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Molecular structure calculations of heteroligand macrotetracyclic complexes of 3d elements MIV (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) with phthalocyanine as the (NNNN) donor-atom ligand and two fluoride anions were carried out in terms of the density functional theory with the OPBE functional and the TZVP basis set. The key bond lengths, bond angles, and non-bond angles in the complexes are presented. The standard enthalpies, entropies, and Gibbs energies of formation of the compounds are calculated. According to calculations, all complexes have tetragonal bipyramidal or similar structures. The complex-forming agent MIV lies in the plane formed by the donor nitrogen atoms of the phthalocyanine ligand. The M-N bond lengths as well as the M-F bond lengths are equal to one another. All six-membered metal chelate rings in the complexes are identical to one another both in terms of the sum and the set of the bond angles. The same holds for the five-membered rings containing nitrogen atoms.

Molecular structure calculations of macrotetracyclic metal complexes containing a scan-dium(III) ion, a macrocyclic (N,N,N,N)-donor ligand (porphyrazine, trans-dibenzoporphyrazine, tetrabenzoporphyrazine), and a F− anion were carried out at the OPBE/TZVP level of the density functional theory. The most important bond lengths, bond angles, and non-bond angles in these heteroligand metal complexes were determined. All complexes have distorted tetragonal-pyramidal structures where the complex-forming agent ScIII is above the basal plane formed by the donor nitrogen atoms. The distance between the ScIII atom and the basal plane somewhat decreases in the order porphyrazine—trans-dibenzoporphyrazine—tetrabenzopor-phyrazine. Although all six-membered metal chelate rings in each complex are identical to one another, none of them is planar; on the contrary, all five-membered rings are planar. The standard enthalpies, entropies, and Gibbs energies of formation of the metal complexes in question were determined. Different metal complexes are characterized by different numerical values of the same thermodynamic parameters.

The possibility for tetra-, hexa-, octa-, and decanitrogen to exist was analyzed using the QCISD(T)/TZVP and G4 quantum chemical calculations. The results obtained suggest the existence of only four allotropes of nitrogen whose molecules contain from four to eight atoms, viz., rectangular and tetrahedral N4, open-book N6, and cubic N8. The bond lengths and bond angles were calculated for all compounds, as well as selected thermodynamic parameters (standard enthalpy of formation ΔfHo, standard entropy of formation So, standard Gibbs energy of formation ΔfGo) of the compounds in the gas phase. The enthalpies and entropies of the oxidation reactions of each compound by molecular oxygen were calculated using the results of quantum chemical computations. All the oxidation reactions are highly exothermic and practically irreversible; therefore, the title allotropes of nitrogen may appear to be promising combustible materials.

Molecular structure calculations of heteroligand (6666)macrotetracyclic metal (MIV) chelates (M = Fe, Co, Ni, Cu) with trans-di[benzo]porphyrazine as the (N,N,N,N)-donor ligand and two F− anions were carried out at the OPBE/TZVP level of density functional theory. The key bond lengths, bond angles, and non-bond angles in the complexes were determined and corresponding standard enthalpies, entropies, and Gibbs energies of formation were calculated. All complexes have slightly distorted tetrahedral structures. The complex-forming agent MIV lies in the plane formed by the donor nitrogen atoms. The metal—nitrogen bonds are usually pair-wise equal. The six-membered metal chelate rings in the complexes are identical to one another from the standpoint of both the sum and set of the bond angles.

Using the density functional theory (DFT) in the OPBE/TZVP//QZP level, the geometric parameters and total energies of the molecular structures of macrotricyclic complexes of 3d and 4d elements with the so-called open contour, which can arise during template synthesis between M(II) of the indicated elements, dithiooxamide H2N–C(=S)–C(=S)–NH2 and glyoxal HC(=O)–CH(=O), were calculated. Based on the data of this calculation, it was established that, depending on the nature of the d-element M(II), both theoretically admissible variants of coordination of this ligand to M(II) can be realized – through four nitrogen atoms [(NNNN)-coordination] or two nitrogen atoms and two sulfur atoms [(NSSN)-coordination]. It was noted that as a result of the formation of coordination compounds with M(II) ions of 3d- and 4d-elements with both (NNNN)- and (NSSN)-coordination of the ligand, a decrease in the degree of distortion of the spatial structure of the macrocycle formed by this ligand, takes place in comparison with that of the parent ligand. At the same time, the metal complexes formed by it, are for the most part either practically flat or exhibit a small (within 5°) deviation from coplanarity. Exceptions are only complexes Cr(II), Mo(II), Ru(II), and Pd(II) with the (NSSN)-coordination of the ligand. By DFT OPBE/TZVP//QZP method, the geometric parameters and total energies of the molecular structures of macrotricyclic complexes of 3d and 4d elements with the socalled open contour, which can arise during template synthesis between M(II) of the indicated elements,dithiooxamide H2N–C(=S)–C(=S)–NH2 and glyoxal HC(=O)–CH(=O), were calculated.

Various mechanisms of the primary act of gas-phase monomolecular thermal decomposition of nitrobenzene were studied theoretically. The following reactions were considered: radical decomposition with dissociation of the C-N bond, nitro-nitrite rearrangement to trans-phenyl nitrite and cis-phenyl nitrite, elimination of nitrous acid, as well as formation of 6(S)-7-oxa-8-azabicyclo[4.2.0]octa-1(8),2,4-triene 8-oxide were studied theoretically. Calculations were carried out for different temperatures using a number of density functional theory methods (B3LYP, wB97XD, CAM-B3LYP, MN12L, and PBE0) and basic sets (6-31G(d,p) and 6-31+G(2df,p)). The transition state of homolytic dissociation of the C-N bond was localized using the method of search for the structure corresponding to maximum value of the Gibbs free energy along the reaction coordinate. The structure thus found was used to evaluate the rate constants and the activation parameters at different temperatures. It was shown that not only radical decomposition, but also isomerization to trans-phenyl nitrite (at low temperatures) and cis-phenyl nitrite (at high temperatures) can contribute to the effective rate constant.

The IR spectra of p-(3-carboxy-1-adamantyl)thiacalix[4]arene (1-AdCOOHTC4A) have been studied. IR spectra of crystalline 1-AdCOOHTC4A obtained at room temperature or upon heating to 250 °C or its dilute solutions lack bands of free hydroxyl groups. The frequency of hydroxyl groups at 3377 cm−1 indicates the formation of an intramolecular H-bond along the lower rim of the 1-AdCOOHTC4A molecule. On the top edge of thiacalixarene, the carboxyl groups form dimeric or cyclic tetrameric complexes via intermolecular H-bonds. The conformation of the cone persists, but there is a mutual influence of H-bonds along the upper and lower rims of the thiacalix[4]arene molecule. The structure with dimer H-bonds between carboxyl groups is 31.9 KJ/mol less preferable than the conformation with tetramer cyclic H-bonds for 1-AdCOOHTC4A. Comparison of the absorption band of νOH alcohol hydroxyl groups in the IR spectra of 1-AdCOOHTC4A at 3377 cm−1, with the corresponding band of 1-AdTC4A at 3372 cm−1, suggests that the presence of the second system of H-bonds of carboxyl groups in the first molecule does not affect the H-bond of alcohol hydroxyl groups.

By using DFT method in the OPBE/TZVP level, key parameters of molecular structures of five-atomic heteronuclear clusters having Al2M3 composition where M = Mn or Zn (bond lengths, bond angles, and torsion (dihedral) angles) have been calculated. It has been found that the first of these clusters exist in 25 modifications different substantially in their total energy whereas the second, in 14 modifications. Also, it has been noted that the molecular structures of Al2Mn3 and Al2Zn3 differ very significantly between each other both in terms of geometric parameters and in external form; in addition, the most stable modifications of these metal clusters differ between them rather considerably in geometric form, too.

By using DFT method in the OPBE/TZVP level, key parameters of molecular structures of five-atomic heteronuclear clusters having Al2M3 composition where M = Fe or Cu (bond lengths, bond angles, and torsion (dihedral) angles) have been calculated. Each of these clusters was found to exist in eight modifications different substantially in their total energy. It has been noted that, in general, the molecular structures of Al2Fe3 and Al2Cu3 differ very significantly between each other both in terms of geometric parameters and in external form; nevertheless, the most stable modifications of these metal clusters are externally similar and differ only in the number of M–M bonds.

The density functional theory methods were used to demonstrate that during the thermal decomposition of o-nitrotoluene, with the formation of 5-methylene-6-aci-nitrocyclohexa- 1,3-diene (aci-form) being the primary event, the rotation of the =N(O)OH group around the CN double bond in the aci-form is of key importance. The activation enthalpy is lower for this step than for the alternative process of H atom transfer between the O atoms in this group. This accounts for the competitive formation of the experimentally observed products of о-nitrotoluene thermal decomposition, namely, the hydroxyl radical and water. The activation barriers of the reactions were estimated over a broad temperature range, which indicated the possible contribution of о-nitrotoluene thermal decomposition and other alternative primary event mechanisms (nitro—nitrite rearrangement, bicyclization) to the efficient rate constant. The results account for the differences between the activation parameters experimentally determined at various temperatures by different authors.

Processes of mild template synthesis occurring in systems 3d-element ion MII—(N,S)-, (N,O,S)-ambidentate ligson A—monoor dicarbonyl ligson B in gelatin-immobilized matrices are considered and discussed. The chemical nature of the final products of template synthesis formed under these specific conditions is compared with the chemical nature of the final products formed by template synthesis in solutions. In many cases, the nature and chemical composition of the products differ substantially. Specific features of the DFT calculated molecular structures of the macrocyclic compounds that could be formed due to the template synthesis in the systems indicated above are discussed.

The geometric parameters of the macrotricyclic CoII, NiII, CuII, and ZnII chelates with (NSSN) coordination of the donor centers of the ligand, which are formed by complex formation between the metal ions, hydrazinomethane thioamide H2N-HN-C(=S)-NH2, and butane-2,3-dione Me-C(=O)-C(=O)-Me in aqueous solutions and gelatin-immobilized matrix implants, were calculated using the DFT B3LYP hybrid method in the 6-31G(d) standard basis set and the Gaussian03 program. The bond lengths, bond and torsion angles in the coordination compounds are presented. All the complexes are nearly planar.

Experimental and theoretical conformational analysis of polyfunctional 2-substituted nitroethenes was carried out by the method of dipole moments and density functional theory calculations. It was established that the nitro and ester (or trichloromethyl) groups are trans-arranged in the molecules of 2-trichloromethyl-(ethoxycarbonyl)-1-nitro- and 1-bromo-1-nitroethenes, i.e., nitroalkenes have E-configuration, their bromo-containing analogues have Z-configuration, and s-cis-orientation of the C=C and C=O double bonds is preferred for nitroacrylates. 2,3-Dibromo-3-nitroacrylates have untrivial Z-configuration in solution.

The equilibrium geometric parameters, enthalpies of formation of molecular and radical species, and dissociation energies of the C-N bond at 0 and 298 K were determined by the B3LYP density functional method for nitroethane, fluoronitroethanes, chloronitroethanes, and mixed fluorochloronitroethanes. Trends in variation of the geometric and electronic parameters of the molecules, enthalpies of formation, and dissociation energies were discussed.

Semiempirical, ab initio, and density functional theory calculations were used to study the primary act of gas-phase monomolecular decomposition of certain C-nitro compounds and their radical cations, associated with the nitro-nitrile rearrangement. It was shown that the reaction fails to occur with all neutral molecules of aliphatic nitro compounds (except for fluoronitromethane and fluoronitroethene) and has a much lower barrier with the corresponding radical cations. An important role of the nitro-nitrile rearrangement in gas-phase decomposition of aromatic nitro compounds was demonstrated.

According to the results of ab initio quantum-chemical calculation 1-bis(dimethylamino)-4-bis(trimethylsilyl-2,3-diphosphabuta-1,3-diene exists as an E-isomer where electronic delocalization occurs involving donor dimethylamino and acceptor trimethylsilyl groups and also the multiple P = C bonds.

We previously [1] studied the structure of 1,3,2benzodioxaphosphinan-4-ones by X-ray analysis, by IR spectroscopy, and by measuring their dipole moments. Regardless of the aggregate state, the phosphorus-containing heteroring with planar fragments exists preferentially in a flattened sofa conformation and that the exocyclic substituent occupies axial (N C O, NEt 2 ) or equatorial (Cl) position. In the present work we performed theoretical conformational analysis of 1,3,2-benzodioxaphosphinan-4-ones I IV by nonempirical B3LYP/6-31G(d) quantum-chemical calculations.