Strongly positive electrostatic potential in the central areas of molecules of the energetic materials is one of the most important factors that determine the sensitivity of these molecules towards detonation....

Non-covalent selenium-selenium interactions between selenium-containing organic molecules were studied in crystal structures from the Cambridge Structural Database and by high-level quantum chemical calculations. Se…Se contacts in crystal structures were analyzed...

The existence of areas of strongly positive electrostatic potential in the central regions of the molecular surface of high-energy molecules is a strong indicator that these compounds are very sensitive towards detonation. Development of high-energy compounds with reduced sensitivity towards detonation and high efficiency is hard to achieve since the energetic molecules with high performance are usually very sensitive. Here we used Density Functional Theory (DFT) calculations to study a series of bis(acetylacetonato) and nitro-bis(acetylacetonato) complexes and to elucidate their potential application as energy compounds with moderate sensitivities. We calculated electrostatic potential maps for these molecules and analyzed values of positive potential in the central portions of molecular surfaces in the context of their sensitivity towards detonation. Results of the analysis of the electrostatic potential demonstrated that nitro-bis(acetylacetonato) complexes of Cu and Zn have similar values of electrostatic potential in the central regions (25.25 and 25.06 kcal/mol, respectively) as conventional explosives like TNT (23.76 kcal/mol). Results of analysis of electrostatic potentials and bond dissociation energies for the C-NO2 bond indicate that nitro-bis(acetylacetonato) complexes could be used as potential energetic compounds with satisfactory sensitivity and performance.

The computational design of explosives is becoming very popular since it represents a safe and environmentally friendly way of predicting the properties of these molecules. It is known that positive values of electrostatic potential in the central areas of the molecular surface are a good indicator of the sensitivity of high-energy materials towards detonation. The molecular electrostatic potential is routinely calculated for molecules of explosives using both geometries extracted from crystal structures, and computationally optimized geometries. Here we calculated and compared values of positive electrostatic potential in the centers of five classical high-energy molecules for geometries extracted from different crystal structures and theoretically optimized geometries. Density functional theory calculations performed at M06/cc-PVDZ level showed that there are significant differences in the values of electrostatic potentials in critical points obtained for different geometries of the same high-energy molecules. The study also showed that there was an excellent agreement in the values of electrostatic potentials calculated for optimized geometry of 1,3,5-trinitrobenzene and geometry of this molecule obtained by neutron diffraction experiments. The results of this study could help researchers in the area of the computational development of high-energy molecules to better design their studies and to avoid the production of erroneous results.

Hydrogen bonds are of greate importance for understanding of different processes in chemistry, crystalography and biology. [1] Properties of hydrogen bonds were subject of numerous experimental and theoretical studies. [1] Specially interesting case represent hydrogen bonds involving transition metal complexes since coordination of ligands can have significant influence on electrostatic potentials of coordinated molecules.[2] Here we present detailed analysis of crystalographic data combined with quantum chemical calculations of very strong hydrogen bonds between water and acetylacetonate ligand of different transition metal complexes.Cambridge Structural Database (CSD) was searched for all structures containing O-H/O interactions between water molecule and acetylacetonato ligands of transition metal complexes. Geometrical parameters extracted from crystall structures were analyzed and compared with quantum chemical calculations performed on model systems. The O-H/O interactions were studied on model systems containing water and neutral or charged square-planar complexes of Ir, Rh, Pd, and Pt. The strongest interactions were found in charged model systems and these results are in agreement with the predominant electrostatic nature of hydrogen bond (-16.54 kcal/mol). However, suprisingly strong O-H/O interactions were identified also in neutral model systems. The calculated energies of these interactions are -7.98 and -8.22 kcal/mol in [M(acac)(en)]/H2O (M = Ir(I), Rh(I)) model system, respectively.Using geometrical cristeria for hydrogen bonds 82 structures with 220 O-H/O contacts involving water molecule and coordinated acetylacetonato fragment were found. All extracted structures were statistically analyzed and results of analysis were in agreement with the results of quantum chemical calculations on model systems.Although the metal is not directly involved in hydrogen bonding, the results of theoretical studies show that the nature of metal atom has significant influence on the strength of hydrogen bonds of ligands.