analyzed and verified by systematic studies. Template-crystal Interfacial Study: Millimeter-sized acetaminophen crystals were successfully grown on non-annealed chlorosulfonated poly(ethylene) (PE-Chl) and chitosan template films by cooling the saturated acetaminophen aqueous solution from 50 to 25 degrees C in which those template films were immersed. The bonding energies for specific carbons collected by electron spectroscopy for chemical analysis (ESCA) at the acetaminophen crystal surface, together with the molecular interactions between acetaminophen and PE-Chl and between acetaminophen and chitosan in separately prepared solid dispersion film samples detected by Fourier transformed infrared (FTIR) spectroscopy, proved to be useful for identifying the crystal face of acetaminophen essential for its specific intermolecular interactions at the template-crystal interface.

RESULTS

Thermodynamically metastable sulfathiazole Form I crystals were reproducibly obtained on the non-annealed chitosan films whereas the stable sulfathiazole Form III crystals were repeatedly formed on the annealed chitosan films. Droplet volumes and solvents were also found responsible for the polymorphic outcome of sulfathiazole in the kinetically driven area of two overlapping metastable zones from two competing polymorphs of Form I and Form III. Thermodynamically stable sulfathiazole Form III crystals were formed on the non-annealed chitosan films instead when the droplet volumes of a saturated sulfathiazole aqueous solution were increased from 0.01 to 0.14 cm(3) and 2.7 cm(3). When the solvent was changed from water to methanol, the thermodynamically stable sulfathiazole Form III crystals were again observed on the non-annealed chitosan films even from the 0.01 cm(3) saturated sulfathiazole methanol solution droplets.

CONCLUSIONS

Template surfaces were thought to provide specific functional groups to either change the energy barrier for the nuclei formation of the thermodynamically metastable Form I or alter the droplet contact angle and the droplet surface area which was related to the droplet evaporation time. The evaporation time determines the amount of time available for the polymorphic transformation from Form I to Form III. Apparently, droplet volumes could also determine the amount of time needed to reach supersaturation and the amount of time available for a polymorphic transformation from Form I to Form III. In addition, the molecular conformation and viscosity of solvents such as methanol might alter the original nucleation kinetics in water and lead to a more rapid polymorphic transformation from Form I to Form III. Template films of PE-Chl and chitosan were found to be critical for determining the face of a millimeter-sized acetaminophen crystal at the template-crystal interface. The idea of performing polymorph screening on the template film deposited on a chip has opened up a new doorway to examine the roles of: (1) various kinds of drug carrier in the form of a template film, (2) the droplet volume of a saturated solution, and (3) the type of solvent used, in polymorphic control. Growing millimeter-sized crystals directly on the chip of template has also provided a convenient technology enabling platform for examining the crystal-template interface by solid-state characterization techniques such as ESCA.

Vibrational behavior of the -NO2 group in energetic compounds

The vibrational modes of the -NO2 group in more than fifty energetic compounds containing the C-nitro and N-nitro functionalities were observed and then calculated in optimized structures using density functional theory (B3LYP/6-31+G*). The trends in the symmetric and asymmetric stretches and scissor and out-of-plane deformations were explained by these calculations. A previously unreported correlation was found between the nitro group internal bonding angle and its asymmetric stretching frequency. The concept of meta and ortho/para directing groups was applicable to the trends in coupled motions in the nitroaromatic compounds. Both the scissor motion of C-NO2 groups and the out-of-plane deformation of N-NO2 groups were found to be virtually insensitive to the remainder of the molecule. These findings may be useful in analytical methods of explosive detection based on their infrared (IR) spectra.

Nitrolysis of a Highly Deactivated Amide by Protonitronium. Synthesis and Structure of HNFX(1)

Efficient N-nitrolysis of highly deactivated 3,3,7,7-tetrakis(difluoramino)octahydro-1,5-bis(4-nitrobenzenesulfonyl)-1,5-diazocine (1) has been achieved by the use of protonitronium reagent formed in the system nitric acid-trifluoromethanesulfonic acid, producing 3,3,7,7-tetrakis(difluoramino)octahydro-1,5-dinitro-1,5-diazocine (HNFX, 2) in 65% yield in a nonoptimized reaction. The crystal structure of the first morphology of HNFX contains cavities in the form of channels through its unit cell; the observed density is 1.807 g.cm(-)(3).