Nataliya V. Tverdova

The geometric structure of molecular species existing in vapors over solid "Ag(piv) – M" systems (where M = Ga (Texp = 489(10) K), In (Texp = 451(5) K), piv=2,2-dimethylpropanoate) was determined using the in situ method by synchronous gas electron diffraction/mass spectrometry (GED/MS). A combined analysis of experimental data and quantum chemical calculations revealed that the vapor of the "Ag(piv) – Ga" system contains a single molecular form, Ga(piv)3. The complex exhibits structural flexibility due to torsional vibrations of the tert-butyl groups. Using Ga(piv)3 as an example, the influence of the internal rotation of the tert-butyl groups on the diffraction pattern and the parameters of the thermally averaged rg-configuration of the complex was demonstrated. For the "Ag(piv) – In" system, vapor models corresponding to the formation of gaseous complexes in which indium has different oxidation states InI(piv), InIInIII(piv)4 and InIII(piv)3 were tested. For this purpose, quantum chemical calculations DFT/B3LYP, PBE0 of the geometric and electronic structure of the complexes, theoretical radial distribution functions, and Gibbs free energies of the heterophase reactions of the formation of the specified indium complexes were performed. Analysis of the obtained data led to the conclusion that in the system with an excess of silver pivalate, the formation of a gaseous indium pivalate complex of the composition InIII(piv)3 with C3 symmetry is most likely. Experimental geometric parameters of gaseous Ga(piv)3 and In(piv)3 complexes were compared with parameters calculated using the DFT method. It was found that the parameters of the MO6 coordination polyhedron are better reproduced using the PBE0 functional.

Based on the data of the gas electron diffraction/mass spectrometry (GED/MS) experiment, the composition of the vapor over rhenium tetrafluoride at T = 471 K was established, and it was found that species of the Re₂F₈ is present in the gas phase. The geometric structure of the Re₂F₈ molecule corresponding to D_4h symmetry was found, and the following geometric parameters of the r_h1 configuration were determined: r_h1(Re-Re) = 2.264(5) Å, r_h1(Re-F) = 1.846(4) Å, α(Re-Re-F) = 99.7(0.2)°, φ(F-Re-Re-F) = 2.4 (3.6)°. Calculations by the self-consistent field in full active space approximation showed that for Re₂F₈, the wave function of the ¹A_1g ground electronic state can be described by the single closed-shell determinant. For that reason, the DFT method was used for a structural study of Re₂X₈ molecules. The description of the nature of the Re-Re bond was performed in the framework of Atom in Molecules and Natural Bond Orbital analysis. The difference in the experimental values of r(Re-Re) in the free Re₂F₈ molecule and the [Re₂F₈]²⁻ dianion in the crystal corresponds to the concept of a triple σ²π⁴ (Re^IV-Re^IV) bond and a quadruple σ²π⁴δ² (Re^III-Re^III) bond, respectively, which are formed between rhenium atoms due to the interaction of d-atomic orbitals. The enthalpy of dissociation of the Re₂F₈ molecular form in two monomers ReF₄ (Δ_dissH°(298) = 109.9 kcal/mol) and the bond energies E(Re-Re) and E(Re-X) in the series Re₂F₈→Re₂Cl₈→Re₂Br₈ molecules were estimated. It is shown that the Re-Re bond energy weakly depends on the nature of the halogen, while the symmetry of the Re₂Br₈ (D_4d) geometric configuration differs from the symmetry of the Re₂F₈ and Re₂Cl₈ (D_4h) molecules.

By DFT method with B3LYP, PBE, CAM-B3LYP, and B97D functionals, it was found that the molecule 4-(4-tritylphenoxy)phthalonitrile (TPPN) has four conformers. The geometric structure, vibrational frequencies, electronic characteristics, and thermodynamic functions of conformers, as well as the structure and energy of transition states, were determined. IR spectrum of TPPN film contains vibrational bands belonging to different conformers. The assignment of bands was performed basing the distribution of normal vibration energy on internal coordinates. A synchronous electron diffraction/mass spectrometric experiment was performed to determine the structure of conformers in a saturated TPPN vapor. The elemental composition of the ions recorded in the mass spectrum indicates the thermal stability of TPPN at least up to T = 200 °C. The difference in the structure of tetrasubstituted metal phthalocyanines, which can be synthesized from different TPPN conformers, has been shown.

Электронное и геометрическое строение, силовое поле и колебательный спектр молекулы трис-ацетилацетоната марганца в электронных состояниях с мультиплетностью M = 1, 3 и 5 были изучены с помощью квантово-химических расчетов, выполненных методом DFT/UB3LYP при использовании корреляционно-согласованного набора базисных функций cc-pVTZ. Структура молекулы в высокоспиновом состоянии S=2 (тип симметрии электронного состояния ⁵B) и с типом симметрии равновесной конфигурации С₂ характеризуется наименьшей энергией. При этом, координационный полиэдр MnO₆ имеет форму вытянутого октаэдра. Высокоспиновое состояние ⁵A соответствует седловой точке на ППЭ, при этом координационный полиэдр приобретает форму сжатого октаэдра. Искажение октаэдрической структуры координационного полиэдра значительно, и этот факт свидетельствует о проявлении сильного эффекта Яна-Теллера (вибронного эффекта) в электронном состоянии ⁵E. Расчеты для низко-спинового состояния с S=0 завершились получением неожиданного результата. Оптимизация структуры симметрии С₂ для электронного состояния ¹B привела к структурным параметрам молекулы, близким к параметрам, полученным для электронного состояния ³A₂. При этом межъядерные расстояния Mn-O в пределах 0,001 Å оказались совпадающими с расстояниями, полученными для структуры D₃-симметриии со спином S=1. Этот результат соответствует ситуации, когда два электрона заселяют разные орбитали 1е, обладая противоположными спинами. Электронные состояния ³A₂ и ¹B лежат выше, чем высокоспиновое состояние на 5,2 и 17,3 ккал/моль, соответственно. Заселенность молекулярных орбиталей находится в хорошем согласии с предсказаниями теории кристаллического поля, свидетельствуя о том, что d-орбитали иона Mn³⁺ подвергаются заметному воздействию поля лигандов. Для цитирования: Бергер Р.Й.Ф., Гиричев Г.В., Гиричева Н.И., Петрова А.А., Слизнев В.В., Твердова Н.В. Молекулярная структура трис-ацетилацетоната марганца в разных спиновых состояниях. Изв. вузов. Химия и хим. технология. 2017. Т. 60. Вып. 4. С. 47-53.

1,8-Bis(phenylethynyl)anthracene (1,8-BPEA) was synthesized by a twofold Kumada cross-coupling reaction. The molecular structure of 1,8-BPEA was determined using a combination of gas-phase electron diffraction (GED), mass spectrometry (MS), quantum chemical calculations (QC) and single-crystal X-ray diffraction (XRD). Five rotamers of the molecule with different orientations of phenylethynyl groups were investigated by DFT calculations. According to these, molecules of C₂ symmetry with co-directional rotation of the phenylethynyl groups are predicted to exist in the gas phase at 498 K. This was confirmed by a GED/MS experiment at this temperature. The bonding of this conformer was studied and described in terms of an NBO-analysis. Dispersion interactions in the solid state structure and in the free molecule are discussed. In the solid this symmetry is broken; the asymmetric unit of the single crystal contains 3.5 molecules and a herringbone packing motif of π-stacked dimers and trimers. The π-stacking in the dimers is between the anthracene units, and the trimers are linked by π-stacking between phenyl and anthracene units. The interaction between these stacks can be described in terms of σ(C–H)⋯π interactions.

The molecular structure of chromium and cobalt tris-acetylacetonates is studied by the synchronous electron diffraction and mass spectrometric experiment and quantum chemically. It is found that...