Journal of Structural Chemistry

Zhuravlev, Yu.; Korabel`nikov, D.

doi: 10.1134/S0022476617040011pmid: N/A

The crystal structures and electronic properties of magnesium and calcium nitrates, magnesium nitrate hexahydrate, and calcium nitrate tetrahydrate are studied at the density functional theory level by a hybrid functional in the basis set of localized atomic orbitals using the CRYSTAL14 program code. Atomic structural parameters, atomic charges, bond populations, energy and electron spatial distributions are calculated. The mainly electrostatic nature of interactions between nitro groups and water molecules is shown. The spectrum of the density of states of crystal hydrates, in comparison with nitrates, contains additional bands due to the presence of water. In the spectra of unoccupied states a gap is observed: the anionic gap is ~6.5 eV and the cationic gap is ~8.8 eV.

Madzhidov, T.; Gimadiev, T.; Malakhova, D.; Nugmanov, R.; Baskin, I.; Antipin, I.; Varnek, A.

doi: 10.1134/S0022476617040023pmid: N/A

By the structural representation of a chemical reaction in the form of a condensed graph a model allowing the prediction of rate constants (logk) of Diels–Alder reactions performed in different solvents and at different temperatures is constructed for the first time. The model demonstrates good agreement between the predicted and experimental logk values: the mean squared error is less than 0.75 log units. Erroneous predictions correspond to reactions in which reagents contain rarely occurring structural fragments. The model is available for users at https://cimm.kpfu.ru/predictor/.

Molani, F.; Askari, M.

doi: 10.1134/S0022476617040035pmid: N/A

The structural and electronic properties of semiconducting BC19 and AlC19 heterofullerenes as adsorbents for toxic small gas molecules (H2S and SO2) are determined by DFT. Structural parameters, energy gaps, natural population analysis, partial density of state, dipole moments, and vibrational frequencies were extracted. The adsorption process and sensitivity to the gases are increased by doping with B or Al. The results show that AlC19 is the most sensitive structure. The good sensing of AlC19 is related to high charge transfer upon gas adsorption. Adsorption of the H2S on the BC19 has negligible effects on the electronic properties, to be categorized as “harmless adsorption”. H2S is weakly adsorbed on BC19 and AlC19. The H2S and SO2 molecules act as electron donating and electron withdrawing molecules, respectively. Notably, the adsorption processes are highly exothermic. In general, BC19 is more reactive than C20 and AlC19 is the most reactive cage. This provides a theoretical basis to fabricate B- and Al-doped C20-based gas sensors.

Zhang, L.-J.; Wu, S.-Y.; Kuang, M.-Q.; Hu, X.-F.; Li, G.-L.

doi: 10.1134/S0022476617040047pmid: N/A

The spin Hamiltonian parameters (g factors, hyperfine structure constants and superhyperfine parameters) and local structures for Ag2+ centers in AgCl and KCl crystals are theoretically studied using the high-order perturbation formulas for a tetragonally elongated 4d 9 cluster. The impurity centers undergo relative elongations (≈0.05 Å and 0.23 Å for Ag2+ in AgCl and KCl, respectively) along the C 4 axis owing to the Jahn–Teller effect. All the calculated spin Hamiltonian parameters show good agreement with the experimental data, and the ligand contributions to the spin Hamiltonian parameters are important and should be taken into account. The unpaired spin densities in the superhyperfine parameters are determined from molecular orbital coefficients based on the cluster approach, instead of being taken as the adjustable parameters in the previous treatments. Increasing tetragonal elongation from AgCl to KCl is attributed to a decrease in chemical bonding (or lower force constant) with increasing Ag2+–Cl distance.

Yang, Y.; Fang, Y.; Liu, Q.; Yang, L.; Hu, S.; Hu, S.; Wang, D.; Zhang, H.; Luo, S.

doi: 10.1134/S0022476617040059pmid: N/A

Extraction complexes of Eu(III) and Am(III) with two 2,6-dicarboxypyridine diamide-type ligands L–A and L–B (Fig. 1) are studied by density functional theory (DFT). At both B3LYP/6-31G(d)/RECP and MP2/6-31G(d)/RECP levels of theory, the geometrical optimizations of the structures of the complexes can achieve the same accuracy and obtain the same geometrical configuration. At the B3LYP/6-311G(d,p)/RECP level of theory Eu3+ and Am3+ prefer to form [ML]3+ complexes under the solvation conditions, and the Am(III) complexes with L–A are more stable than the corresponding Eu(III) complexes. In the system with the ligand L–B, both [ML]3+ and [ML(NO3)3] species are very unstable.

Güneş, E.; Parlak, C.; Şenyel, M.

doi: 10.1134/S0022476617040060pmid: N/A

Halogen and solvent effects on the conformational, vibrational, and electronic characteristics of thiophene-2-carbaldehyde (T2C, C5H4OS) and thiophene-2-carbonyl-halogens [C5H3XOS, X = F (T2C-F), Cl (T2C-Cl), and Br (T2C-Br)] are analyzed by the density functional theory (DFT) and time dependent density functional theory (TDDFT), using the B3LYP functional and the 6-31++G(d,p) basis set. Computations consider two conformations of the compounds in both gas phase and solution. The present study aims at the exploration of the halogen and medium effects on the stability, structural parameters, dipole moment, carbonyl stretching vibration, frontier molecular orbitals, ultraviolet (UV) and density-of-states spectra of the conformers. The atypical characteristics of fluorine and chlorine affecting the electrical-optical band gaps, chemical hardness, partial density-of-states plot, absorption band, and the highest occupied molecular orbital are observed correspondingly. The findings of this research will provide insight for future studies considering conformations analogous to the compounds studied.

Zemnukhova, L.; Udovenko, A.; Makarenko, N.; Kuznetsov, S.; Babushkina, T.

doi: 10.1134/S0022476617040072pmid: N/A

(NH4)Sb4F13 crystals (I) are synthesized and their crystal structure (tetragonal crystal system: a = 9.6431(2) Å, c = 6.5503(2) Å, V = 609.11(3) Å3, Z = 2, d calc = 4.100 g/cm3, F(000) = 664, space group I4̅) is determined. The main structural units of I are tetranuclear anionic [Sb4F13]− complexes and [NH4]+ cations. The anionic complexes are built of four SbF3 groups linked together by tetrahedral bridging fluorine atom. At room temperature the (NH4)Sb4F13 crystals are isostructural to previously studied МSb4F13 (М = K, Rb, Cs, and Tl). The study of 121,123Sb NQR spectra of compound I is performed in a range of 77-370 K, which shows that when the temperature decreases (<250 K) the substance exhibits piezoelectric properties, as do other compounds of this group, but with a violation of their isostructurality.

Li, G.-L.; Wu, S.-Y.; Kuang, M.-Q.; Hu, X.-F.; Xu, Y.-Q.

doi: 10.1134/S0022476617040084pmid: N/A

The g factors for Cu2+ in meta-zeunerite (Cu(UO2)2(AsO4)2·3H2O), kroehnkite (Na2Cu(SO4)2·2H2O), copper benzoate (Cu(PhCO2)2·3H2O) and diaboleite (Pb2Cu(OH)4Cl2) of the tetragonal phase are uniformly treated by high order perturbation formulas for 3d 9 ions in tetragonally elongated octahedra. The calculation results are in good agreement with the observed values and systematically analyzed in view of the local structures around Cu2+. The g anisotropies Δg (= g ‖−g ⊥) are largely ascribed to the local tetragonal elongations of the Cu2+ sites, characterized by the relative elongation ratios (R ‖−R ⊥)/R̅ ≈ 19%, 21%, 27% and 30% for metazeunertie, kroehnkite, copper benzoate and diaboletie, respectively. The anomalous valley (minimum) of relative g anisotropy for copper benzoate is attributed to the modification of the Cu2+ electronic states due to the phenyl ring. The ligand orbital contributions are found to be significant due to covalency, and should be taken into account. The present study would be helpful to the unified investigations of structures and properties of the copper oxygen compounds.

Krasnykh, E.; Portnova, S.

doi: 10.1134/S0022476617040096pmid: N/A

The work proposes a method to predict changes in the heat capacity of the liquid—vapor phase transition Δ l g Ср 0 (298.2) based on modified Randič indices for alkanes and acyclic oxygen-containing compounds: alcohols, aldehydes, ketones, ethers, and esters. Based on the obtained Δ l g Ср 0 (298.2) values heat capacities in the liquid phase Cp liq 0 (298.2) are calculated for the compounds under study.

Kartsev, V.; Shtykov, S.; Pankin, K.

doi: 10.1134/S0022476617040102pmid: N/A

The work analyzes both literature data on the dependence of the internal liquid pressure on thermodynamic parameters of state and theoretical ideas of the nature of the internal pressure. The analysis enables the formulation of a hypothesis: the temperature coefficient of the internal liquid pressure corresponds to the state of its force field and the dynamics of this coefficient follows the course of changes in the macroscopic force field of liquids. The hypothesis underlies the construction of a scale of states of the own force field of liquids. To substantiate this scale, and consequently, the formulated hypothesis, the scale is verified with respect to water. A unified scale of states of force fields of associated liquids is proposed.