An approximate analytical expression is proposed for calculating the probability of phonon-assisted tunneling of charge carriers between deep centers (traps) in dielectrics and wide-bandgap semiconductors. It is shown that the discrepancy between the proposed approximation and the exact integral expression is orders of magnitude smaller than that of the previously known approximation. It is demonstrated that, with the increasing electric field, it becomes energetically more favorable for the charge carrier, instead of direct energetic excitation, to transfer part of the potential energy to the phonon subsystem before the tunneling act.

Взаимодействие каликс[4]аренов HCA и AdCA с катионами марганца(II) в присутствии молекул 2,2’-бипиримидина привело к образованию новых схожих по строению тетраядерных {MnII2MnIII2} кластеров, структура которых была охарактеризована в кристаллической фазе с помощью монокристального РСА. Рассмотрено влияние двух факторов на деформацию кластерного ядра, показано, что введение 2,2’-бипиримидина в качестве солиганда приводит к уменьшению расстояния MnII-MnII, а при введении объемных п-адамантильных групп в структуру каликс[4]арена наблюдается увеличение расстояния MnIII-MnIII. Кроме этого, наличие объёмных заместителей «верхнего обода» каликс[4]арена AdCA вызывает изменения во взаимном расположении молекул комплексов в кристалле, приводящие к образованию пористой кристаллической упаковки.

Aliphatic amines containing N-heterocyclic fragments reacted with dialkyl [3,5-di-tert-butyl-4-oxo-2,5-cyclohexadienylidene)methyl] phosphonates to form 1,6-nucleophilic addition products. This approach was used to obtain α-aminophosphonates containing sterically hindered phenol and N-heterocyclic fragments in high yields. All the compounds were evaluated for their in vitro cytotoxicity with various cancer cell lines by MTT assay method. In the course of biological studies, it was found that the obtained compounds possess cytotoxic activity against some tumor cells.

New 2-(4-carboxyphenylhydrazinylidene)[1,3]thiazolo[3,2-a]pyrimidine derivatives were synthesized in high yields by the reactions of 5-aryl-6-ethoxycarbonyl-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine with 4-carboxyphenyldiazonium chloride. The azo coupling occurs at the 2 position of the substrate. Different types of intra- and intermolecular non-covalent interactions can affect the supramolecular assembly of the molecules in the crystal structures and the molecular configuration of the synthesized compounds. The combined contribution of supramolecular non-covalent interactions leads to several types of the self-assembly in the crystalline phase, such as hydrogen-, chalcogen-, and π—π-bonded racemic dimers. In the case of compounds containing the m-chlorophenyl substituent at the C(5) position of the thiazolo[3,2-a]-pyrimidine scaffold, these interactions lead to the formation of halogen-bonded homochiral chains. Due to the π—π stacking between the electron-rich thiazolopyrimidine scaffold and the electron-deficient carboxyphenyl moiety, there occurs the formation of dense layers in the solid phase when selecting the appropriate substituents at the C(5) atom. The crystallization conditions (vapor diffusion and slow evaporation) were found to influence the configuration of the C=N-arylhydrazone moiety.

Among the seven-membered ketals of pyridoxine containing hydroxymethyl groups in various positions of the pyridine ring, an unusual ability of selenium dioxide to catalyze the reaction of nucleophilic substitution of the hydroxyl group by N,O-nucleophiles was found. Quantum chemical calculations have shown the possibility of the formation of selenium dioxide adducts with substrates and the formation of reactive intermediates—ortho- and para-pyridinone methides. The antioxidant and antimycotic activity of the obtained compounds was determined.

New crystalline {(Mn2Mn2III)-Mn-II} tetranuclear cluster is prepared by the interaction of manganese(II) chloride with calix[4]arene 3 functionalized at the upper rim by distal p-(4-nitrophenyl)diazenyl and p-tert-butyl groups displaying different electronic effects and sizes. The structure of the cluster is studied by single-crystal XRD. Due to the presence of (4-nitrophenyl)diazenyl moieties at the upper rim of the macrocyclic ligand, the molecules of the tetranuclear {(Mn2Mn2III)-Mn-II} clusters are involved in pi-stacking interactions leading to the formation of 2D supramolecular layers affording a porous crystal packing.

New crystalline {Mn_2^IIMn_2^III} tetranuclear cluster is prepared by the interaction of manganese(II) chloride with calix[4]arene 3 functionalized at the upper rim by distal p-(4-nitrophenyl)diazenyl and p-tert-butyl groups displaying different electronic effects and sizes. The structure of the cluster is studied by single-crystal XRD. Due to the presence of (4-nitrophenyl)diazenyl moieties at the upper rim of the macrocyclic ligand, the molecules of the tetranuclear {Mn_2^IIMn_2^III} clusters are involved in π-stacking interactions leading to the formation of 2D supramolecular layers affording a porous crystal packing.

The synthesis and characterization of previously unknown azides, iminophosphoranes and amines from commercially available mucochloric and mucobromic acids is reported. The reaction of 5-alkoxy-3,4-dihalo-2(5H)-furanones with sodium azide resulted in the regioselective formation of furanone 4-azidoderivatives. A series of novel iminophosphoranes was obtained from the reaction of corresponding azides with triphenylphosphine. Reduction of iminophosphoranes with stannous chloride dihydrate led to the heterocycles, possessing an amino group at the C4 carbon atom of the unsaturated γ-lactone ring.

The electronic structure of oxygen vacancies in lanthanum-doped hafnium oxide (HfO2:La) is studied using the density functional theory. The simulation is carried out for the optimal structure of HfO2:La in three crystalline phases for an oxygen vacancy involved in the impurity charge compensation that is structural element, as well as for a second purposely added oxygen vacancy. It is shown that the HfO2 doping with La increases the oxygen vacancy content in such a way that the twice positively charged vacancy concentration increases and the neutral one decreases. The doping with La facilitates new oxygen vacancies formation in HfO2. Oxygen vacancies in HfO2:La and HfO2 have a similar electronic structure and are traps for electrons. However, the deeper trap and the electrostatic repulsion caused by the impurity in HfO2:La suppress the vacancies participation in the charge transport. Based on the obtained results, the mechanisms of HfO2-based resistive and ferroelectric memory improvements, when HfO2 doped with lanthanum, are discussed.

It is assumed that the reliability and functionality of nonvolatile memory elements based on MgO are determined by the charge transport in MgO. In the present study, the type of MgO conductivity is established using experiments on the injection of minority charge-carriers in the n(p)-Si/MgO/Mg structures. It is shown that electrons and holes contribute to the MgO conductivity, causing bipolar charge transport. Using ab initio simulations, it was found that native point defects in MgO can provide both electron and hole conductivity.

An approach to the stereoselective oxidation of 5,6-bis(hydroxymethyl)-2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridine and 5,6-bis(hydroxymethyl)-2,4-dimethyl-3-hydroxypyridine with manganese dioxide has been developed, intermediates and by-products have been isolated. In solutions, pyridoxine derivatives containing a carbaldehyde group exist in cyclic hemiacetal and open hydroxyaldehyde forms.

Взаимодействие каликс[4]арена 3, содержащего на верхнем ободе различные по электронному эффекту и размеру дистально расположенные п-(4-нитрофенил)диазенильные и п-трет-бутильные группы, с хлоридом марганца (II) привело к образованию тетраядерного {MnII2MnIII2} кластера в кристаллической фазе, структура которого была охарактеризована с помощью монокристального РСА. Благодаря наличию (4-нитрофенил)диазенильных фрагментов на верхнем ободе макроциклического лиганда, молекулы тетраядерного {MnII2MnIII2} кластера вступают в π-стэкинг взаимодействия, ведущие к образованию 2D супрамолекулярных слоёв, которые при упаковке в кристалле образуют пористую структуру.

The reaction of 3,3',5,5'-tetrabromo-4,4'-bipyridine (BrBipy) with cobalt nitrate and terephthalic acid (H2Bdc) gave 2D and 3D metal-organic frameworks {[Co2(Bdc)2(BrBipy)2(H2O)4] · 4DMF} (I) and {[Co2(Ddc)4(BrDipy)] · · 2MeOH} (II), respectively. The structure of the complexes was studied by X-ray diffraction (CCDC nos. 2259216 (I) and 2259214) (II)).

A mechanism of transverse charge transfer through hexagonal boron nitride (h-BN) in a MIS structure has been studied. Experimental data for charge transfer have been analyzed in terms of different models of charge transfer in insulators. It has been shown that charge transfer in h-BN is described by the model of phonon-assisted tunneling between neutral traps. The thermal and optical energies of phonon-coupled traps in h-BN have been determined. Based on charge transfer measurements, XPS spectra, and the ab initio electronic structure of intrinsic defects in h-BN it has been found that boron–nitrogen divacancies are most probably responsible for charge transfer in h-BN and transfer is provided by electrons.

A new convenient method for the preparation of dichlorodinitro-2,1,3-oxadiazole-1-oxide (dichlorodinitrobenzofuroxan) has been developed. Composition and structure of the prepared dichlorodinitrobenzofuroxan have been elucidated by a set of chemical, physical, and physico-chemical methods and also confirmed for the first time via single crystal X-ray diffraction analysis. Thermal stability of the compound has been investigated using a method of combined thermogravimetry and differential scanning calorimetry.

A new method for the synthesis of 6-hydroxypyridoxine and its seven-membered acetals has been developed. The synthesized compounds have high antioxidant activity, which is not inferior to the reference drugs, i.e., ascorbic acid and trolox. The seven-membered ketal of 6-hydroxypyridoxine effectively penetrates the cytoplasmic membrane of cells.

New bis-chelate cobalt(II) complex [Co(DPG) 2 (DMF) 2 ] ( 1 ), where DPG is N -(2,5-bis(methoxycarbonyl)phenyl)-α-diphenylphosphorylglycinate, has been prepared and characterized. The complex is the first example of cobalt complex containing phosphorylated derivative of α-amino acid. Octahedral coordination geometry of the cobalt complex 1 has been determined by X-ray diffraction. Electrochemical reduction of the obtained complex has been found to be irreversible two-electron process ( E_p^red = –1.70 V vs Ag/AgNO 3 , 1 × 10 –2 М in CH 3 CN), resulting in formation of cobalt metal adsorbed on the surface of working electrode.

Redox properties of bis(1-naphtylimino)acenaphthene have been studied using various voltammetry techniques. Radical anion of diimine ligand has been obtained in situ through electrochemical reduction, and its optical properties have been studied. A new sodium complex having the anion-radical form of bis(1-naphthylimino)-acenaphthene has been obtained and structurally characterized. We have found that the solvent nature affects the long-wavelength absorption band of the sodium complex, which is determined by the contribution of the coordinated solvent molecules to the lowest unoccupied molecular orbital (LUMO) energy.

The low-stable organonickel sigma-complex (2,2'-bipyridyl)bromo(2,4,6-tricyclopentylphenyl)nickel(II) [NiBr(Tcpp)(bpy)] was obtained by a modified procedure of preparative electrochemical synthesis and isolation. The crystal structure of the resulting organonickel complex was determined by the X-ray diffraction method. Its structure was compared with that of its more stable analogue [NiBr(Tchp)(bpy)], where Tchp is 2,4,6-tricyclohexylphenyl. It was found that a more efficient network of intermolecular interactions is formed in the [NiBr(Tchp)(bpy)] crystal, which is responsible for its higher stability, whereas [NiBr(Tcpp)(bpy)] is more likely to enter into an equilibrium Schlenk reaction, leading to its decomposition.