Theoretical study of the influence of halogen substituents on sensitivity of polycyclic nitroaromatic explosives

Positive values of electrostatic potential on the surface of high-energy molecules are a good indicator of the high sensitivity towards detonation. Here we used Bond Dissociation Energy and Molecular Electrostatic Potential calculations to predict the influence of the halogen substituents on the detonation properties of selected halogen-containing dinitronaphthalenes. Results of ab initio calculations indicated that halogen substituents may affect the geometry of the nitro- groups and lead to decreased stability of the weakest C-N bonds. Presence of halogen substituents also affects the values of the electrostatic potentials in the central regions of the molecular surfaces

Supplementary data for the article: Veljković, D. Ž. Strong C–H/O Interactions between Polycyclic Aromatic Hydrocarbons and Water: Influence of Aromatic System Size. Journal of Molecular Graphics and Modelling 2018, 80, 121–125. https://doi.org/10.1016/j.jmgm.2017.12.014

Supplementary material for: [https://doi.org/10.1016/j.jmgm.2017.12.014]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2112]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/2815

JIMP 2 Software as a teaching tool: Understanding orbitals using fenskee-hall method

Teaching molecular orbital concept to undergraduate students is known to be very challenging; analysis of examination data for undergraduate students reveals that they do not have a clear understanding of the concepts of atomic and molecular orbitals (Tsaparlis, 1997). Understanding of the orbital concept has been subject to considerable debate and research (Barradas-Solas and Sánchez Gómez, 2014). One of teaching strategies to deal with this problem is based on usage of different quantum chemical software to calculate shape, energy and to visualize molecular orbitals. The main downside of this approach is the fact that quantum chemical calculations are often very time-consuming, especially in the case of molecules that contain transition metal atoms. Fenske-Hall method is ab initio method mainly developed for molecular orbitals calculation of transition metal complexes and organometallic compounds (Hall and Fenske, 1972). It was shown that this method is very fast, and very accurate (results are similar to the results obtained by more rigorous and more time-consuming DFT methods). Here we present a series of computational laboratory exercises using Fenske-Hall method incorporated in Jimp2 software to calculate and visualize both atomic and molecular orbitals. Students will learn how to calculate energy and visualize molecular orbitals of simple molecules. Exercises provide deeper insight into relationship between atomic and molecular orbitals with special emphasis on calculation of contribution of atomic orbitals in particular molecular orbital. Using results of Fenske-Hall calculations, students will construct molecular-orbital diagrams for simple molecules

Tris(3-nitropentane-2,4-dionato-κ2 O,O′) Complexes as a New Type of Highly Energetic Materials: Theoretical and Experimental Considerations

Decreasing the sensitivity towards detonation of high-energy materials (HEMs) is the ultimate goal of numerous theoretical and experimental studies. It is known that positive electrostatic potential above the central areas of the molecular surface is related to high sensitivity towards the detonation of high-energy molecules. Coordination compounds offer additional structural features that can be used for the adjustment of the electrostatic potential values and sensitivity towards detonation of this class of HEM compounds. By a careful combination of the transition metal atoms and ligands, it is possible to achieve a fine-tuning of the values of the electrostatic potential on the surface of the chelate complexes. Here we combined Density Functional Theory calculations with experimental data to evaluate the high-energy properties of tris(3-nitropentane-2,4-dionato-κ2 O,O′) (nitro-tris(acetylacetonato)) complexes of Cr(III), Mn(III), Fe(III), and Co(III). Analysis of the Bond Dissociation Energies (BDE) of the C-NO2 bonds and Molecular Electrostatic Potentials (MEP) showed that these compounds may act as HEM molecules. Analysis of IR spectra and initiation of the Co(AcAc-NO2)3 complex in the open flame confirmed that these compounds act as high-energy molecules. The measured heat of combustion for the Co(AcAc-NO2)3 complex was 14,133 J/g, which confirms the high-energy properties of this compound. The results also indicated that the addition of chelate rings may be used as a new tool for controlling the sensitivity towards the detonation of high-energy coordination compounds

Supplementary data for article: Malenov, D. P.; Janjić, G. V.; Veljković, D. Ž.; Zarić, S. Mutual Influence of Parallel, CH/O, OH/Pi and Lone Pair/Pi Interactions in Water/Benzene/Water System. Computational and Theoretical Chemistry 2013, 1018, 59–65. https://doi.org/10.1016/j.comptc.2013.05.030

Supplementary material for: [https://doi.org/10.1016/j.comptc.2013.05.030]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1390

Theoretical Study of σ-hole Bonding between Selenium Atoms in Crystal Structures of Organoselenium Compounds

Non-covalent interactions involving selenium atoms are of great importance in chemistry and biochemistry due to the prominent role of selenium-containing molecules (like Se-antioxidants and selenoenzymes) in different biochemical processes. In this work, we combined analysis of crystallographic data extracted from crystal structures of selenium-containing molecules with the quantum chemical calculations to reveal the energy and geometry of seleniumselenium interactions in crystal structures of organoselenium compounds. In addition, Energy Decomposition Analysis was performed on model systems to reveal the nature of selenium-selenium interactions. Results of analysis of crystal structures were in excelent agreement with the results of quantum chemical calculations performed on model systems. Results of Energy Decomposition Analysis calculations showed that although the dispersion is the most important component of energy of selenium-selenium interactions, electrostatic component is also very strong. Results also suggest that electrostatic component has crucial role in defining the geometry of selenium-selenium interactions. Reduced Density Gradient calculations on model systems showed that selenium-selenium interactions are often accompanied with additional C-H ...Se interactions.4th International Symposium on Halogen Bonding (ISXB-4 Virtual) held as a virtual event from 2 – 5 November 202

Quantum Chemical Study of Influence of Halogen Bonds on the Sensitivity of Organic Explosives

Predicting the properties of new energetic materials using computer simulations is the ultimate goal of many theoretical studies. [1] One of the most important tools for revealing the sensitivity of the energetic molecules is Molecular Electrostatic Potential (MEP). It is known that molecules of classical C,H,N,O-explosives have strongly positive electrostatic potential above the central areas of the molecular surfaces. [2] Values of electrostatic potentials on the surface of energetic molecules could be adjusted by introducing electron-donating groups in the molecules but also by non-covalent bonding. [2] While it is known that hydrogen bonds do affect the electrostatic potential and sensitivity of the energetic molecules, [3] influence of halogen bonds in halogen-containing energetic molecules is yet to be revealed. In this work, Cambridge Structural Database (CSD) was searched for the crystal structures of halogen-containing molecules of explosives. Halogen bonding patterns were analyzed in extracted crystal structures. Based on the analysis of crystal structures, model systems for quantum chemical calculations were made. Quantum chemical calculations were used to calculate electrostatic potential maps of selected molecules and to examine the influence of halogen bonding on the electrostatic potential in the central areas of the studied energetic molecules. Results of this study could be of great importance for the development of the new rules for the design of halogen-containing energetic materials with improved sensitivity toward detonation

Struktura izvoza i uvoza mleka i mlečnih proizvoda iz Srbije

The structure of the milk supply market depends on processing capacities in Serbia, which are more oriented to the production of dairy products pasteurized and sterilized milk and fermented dairy products (yoghurt, cream, sour milk, etc.), while the production of solid dairy products (cheeses, cream, spreads, butter, powdered milk, etc.) is significantly lower. Taking into consideration the current situation in Serbia regarding the primary production, purchase and processing of milk, an overview is given of the foreign trade balance of milk and dairy products and their participation in exports and imports. The analysis of the foreign trade of milk and dairy products for the period 2007- 2017 highlights products that are exported and have stable export tendencies, as well as scarce products which are imported and have a markedly negative balance sheet in the observed period. We also analyzed major export-import destinations of Serbia for the trade exchange of milk and dairy products, which primarily refers to the CEFTA countries, the European Union and the Russian Federation.Struktura tržišne ponude mleka zavisi od preradnih kapaciteta u Srbiji, koji su više orijentisani na proizvodnju mlečnih proizvoda pasterizovanog i sterilizovanog mleka i fermentisanih mlečnih proizvoda (jogurt, pavlaka, kiselo mleko itd.) dok je proizvodnja čvrstih mlečnih proizvoda (sirevi, pavlake, namazi, maslac, mleko u prahu itd.) značajno manja. Uzimajući u obzir aktuelno stanje u Srbiji u primarnoj proizvodnji, otkupu i preradi mleka, dat je kratak osvrt na spoljnotrgovinski bilans mleka i mlečnih proizvoda i njihovo učešće u izvozu i uvozu. Analizom spoljnotrgovinske razmene mleka i proizvoda za posmatrani period 2007-2017. godine ukazano je na proizvode koji se izvoze i imaju stabilne izvozne tendencije, kao i na deficitarne proizvode koji se uvoze i imaju izražene negativne bilanse u posmatranom periodu. Analizirane su i najvažnije izvozno- uvozne destinacije sa kojima Srbija ostvaruje trgovinsku razmenu za mleko i mlečne proizvode, pri čemu se to prvenstveno odnosi na zemlje CEFTA grupe, Evropske unije i Rusku Federaciju

How aromatic system size affects the sensitivities of highly energetic molecules?

Positive values of electrostatic potentials above the central regions of the molecular surface are strongly related to the high sensitivities of highly energetic molecules. The influence of aromatic system size on the positive values of electrostatic potentials and bond dissociation energies of C–NO2 bonds was studied by Density Functional Theory (DFT) calculations on a series of polycyclic nitroaromatic molecules. Calculations performed at PBE/6-311G** level showed that with the increase of the aromatic system size, values of positive electrostatic potential above the central areas of selected energetic molecules decrease from 32.78 kcal mol−1 (1,2,4,5-tetranitrobenzene) to 15.28 kcal mol−1 (2,3,9,10-tetranitropentacene) leading to the decrease in the sensitivities of these molecules towards detonation. Results of the analysis of electrostatic potential maps were in agreement with the trends in bond dissociation energies calculated for C–NO2 bonds of studied nitroaromatic molecules. Bond dissociation energies values indicate that the C–NO2 bond in the molecule of 1,2,4,5-tetranitrobenzene (56.72 kcal mol−1) is weaker compared to the nitroaromatic molecules with the additional condensed aromatic rings and with a similar arrangement of –NO2 groups (59.75 kcal mol−1 in the case of 2,3,9,10-tetranitropentacene). The influence of the mutual arrangement of –NO2 groups on the sensitivity of nitroaromatic molecules was also analyzed. Results obtained within this study could be of great importance for the development of new classes of highly energetic molecules with lower sensitivity towards detonation.Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/4804

Modification of electrostatic potentials of organometallic compounds as a tool in a design of new class of high energetic materials

Design of new classes of high energetic materials (HEM) with lower sensitivity towards detonation is the ultimate goal of numerous experimental and theoretical studies.[1] One of the most important properties that define the impact sensitivity of HEM molecules is the value of molecular electrostatic potential (MEP) above the central regions of molecular surface. Positive values of MEP are strongly related to high sensitivity of HEM molecules towards detonation.[2] In our previous work, we showed that it is possible to modify MEP of chelate complexes by careful selection of ligands and metal atoms.[3] In this work, we calculated MEPs for series of metallocene molecules and analysed results in the context of their possible detonation properties. Calculations performed at B3LYP/def2TZVP level showed that negative values of MEP above the center of the cyclopentadienyl ligand of ferrocene (-16.55 kcal/mol) were changed to positive values (7.11 kcal/mol) upon the addition of NO2 substituent to cyclopentadienyl ligand. Results of DFT calculations also showed that changing of transition metal atom in metallocene molecule could be used for fine-tuning of electrostatic potential values above the central region of cyclopentadienyl ligands