Elaboration of a Predictive Qsar Model of the Anti-Paludial Activity of a Series of Dihydrothiophenone Molecules at Theory Level B3LYP/ 6-31G (d, p)

The purpose of this study is to develop a QSAR model predictive of the antimalarial activity of a series of Dihydrothiophenone molecules using quantum chemical methods. The molecules were optimized from the B3LYP/6-31G (d, p) level of theory. The extracted descriptors are the vibrational frequency of the carbonyl group (Ѵ(C=O)), enthalpy of formation (Δ f H°), the valence angle between the carbon-nitrogen-carbon atoms α(C-N-C) and the ionization potential (I); The application of the RLM method of the XLSTAT program allowed us to develop a regression model. The statistical indicators (R²=93.50%, S=0.211, F=43.678) of the developed model attest to its robustness and reliability. Internal and external validation parameters (Q2loo et Q2ext) reveal that the established model performs well in predicting the antimalarial activity of the series of molecules studied. It can therefore be used to design new HD molecules belonging to its field of applicability at a 95% confidence level.

PARAMETERIZATION OF REAXFF POTENTIAL OF MG/AL/SI/O INTERACTION AND INVESTIGATION OF MECHANICAL PROPERTIES FOR S-GLASS

New ReaxFF parameters are developed for the description of Mg/Al/Si/O interaction for the Magnesium Aluminosilicate (MAS) glass structure. The training set contains energy curves from equation of state for various Mg/Al/Si/O crystals, valence angle and bond distance scan, and heat of formation for the Mg/Al/Si/O interactions. A semi-automated Genetic Algorithm assisted by Artificial Neural Network is applied for this parametrization. Validation efforts showed the current ReaxFF parameter set can describe the atomistic structure and property of tectosilicate MAS glass including S-glass. Estimated quasi-static modulus of S-glass structure matches well with experimental value. Analysis shows the key of high modulus of S-glass is numerous Mg-BO (Bridge Oxygen) interactions across the Mg-O-AlSi structure. In addition, atomistic origin of high ductility and progressive failure of S-glass is derived from the reconstruction of the atomic structure, forming Mg-BO-Si interactions that delays fracture formation.

The crystallochemical role of malonate ions in coordination polymers

All compounds that contain malonate dianions C3H2O42-(mal2-) and atoms of d- or f-metals were analyzed. Dianions mal2-in structures of examined compounds reveal 17 topological types of coordination against metal atoms. Available data shows that mal2-more often form six-membered metal cycles which is the most abundant case for all 570 crystallographic sorts of analyzed mal2-(80%). For those mal2-which form six-membered metal cycles the average observed valence angle SSS is equal to 1200. Results of regression analysis of all mal2-showed linear dependence of ∠SSS on dihedral angel (φ) between planes which go through oxygen and carbon atoms of different carboxyl groups of one anion. For the equation ∠SSS = 124.9 – 0.207φ, correlation coefficient is -0.90. Discovered that in structures of crystals when φ < 600mal2-necessarily form six-membered metal cycles. Structural slackness of mal2-influence on characteristics of six-membered metal cycles formed by them. Those metal cycles usually have bath conformation. Coordination polymers with fixed type of metal atom and identical type of coordination of mal2-can have different dimension even in the absence of other linkers. This effect is evident on the example of [UO2(mal)(L)]·nH2O compounds. Reportedly [1], change of composition and structure of ligand L lead to changes in the system of intramolecular hydrogen bonds which influence on conformation of six-membered metal cycles. The change of conformation of this cycles lead to different relative spatial distribution of the three uranium atoms, connected with one mal2-. Although of the same stoichiometric composition and crystallochemical role of uranium atoms and coordinated ligand resulting polymeric groups [UO2(mal)(L)] in crystals have different dimension: 3D, 2D or 1D respectively for L – carbamide, water or dimethylacetamide. This work was supported by the base part of the government mandate of the Ministry of Education and Science of the Russian Federation.

Simulation of Formation Process of Conductive Organic Polymeric Materials for Gas Sensor Systems

In this work was carried out modeling of organic polymer materials for gas sensors on the example of a homogeneous polypyrrole and polyacrylonitrile with metal silver. The implementation was carried out by modeling the Wang-Landau and entropic Monte Carlo simulation based on a model with a fixed valence angle. To simulate the polymerization process using an algorithm based on the principles of irreversible aggregation of Eden. Methods of quantum chemistry has been investigated and the possibility of obtaining property silver-PAN and polypyrrole

General method for the description, visualization and comparison of metal coordination spheres: geometrical preferences, deformations and interconversion pathways

The coordination sphere geometry of metal atoms (M) in their complexes with organic and inorganic ligands (L) is often compared with the geometry of archetypal forms for the appropriate coordination number, n in MLn species, by use of the k = n( n− 1)/2 L—M—L valence angles subtended at the metal centre. Here, a Euclidean dissimilarity metric, Rc (x), is introduced as a one-dimensional comparator of these k-dimensional valence-angle spaces. The computational procedure for Rc (x), where x is an appropriate archetypal form (e.g. an octahedron in ML 6 species), takes account of the atomic permutational symmetry inherent in MLn systems when no distinction is made between the individual ligand atoms. It is this permutational symmetry, of order n!, that precludes the routine application of multivariate analytical techniques, such as principal component analysis (PCA), to valence angle data for all but the lowest metal coordination numbers. It is shown that histograms of Rc (x) values and, particularly, scatterplots of Rc (x) values computed with respect to two or more different appropriate archetypal forms (e.g. tetrahedral and square-planar four-coordinations), provide information-rich visualizations of the observed geometrical preferences of metal coordination spheres retrieved from, e.g. the Cambridge Structural Database. These mappings reveal the highly populated clusters of similar geometries, together with the pathways that map their geometrical interconversions. Application of Rc (x) analysis to the geometry of four- and seven-coordination spheres provides information that is at least comparable to, and in some cases is more complete than, that obtained by PCA.

Structure of N,4-dinitroaniline and its complex with sulfolane at 85 K; on the proton donor–acceptor affinity of the primary nitramine (HNNO2) group

The NNO2 group of the title compound is significantly less twisted with respect to the aromatic ring in comparison to a typical secondary nitramine. The amide nitrogen is trigonally hybridized. The nitramino group is almost planar. The C—C—N—N torsion angles vary between ca 13 and 42°, whereas the twist along the N—N bond is much smaller and amounts to between ca 1 and 15°. Those twist angles are governed by a crystal packing and are much larger in the case of crystals of pure N,4-dinitroaniline in comparison to that of its complex with sulfolane. The deviations of the internal angles of the aromatic ring from 120° do not exceed 3°. The presence of the nitro group increases the C—C—C valence angle of ca 2.0–2.6°, whereas an analogous effect associated with the nitramino group is much smaller (ca 0.3–1.3°), pointing to its weak electron-withdrawing properties. The nitramino group displays no tendency to conjugate with an electron-demanding substituent across the ring. It participates in hydrogen bonding only as a hydrogen-bonding donor. It does not act as a proton acceptor, despite the fact that nitramine rearrangement is catalysed by acids.

Spin-Orbit Coupling in Biradicals. 3. Heavy Atom Effects in Carbenes

CASSCF(8,6)/cc-pVDZ calculations of electron spin-spin dipole interaction tensor in the lowest triplet state of CH2, CHF, CHCl, and CHBr, spin-orbit coupling of each of the three sublevels with the lowest singlet, and the triplet zero-field-splitting parameters are reported as a function of the valence angle, with bond lengths optimized for the triplet state at the B3LYP/cc-pVTZ level of approximation. Both the one- and the two-electron parts of the spin-orbit coupling Hamiltonian are used, and the contributions to spin-orbit coupling provided by each atom and orbital pair in Weinhold's natural hybrid orbital basis are evaluated separately. This provides intuitive insight into the origin of spin-orbit coupling in carbenes and especially, the heavy atom effect of the substituent.