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Using three different versions of the density functional theory (DFT) – B3PW91/TZVP, M06/TZVP and OPBE/TZVP chemical models, the calculation of the molecular structures of (6666) macrocyclic complexes of 3d-elements (M) with a novel (NNNN)-donor macrocyclic ligand, 2,3,5,7,8,10,12,13,15,17,18,20-dodecaazaporphin (H2L), was carried out. The values of the most important bond lengths, bond and non-bond angles in these metal complexes were presented. The standard enthalpy, entropy, and Gibbs energy of formation of these compounds were also calculated. It was noted that according to the data of the above chemical models, [MnL], [FeL], [CoL], [NiL], and [CuL] complexes with this novel ligand have a flat MN4 chelate node and a planar structure as a whole, while the [TiL], [VL], [CrL] and [ZnL] complexes have a non-coplanar MN4 chelate node. Moreover, all 6-membered rings in each of these metal chelates are identical to each other (both in terms of the sum of the bond angles included in them and in their assortment); adjoining 5-membered cycles for the majority of M are also identical to each other (non-identity is noted only in the cases M = Ti, Mn, as well as for the original 2,3,5,7,8,10,12,13,15,17,18,20-dodecaazaporphin). A good agreement was also noted between similar parameters calculated by various DFT methods, both qualitatively and quantitatively.

The possibility of the existence of the unknown iron complex containing phthalocyanine and two oxygen atoms in the inner coordination sphere was predicted using DFT quantum chemical calculation (OPBE/TZVP and B3PW91/TZVP levels). The structural parameters, the ground state multiplicity, the NBO analysis results, and the standard thermodynamic parameters for complex formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] are represented.

Based on the results of a quantum chemical calculation using the DFT method in the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of a cobalt heteroligand complex containing in the inner coordination sphere tetra[benzo]derivative of porphyrazine (phthalocyanine), oxide (O[Formula: see text] and fluoride (F[Formula: see text] ions, with possible oxidation state of Co(V) that is non-characteristic for the given 3[Formula: see text]-element, has been shown. The data on the structural parameters, multiplicity of the ground state, NBO analysis data and standard thermodynamic parameters of formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] for the indicated complex have been presented. At the same time, it has been noted that the porphyrazine itself as well as di[benzo]porphyrazine, do not form such metalcomplexes.

By using quantum chemical calculation data obtained by the DFT method with the B3PW91/TZVP and OPBE/TZVP levels, the possibility of the existence of three Fe(V) complexes, each of which contains in the inner coordination sphere porphyrazine/trans-di[benzo]porphyrazine/tetra[benzo]porphyrazine (phthalocyanine), oxygen (O2−) and fluorine (F−) ions, was shown. Key geometric parameters of the molecular structure of these heteroligand complexes are given; it is noted that FeN4 chelate nodes, and all metal-chelate and non-chelate cycles in each of these compounds, are practically planar with the deviation from coplanarity, as a rule, by no more than 0.5°. Furthermore, the bond angles between two nitrogen atoms and an Fe atom are equal to 90°, or less than this by no more than 0.1°, while the bond angles between donor atoms N, Fe, and O or F, in most cases, albeit insignificantly, differ from this value. Nevertheless, the bond angles formed by Fe, O and F atoms are exactly 180°. It is shown that good agreement occurs between the structural data obtained using the above two versions of the DFT method. NBO analysis data for these complexes are presented; it is noted that, according to both DFT methods used, the ground state of the each of three complexes under consideration may be a spin quartet or spin doublet. Additionally, standard thermodynamic parameters of formation (standard enthalpy ∆fH0, entropy S0 and Gibbs’s energy ∆fG0) for the macrocyclic compounds under consideration are calculated.

Based on the results of a quantum chemical calculation using the DFT method in the OPBE/TZVP and B3PW91/TZVP, the possibility of the existence of a copper heteroligand complex with trans-di[benzo]derivative of 3,7,11,15-tetraazaporphine (trans-di[benzo]porphyrazine) and two oxygen (O[Formula: see text] ions that is still unknown for this element was shown. In addition, the data on the structural parameters, the multiplicity of the ground state, NBO analysis and standard thermodynamic parameters of formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] for this complex are presented.

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.

The polarity and structure of tri(1- or 2-naphthyl)phosphines and their chalcogenides were determined by the methods of dipole moments, IR spectroscopy, and DFT quantum-chemical calculations at the B3PW91/6-311++G(df,p) level of theory. In solution, tri(1-naphthyl)phosphine prefers a single conformer with a gauche,gauche,gauche orientation of the substituents at the phosphorus. Tri(2-naphthyl)phosphine, as well as both phosphine chalcogenides exist as equilibrium mixtures of several forms with a propeller arrangement of the substituents and a cis or gauche orientation of the Csp2‒Csp2 and P=X (X = LEP, O, S, Se) bonds.

Quantum-chemical calculation of the molecular structures of potential isomeric (NNNN)- donoratomic macrocyclic tetradentate ligands, cis- and trans-di[benzo]porphyrazines, was carried out using the density functional theory (DFT) B3PW91/TZVP. It is noted that the first of these compounds can exist in four forms [so-called ([Formula: see text]-isomers], differing from each other by the mutual orientation of hydrogen atoms bonded to the nitrogen atoms, while the second compounds take the form of two similar isomers. The values of the most important bond lengths, bond and non-bond angles in each of these ([Formula: see text] -isomeric compounds, as well as the values of their relative energy, standard enthalpy, entropy, and Gibbs energy of formation are presented. It was found that the most stable among both cis- and trans-di[benzo]porphyrazines is the ([Formula: see text]-isomer with the trans-orientation of hydrogen atoms bonded to nitrogen atoms, while the ([Formula: see text] -isomers with cis-oriented hydrogen atoms for both of these compounds had significantly higher relative energies.

Using a theoretical approach supported by DFT calculations, the features of molecular structure of isomer 17418 (C1) of fullerene C76 with the distribution of single, double and delocalized π-bonds...

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.

Using various versions of density functional theory (DFT), DFT M06/TZVP, DFT B3PW91/TZVP, DFT OPBE/TZVP, and, partially, the MP2 method, the possibility of the existence of 3

Based on the results of a quantum chemical calculation using the DFT B3PW91/TZVP, MP2/TZVP and MP3/TZVP levels, the possibility of the existence of carbon–nitrogen compounds having the unusual carbon : nitrogen ratio 1 : 12, which is unknown for these elements at present, was shown. Data on the structural parameters are presented; it was shown that all CN4 groupings are strictly planar. In addition, the bond lengths formed by nitrogen atoms and a C atom are equal to each other, and the bond angles formed by nitrogen atoms and a C atom are equal to 90.0°, or practically do not differ from this value. Thermodynamical parameters, NBO analysis data and HOMO/LUMO images for this compound are presented, too. Good agreement was found between the calculated data obtained using the above three quantum-chemical methods.

Conformational analysis of tris(4-methylphenyl)phosphine and its oxide, sulfide, and selenide has been performed by the dipole moment method and DFT quantum chemical calculations at the B3PW91/ 6-311++G(df,p) level of theory. The title compounds have been found to exist in solution as a single symmetrical conformer with gauche,gauche,gauche orientation of the substituents on the phosphorus atom with respect to the P=X bond (X = LEP, O, S, Se).

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.

DFT quantum chemical calculations at the B3PW91/6-31G(d) level of theory have shown that the addition of secondary phosphine sulfides and phosphine selenides with alkyl, phenyl, and phenylalkyl substituents to pentyl vinyl and hexyl vinyl selenides follows a molecular mechanism against the Markovnikov rule through energetically favorable eight-membered transition state, leading to the formation of tertiary phosphine chalcogenides. Secondary phosphine selenides are more reactive than the corresponding phosphine sulfides.

The molecular structures of (6666) macrotetracyclic (M(IV) chelates (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) with the (NNNN)-donor ligand porphyrazine and the oxo ligand have been calculated by the DFT OPBE/TZVP method. Selected bond lengths and bond and nonbonded angles in the complexes have been reported. The standard enthalpies, entropies, and Gibbs energies of formation of these compounds have been calculated. All these complexes have a structure of a distorted tetragonal pyramid, where the complex-forming M(IV) atom is located above the base formed by the donor nitrogen atoms. It has been demonstrated that all six-membered metal chelate rings in each of these structures are identical to each other both in the sum of their bond angles and in their set, although none of them is flat. The images of the molecular structures of some of these coordination compounds are presented.

The molecular structures of heteroligand (6666)macrotetracyclic chelates of M(III) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Cu) with porphyrazine (an (NNNN)-donating ligand) and F– ion are calculated by the DFT OPBE/TZVP method. The key bond lengths, bond angles, and nonbonded angles in these complexes are reported. The standard enthalpies, entropies, and Gibbs free energies of formation are calculated for the complexes. All complexes have a slightly distorted tetragonal-pyramidal geometry, where the complex former M(III) is to some degree raised above the pyramid base made up of the donor nitrogen atoms. Characteristically, all 6-membered metal chelate rings in these metal chelates are identical to one another both in terms of the sum of bond angles and in their varieties.

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.

The standard thermodynamic parameters of formation (ΔfH°(298 K), ΔfS°(298 K), and ΔfG°(298 K)) for p,d-metal clusters of Al2M3 (M = 3d) stoichiometry and the standard enthalpy, entropy, and Gibbs free energy of their formation reactions from monoatomic species in the gas phase were calculated by the hybrid density functional (DFT) method in OPBE/TZVP approximation and Gaussian09 software. Such reactions were found to be exothermic with an enthalpy factor, and the thus-formed heteronuclear metal clusters are distinguished by a high thermal stability. Both the individual thermodynamic characteristics of the considered metal clusters and the thermodynamic parameters of their formation reactions were found to have intricate variation dynamics depending on the nature of 3d element.

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.

Quantum-chemical calculation of most important parameters of molecular and electronic structures of octa-carbon C8 having cubic form (bond lengths, bond and torsion angles) using CCSD(T)/QZVP and DFT B3PW91/QZVP methods, has been carried out. NBO analysis data and HOMO/LUMO images for this compound are presented, too. Good agreement was found between the structural data obtained using the above two quantum-chemical methods and, also, with corresponding experimental data. Also, the standard thermodynamic parameters of formation of cubic C8 considered here, and namely standard enthalpy ΔfH0(298K), entropy Sf0(298K) and Gibbs’ energy ΔfG0(298K) of formation for this compound were calculated. By using this data, a theoretically possible variant of the synthesis of this compound by dehydrogenation of cubane C8H8 is considered, and the thermodynamic characteristics of each of the four stages of this process have been calculated. It is noted that each of the four stages of this process is characterized by a very high (about 500 kJ/mol) enthalpy of activation, as a result of that, for their realization within a sufficiently short time, the use of appropriate catalysts is necessary.

Based on the results of a quantum chemical calculation using the DFT B3PW91/TZVP, MP2/TZVP and MP3/TZVP levels, the possibility of the existence of carbon-nitrogen compounds having the unusual carbon : nitrogen ratio 1 : 12, which is unknown for these elements at present, was shown. Data on the structural parameters are presented; it was shown that all CN

Experimental and theoretical conformational analysis of N-methyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, N-butyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, and N-octyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide was carried out by the methods of dipole moments, IR spectroscopy, and Density Functional Theory (DFT) B3PW91/6-311++G(df,p) calculations. In solution, these N,N-dialkyl substituted bisphosphorylated acetamides exist as a conformational equilibrium of several forms divided into two groups—with Z- or E-configuration of the carbonyl group and alkyl substituent, and syn or anti arrangement of the phosphoryl-containing fragments relative to the amide plane. The substituents at the phosphorus atoms have eclipsed cis- or staggered gauche-orientation relative to the P=O groups, and cis orientation of the substituents is due to the presence of intramolecular H-contacts P=O...H−Cphenyl or p,π conjugation between the phosphoryl group and the phenyl ring. Preferred conformers of acetamides molecules are additionally stabilized by various intramolecular hydrogen contacts with the participation of oxygen atoms of the P=O or C=O groups and hydrogen atoms of the methylene and ethylene bridges, alkyl substituents, and phenyl rings. However, steric factors, such as a flat amide fragment, the bulky phenyl groups, and the configuration of alkyl bridges, make a significant contribution to the realization of preferred conformers.

Based on the quantum-chemical calculation using the Density Functional Theory (DFT) method, the existence possibility of zinc heteroligand complexes with porphyrazine and its analogs – trans-di[ben...

The molecular structures of macrotetracyclic M(II) (M = Mn, Fe, Co, Ni, Cu, or Zn) chelates with a 17-membered tetradentate macrocyclic ligand with the (NNNN) coordination of donor centers, containing one 5-membered, one 8-membered, and two 6-membered chelate rings were calculated by the DFT OPBE/TZVP method. Most important bond lengths, bond angles, and nonbonding angles in the complexes are reported. The standard enthalpy, entropy, and Gibbs free energies were calculated for these complexes. Prominent non-coplanarity is intrinsic to all complexes, both in chelate cores MN4 and in chelate rings. In each of the complexes the 5-membered chelate ring has a relatively small non-coplanarity, the 8-membered chelate ring has considerable non-coplanarity, and 6-membered rings are intermediate in this regard, being quite strongly differentiated in their degrees of non-coplanarity.

Based on the results of a quantum chemical calculation using the DFT method, the possibility of the existence of a copper heteroligand complex with porphyrazine and two fluoride ions with an oxidation state of IV that is unusual for this element has been shown. Also, data on the structural parameters and multiplicity of the ground state of this complex have been presented.

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.

Based on the results of a quantum chemical calculation using the DFT method, the possibility of the existence of a zinc heteroligand complex with 3,7,11,15-tetraazaporphine and fluoride ion with an oxidation state of Zn(III), unusual for the given element, is shown. Data on the structural parameters and multiplicity of the ground state of this complex are also presented.

Conformational analysis of Se-esters of diselenophosphinic acids has been performed and their polarities have been determined using the methods of dipole moments and quantum chemistry (DFT [B3PW91/6-311++G(df,p)]+CPCM). In solution, the studied compounds exist as an equilibrium of several conformers with staggered gauche and trans- or eclipsed cis-orientation of the substituents relative to the P=Se bond. The presence of eclipsed cis-conformations is explained by the formation of intramolecular H⋯Se bonds involving the hydrogen atom of the Se-alkyl(benzyl) or phenyl substituents at the phosphorus atom and the selenium atom of the P=Se group.

Quantum-chemical DFT OPBE/TZVP method with the Gaussian09 program package have been used to calculate bond angles in the macrocycles of 1,8-dioxa-3,6,10,13-tetraazacyclotetradecanetetrathione-4,5,11,12, 1,8-dithia-3,6,10,13-tetraazacyclotetradecanetetrathione-4,5,11,12, and 1,3,5,8,10,12-hexaazacyclotetradecanetetrathione-6,7,13,14 and their complexes with Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) ions with (NNNN) coordination of the donor sites of the ligand forming upon the complexation in the ternary M(II)–ethanedithioamide—formaldehyde and M(II)–ethandithioamide–2-thiapropanediol-1,3 systems and in the quaternary M(II)–ethanedithioamide—formaldehyde—ammonia system in gelatin-immobilized matrix implants. It has been noticed that the macrocycle is considerably distorted in both the macrocyclic compounds (this distortion can be quantitatively characterized by the degree of deviation of the macrocycle from coplanarity) and in their complexes (more than 60°). Depending on the nature of both the M(II) ion and the macrocyclic ligand, this distortion can become weaker or stronger.

According to DFT calculations, hydrolysis of 1,1,1-trisubstituted hyposilatranes and hypogermatranes proceed in one stage and have lower activation energies than hydrolysis of the corresponding atranes and ocanes, and, unlike what is observed with the tricyclic and bicyclic analogs, the former reactions are characterized by positive Gibbs energies. The configuration of the hydrolysis products is stabilized by the transannular interactions N→X and O→X (X = Si, Ge) and intramolecular hydrogen bonding.

The geometries of (5665)macrotetracyclic Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) complexes with the NNNN-coordination of the chelant donor sites and the MN4 chelate core, which can be formed through template processes in the M(n)-2-[(2-formylphenyl)amino]benzenecarbaldehyde-4,5-diaminoacridone have been calculated by the hybrid DFT OPBE/TZVP method with the Gaussian 09 program package. The bond lengths, bond angles, and selected nonbonded angles in these complexes have been determined. It has been demonstrated that none of the chelate rings is strictly planar although these rings in all complexes, except the Co(II) complex, are pairwise identical. The six-membered rings are more noncoplanar than the five-membered rings. The standard enthalpies, entropies, and Gibbs energies of formation of these compounds have been calculated.

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 the density functional theory (DFT) method at the OPBE/QZVP level, key parameters of molecular structures of six-atomic (heterobi)nuclear metal clusters with an AlnFem composition (n + m = 6) (bond lengths, bond angles, and torsion (dihedral) angles) were calculated. It was found that each of these clusters exists in a large number of structural isomers that differ substantially in terms of their total energy. Furthermore, the molecular structures of these structural isomers significantly differ regarding the geometric parameters and geometric form. In addition, the most stable structural isomers of these metal clusters also differ rather considerably in terms of the geometric form.

Based on the results of a quantum chemical calculation using the DFT method with the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of three cobalt heteroligand complexes containing in the inner coordination sphere porphyrazine, di[benzo]- and tetra[benzo]porphyrazine, and two oxygen (O2&minus, ) ions with probable oxidation state VI of Co, which is unknown for this element at the present time, was shown. Data on the structural parameters are presented. It was shown that CoN4 chelate nodes as well as all metal-chelate and non-chelate cycles in each of these complexes, were strictly planar. Besides, the bond angles formed by two donor nitrogen atoms and a Co atom were close or equal to 90&deg, while the bond angles formed by donor atoms N, Co, and O, in most cases, albeit insignificantly, differed from this value. Good agreement between the calculated data obtained using the above two versions of the DFT method was found. Standard thermodynamic parameters of formation (standard enthalpy &Delta, H0f, 298, entropy S0f, 298 and Gibbs&rsquo, s energy &Delta, G0f, 298) for the indicated complexes were presented too.

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

Using the data of a quantum chemical modeling of molecular structures obtained by the density functional theory (DFT), the possibility of the existence of a copper macrocyclic complexes with 3,7,11,15-tetraazaaporphine, trans-di[benzo] 3,7,11,15-tetraazaaporphine or tetra[benzo] 3,7,11,15-tetraazaaporphine and oxide anion where oxidation state of copper is IV, was shown. The values of the parameters of molecular structures and NBO analysis for such complexes were presented, too.

The mechanism of reactions of silatranes and germatranes, and their bicyclic and monocyclic analogues with one molecule of methanol or ethanol, was studied at the Density Functional Theory (DFT) B3PW91/6-311++G(df,p) level of theory. Reactions of 1-substituted sil(germ)atranes, 2,2-disubstituted sil(germ)ocanes, and 1,1,1-trisubstituted hyposil(germ)atranes with alcohol (methanol, ethanol) proceed in one step through four-center transition states followed by the opening of a silicon or germanium skeleton and the formation of products. According to quantum chemical calculations, the activation energies and Gibbs energies of activation of reactions with methanol and ethanol are close, their values decrease in the series of atranes&ndash, ocanes&ndash, hypoatranes for interactions with both methanol and ethanol. The reactions of germanium-containing derivatives are characterized by lower activation energies in comparison with the reactions of corresponding silicon-containing compounds. The annular configurations of the product molecules with electronegative substituents are stabilized by the transannular N&rarr, X (X = Si, Ge) bond and different intramolecular hydrogen contacts with the participation of heteroatoms of substituents at the silicon or germanium.

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.

The hybrid density functional theory (DFT) method in the OPBE/TZVP approximation and the Gaussian 09 program were used to calculate the geometric parameters of the molecular structures of aluminum copper and aluminum silver metal clusters with the stoichiometric compositions Al2Cu3 and Al2Ag3. It was found that each of the clusters can exist as eight structural forms, which considerably differ in the stability and geometrical parameters. The bond lengths and bond and torsion (dihedral) angles were determined for each form.

The IR spectra of p-(3-carboxy-1-adamantyl)-calix[4]arene (AdC4A) were studied. Using IR spectroscopy, it has been shown that in calixarene in dilute solution in CCl4, there was no free hydroxyl absorption band. The hydroxyl group band was characterized by a very low frequency, which indicates a strong intramolecular hydrogen bond on the lower rim of the calixarene molecules. On the upper rim of the calixarene, the carboxyl groups form cyclic dimer or tetramer complexes via intermolecular hydrogen bonds. The cone conformation persists, but there is a mutual influence of the hydrogen bonds along the top and bottom rims of the calixarene molecule. The structure with dimeric hydrogen bonds between the carboxyl groups is 16.5 KJ/mol more preferable than the structure with tetrameric cyclic hydrogen bonds for AdC4A. The reactivity depends on the type of association on the upper rim, whether these are hydrogen-bonded dimers or cyclic tetrameric association.

The quantum-chemical calculation of iron, cobalt and nickel heteroligand complexes with the double deprotonated form of (NNNN)-donor atomic ligand&mdash, 3,7,11,15-tetraazaporphine&mdash, and two oxo ligands has been carried out. Data on the structural and standard thermodynamic parameters, NBO analysis and multiplicity of the ground states of these complexes have been presented. The given calculation has been made by using the density functional theory (DFT) method with the OPBE/TZVP basis set. Based on the results of this calculation, the possibility of the existence of oxidation state VI for the chemical elements indicated above&mdash, unusual for iron and cobalt, and for nickel, unknown at all&mdash, has been shown.

Conformational analysis of tris(3-methylphenyl)phosphine and its chalcogenides has been performed by methods of dipole moments, IR spectroscopy, and quantum chemistry [DFT B3PW91/6-31G(df,p)]. In solution, these compounds exist as an equilibrium of conformers with gauche- and cis-arrangement of the substituents at the phosphorus atom relative to the P=X bond (X = lone electron pair, O, S, Se).

The molecular structures of (5454)macrotetracyclic M(II) chelates with a tetradentate (NNNN)- donor ligand formed through template reactions in the ternary systems M(II)–1,2-ethandiamine (H2N–CH2–CH2–NH2)–trioxosulfidosulfate(VI) anion (SO3S(2)–), where M = Mn, Fe, Co, Ni, Cu, and Zn, have been calculated by the density functional theory OPBE/TZVP method. The bond lengths and selected bond and nonbonded angles in these complexes have been determined. Standard enthalpies, entropies, and Gibbs energies of formation of these compounds have been calculated.

The geometries of (5676)macrotetracyclic Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) complexes with the (NNNN) coordination of the chelant donor sites, formed through template processes in the M(II)–3,3,8,8-tetramethyl-4,7-diazadecanedihydrazone-1,10-butanedione-2,3 systems have been calculated by the DFT OPBE/TZVP method with the Gaussian 09 program package. The bond lengths and angles and selected nonbonded angles in these complexes with the MN4 chelate core have been determined. It has been demonstrated that none of the chelate rings is planar: the smallest deviation from coplanarity is always observed for the five-membered rings and the largest, for the six-membered rings not identical to each other. The seven-membered ring resulting from the template cross-linking exhibits deviations from coplanarity intermediate between those for the five- and six-membered rings.